CN115002485A - Image encoding method, image decoding method and related device - Google Patents

Abstract

The embodiments of the present application disclose an image encoding method, an image decoding method, and a related device. The image decoding method includes: dividing an image, determining a chrominance component intra prediction mode of a current encoding block; according to the chroma component intra prediction mode , determining the prediction block of the chrominance component of the current coding block; performing prediction modification on the prediction block of the chrominance component of the current coding block to obtain the modified prediction block of the chrominance component of the current coding block. In the chrominance component intra prediction mode in the embodiments of the present application, the spatial correlation between adjacent coding blocks and the current coding block is used to correct the prediction samples of the chrominance components of the current coding block, so as to improve the prediction accuracy and coding efficiency.

Description

Image coding method, image decoding method and related device

technical field

The present application relates to the technical field of electronic devices, and in particular, to an image encoding method, an image decoding method, and related apparatuses.

Background technique

Digital video capabilities can be incorporated into a wide range of devices, including digital television, digital broadcast systems, wireless broadcasting systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-books Readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones, video conferencing devices, video streaming devices, and the like.

Digital video devices implement video compression techniques such as those provided by MPEG-2, MPEG-4, ITU-TH.263, ITU-TH.264/MPEG-4 Part 10 Advanced Video Coding (AVC), ITU- A standard defined by the TH.265 high efficiency video coding (HEVC) standard and those video compression techniques described in extensions to the standard to transmit and receive digital video information more efficiently. Video devices may transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing these video codec techniques.

With the proliferation of Internet video, despite the continuous evolution of digital video compression technology, it still puts forward higher requirements for video compression ratio.

SUMMARY OF THE INVENTION

Embodiments of the present application provide an image encoding method, an image decoding method, and a related device, so as to use the spatial correlation between adjacent encoding blocks and the current encoding block to correct the prediction samples of the chrominance components of the current encoding block, so as to improve the prediction accuracy and performance. coding efficiency.

In a first aspect, an embodiment of the present application provides an image encoding method, including: dividing an image, determining a chrominance component intra prediction mode of a current encoding block; determining the current encoding block according to the chroma component intra prediction mode The predicted block of the chrominance component of the current coding block is predicted and modified to obtain the modified predicted block of the chrominance component of the current coding block.

Compared with the prior art, in the chrominance component intra prediction mode, the solution of the present application uses the spatial correlation between adjacent coding blocks and the current coding block to correct the prediction samples of the chrominance components of the current coding block, so as to improve the prediction accuracy and performance. coding efficiency.

In a second aspect, an embodiment of the present application provides an image decoding method, including: parsing a code stream to determine a chroma component intra prediction mode of a current decoding block; and determining the current decoding mode according to the chroma component intra prediction mode A prediction block of the chrominance component of the block; performing prediction modification on the prediction block of the chrominance component of the current decoding block to obtain the modified prediction block of the chrominance component of the current decoding block.

Compared with the prior art, in the chrominance component intra prediction mode, the solution of the present application uses the spatial correlation between adjacent coding blocks and the current coding block to correct the prediction samples of the chrominance components of the current coding block, so as to improve the prediction accuracy and performance. decoding efficiency.

In a third aspect, an embodiment of the present application provides an image encoding apparatus, including:

a dividing unit, used for dividing the image, and determining the intra prediction mode of the chrominance component of the current coding block;

a determining unit, configured to determine a prediction block of the chrominance component of the current coding block according to the chrominance component intra prediction mode;

A modification unit, configured to perform prediction modification on the prediction block of the chrominance component of the current coding block to obtain the modified prediction block of the chrominance component of the current coding block.

In a fourth aspect, an embodiment of the present application provides an image decoding apparatus, including:

a parsing unit for parsing the code stream and determining the intra prediction mode of the chrominance component of the current decoding block;

a determining unit, configured to determine a prediction block of the chrominance component of the current decoding block according to the chrominance component intra prediction mode;

A modification unit, configured to perform prediction modification on the prediction block of the chrominance component of the current decoding block to obtain the modified prediction block of the chrominance component of the current decoding block.

In a fifth aspect, an embodiment of the present application provides an encoder, including: a processor and a memory coupled to the processor; the processor is configured to execute the method described in the first aspect.

In a sixth aspect, an embodiment of the present application provides a decoder, including: a processor and a memory coupled to the processor; the processor is configured to execute the method described in the second aspect above.

In a seventh aspect, an embodiment of the present application provides a terminal, where the terminal includes: one or more processors, a memory, and a communication interface; the memory and the communication interface are connected to the one or more processors; The terminal communicates with other devices through the communication interface, and the memory is used for storing computer program code, the computer program code including instructions, when the one or more processors execute the instructions, the terminal executes The method of the first aspect or the second aspect.

In an eighth aspect, embodiments of the present application provide a computer-readable storage medium, where instructions are stored in the computer-readable storage medium, and when the instructions are executed on a computer, the computer is made to execute the first aspect or the second the method described in the aspect.

In a ninth aspect, an embodiment of the present application provides a computer program product containing instructions, when the instructions are run on a computer, the instructions cause the computer to execute the method described in the first aspect or the second aspect.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

1 is a schematic block diagram of a coding tree unit in an embodiment of the application;

2 is a schematic block diagram of a color format in an embodiment of the application;

3 is a schematic block diagram of a CTU and a coding unit CU in an embodiment of the present application;

4 is a schematic block diagram of an associated pixel of a coding unit in an embodiment of the present application;

5A is a schematic block diagram of a luminance component intra prediction mode in an embodiment of the present application;

5B is a schematic diagram of a common intra prediction mode of chrominance components in an embodiment of the present application;

6 is a schematic block diagram of adjacent pixels used for calculation of coefficients of a linear model in an embodiment of the present application;

7 is a schematic block diagram of a downsampling filter in an embodiment of the present application;

8 is a schematic block diagram of a change from a luminance component reconstruction block to a chrominance component prediction block in an embodiment of the present application;

9 is a schematic block diagram of a video decoding system in an embodiment of the present application;

10 is a schematic block diagram of a video encoder in an embodiment of the present application;

11 is a schematic block diagram of a video decoder in an embodiment of the application;

12A is a schematic flowchart of an image encoding method according to an embodiment of the present application;

12B is a schematic diagram of a downsampling process in a horizontal direction in an embodiment of the present application;

12C is a schematic diagram of a downsampling process in a vertical direction in an embodiment of the present application;

12D is a schematic diagram of a bidirectional downsampling process in an embodiment of the present application;

13 is a schematic flowchart of an image decoding method in an embodiment of the present application;

14 is a block diagram of a functional unit of an image encoding apparatus in an embodiment of the application;

15 is a block diagram of another functional unit of the image encoding apparatus in the embodiment of the application;

16 is a block diagram of a functional unit of an image decoding apparatus in an embodiment of the application;

FIG. 17 is a block diagram of another functional unit of the image decoding apparatus in the embodiment of the present application.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

It will be understood that the terms "first", "second", etc., as used herein, may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, a first client could be referred to as a second client, and similarly, a second client could be referred to as a first client, without departing from the scope of this disclosure. Both the first client and the second client are clients, but they are not the same client.

First, terms and related technologies used in the embodiments of the present application are introduced.

For image division, in order to represent video content more flexibly, the High Efficiency Video Coding standard (HEVC) technology defines a coding tree unit (CTU), a coding unit (CU), prediction Unit (Prediction Unit, PU) and Transform Unit (Transform Unit, TU). CTU, CU, PU and TU are all image blocks.

Coding tree unit CTU, an image is composed of multiple CTUs, a CTU usually corresponds to a square image area, including the luminance pixels and chrominance pixels in this image area (or may only contain luminance pixels, or may only contain The CTU also includes syntax elements, which indicate how to divide the CTU into at least one coding unit (coding unit, CU), and a method for decoding each coding unit to obtain a reconstructed image. As shown in FIG. 1, an image 10 is composed of a plurality of CTUs (including CTU A, CTU B, CTU C, etc.). The encoding information corresponding to a certain CTU contains the luminance value and/or the chrominance value of the pixels in the square image area corresponding to the CTU. In addition, the encoding information corresponding to a certain CTU may also contain syntax elements indicating how to divide the CTU into at least one CU, and a method of decoding each CU to obtain a reconstructed image. An image area corresponding to one CTU may include 64×64, 128×128 or 256×256 pixels. In one example, a 64x64 pixel CTU contains a rectangular pixel lattice of 64 columns of 64 pixels, each pixel containing a luma component and/or a chrominance component. A CTU can also correspond to a rectangular image area or an image area of other shapes, and an image area corresponding to a CTU can also be an image area with a different number of pixels in the horizontal direction and the number of pixels in the vertical direction, for example, including 64×128 pixels .

Coding unit CU, usually corresponds to an A×B rectangular area in the image, including A×B luminance pixels or/and its corresponding chrominance pixels, A is the width of the rectangle, B is the height of the rectangle, A and B can be the same It can also be different. The values of A and B are usually integer powers of 2, such as 128, 64, 32, 16, 8, and 4. The width involved in the embodiments of the present application refers to the length along the X-axis direction (horizontal direction) in the two-dimensional rectangular coordinate system XoY shown in FIG. 1 , and the height refers to the two-dimensional rectangular coordinate system XoY shown in FIG. 1 . The length along the Y-axis direction (vertical direction) in the middle. The reconstructed image of a CU can be obtained by adding the predicted image and the residual image. The predicted image is generated by intra-frame prediction or inter-frame prediction. Specifically, it can be composed of one or more prediction blocks (PB). The transform coefficients are generated by performing inverse quantization and inverse transform processing, and may specifically be composed of one or more transform blocks (transform blocks, TB). Specifically, a CU includes encoding information, and the encoding information includes information such as prediction mode and transform coefficients. According to the encoding information, the CU is subjected to corresponding decoding processing such as prediction, inverse quantization, and inverse transformation, and a reconstructed image corresponding to the CU is generated.

The prediction unit PU is the basic unit of intra prediction and inter prediction. The motion information that defines the image block includes inter prediction direction, reference frame, motion vector, etc. The image block that is being encoded is called the current coding block (CCB), and the image block that is being decoded is called the current decoding block. (current decoding block, CDB), for example, when prediction processing is being performed on an image block, the current coding block or current decoding block is the prediction block; when residual processing is being performed on an image block, the current coding block or current decoding block is the transform block . The picture in which the current coding block or the current decoding block is located is called the current frame. In the current frame, the image blocks located on the left or upper side of the current block may be inside the current frame and have completed the encoding/decoding process to obtain the reconstructed image, which are called reconstructed blocks; the encoding mode of the reconstructed block, reconstructed pixels, etc. Information is available. A frame that has completed encoding/decoding before the current frame is encoded/decoded is called a reconstructed frame. When the current frame is a unidirectional prediction frame (P frame) or a bidirectional prediction frame (B frame), it has one or two reference frame lists respectively, and the two lists are called L0 and L1 respectively, and each list contains at least one reconstructed frame. frame, referred to as the reference frame for the current frame. The reference frame provides reference pixels for inter prediction of the current frame.

The transform unit TU processes the residuals of the original image block and the predicted image block.

Pixels (also known as pixels) refer to pixels in an image, such as pixels in coding units, pixels in luminance component pixel blocks (also known as luminance pixels), and pixels in chrominance component pixel blocks. (also known as chroma pixels), etc.

The sample (also known as pixel value) refers to the pixel value of the pixel point. The pixel value in the luminance component domain specifically refers to the luminance (ie, the grayscale value), and the pixel value in the chrominance component domain specifically refers to the chrominance value. (ie color and saturation), according to different processing stages, the samples of a pixel include original samples, predicted samples and reconstructed samples.

In intra-frame prediction, a predicted image of the current block is generated according to the spatially adjacent pixels of the current block. An intra prediction mode corresponds to a method of generating a predicted image. The division of the intra prediction unit includes 2N×2N division and N×N division. The 2N×2N division method is to not divide the image block; the N×N division method is to divide the image block into four sub-images of equal size. piece.

Generally, the digital video compression technology works on video sequences whose color coding method is YCbCr, which may also be called YUV, and whose color format is 4:2:0, 4:2:2 or 4:4:4. Among them, Y represents the brightness (Luminance or Luma), that is, the grayscale value, Cb represents the blue chrominance component, Cr represents the red chrominance component, and U and V represent the chrominance (Chrominance or Chroma), which is used to describe color and saturation. Spend. In the color format, 4:2:0 means that every 4 pixels has 4 luminance components and 2 chrominance components (YYYYCbCr), and 4:2:2 means that every 4 pixels has 4 luminance components and 4 chrominance components. component (YYYYCbCrCbCr), and 4:4:4 represents full pixel display (YYYYCbCrCbCrCbCrCbCr), Figure 2 shows the distribution of each component in different color formats, where the circle is the Y component and the triangle is the UV component.

During digital video encoding, the encoder reads and encodes the pixels of the original video sequence in different color formats. General digital encoders usually include prediction, transformation and quantization, inverse transformation and inverse quantization, loop filtering, and entropy coding, etc., to eliminate spatial, temporal, visual, and character redundancy. However, the human eye is more sensitive to changes in luminance components, and does not respond strongly to changes in chrominance components, so the YUV 4:2:0 color format is generally used for encoding in the original video sequence. At the same time, the digital video encoder adopts different prediction processes for the luminance component and the chrominance component in the intra-frame coding part. The prediction of the luminance component is more detailed and complicated, while the prediction of the chrominance component is usually relatively simple. Cross Component Prediction (CCP) mode is a technology in existing digital video coding that acts on luminance and chrominance components to improve the video compression ratio.

The cross-component prediction mode implementation process works in intra-frame coding, the method includes using the training samples of the Luminance Block to determine a Linear Model for predicting the Chrominance Block, and using the Luminance Block block samples and a linear model to determine the chroma block samples. Among them, the luminance block and the chrominance block are the pixel blocks of the coding unit in the luminance component and the chrominance component. The digital video encoder usually reads the original video sequence into a frame-by-frame image and divides the image into coding tree units (CTUs). , and the coding tree unit can be further divided into coding units CU of different and the same size. The specific coding process is performed in coding units of different components. The relationship between the coding tree unit and the coding unit is shown in FIG. 3 .

Example of Cross Component Prediction (CCP): In the latest Versatile Video Coding (VVC) standard, Cross Component Linear Model (CCLM) is used to reduce redundancy between components. Its linear model is obtained by training the original samples of adjacent pixels of the original pixel block of the luminance component of the current coding unit and the reconstructed samples, and the sample information of the adjacent pixels includes the upper phase of the original pixel block of the luminance component of the current coding unit. The original samples and reconstructed samples of the adjacent pixels, the original samples and reconstructed samples of the adjacent pixels on the upper right side of the original pixel block of the luminance component of the current coding unit, and the adjacent pixels on the left of the original pixel block of the luminance component of the current coding unit. The original sample and the reconstructed sample, the original sample and the reconstructed sample of the adjacent pixels on the lower left side of the original pixel block of the luminance component of the current coding unit. FIG. 4 shows an example of the positional relationship between an original pixel block of an 8×8 luminance component and adjacent pixels, and an original predicted pixel block of a 4×4 chrominance component and adjacent pixels under the color format YUV4:2:0, respectively.

In the current coding unit, the prediction samples of the pixels in the prediction block of the chrominance component are obtained from the reconstructed samples of the pixels in the original pixel block of the luminance component of the current coding unit through linear model calculation and down-sampling, where the linear model calculation process represents as follows:

Pred _C (i, j)=α·Rec _L (i, j)+β (1)

Among them, (i, j) is the coordinate of the pixel, i specifically refers to the abscissa of the prediction block of the chrominance component of the current coding unit, the range is [0, width-1], the step size is 1, and the width is the current coding The width of the prediction block of the chrominance component of the unit, which can be 4, 8, 16, and 32; j specifically refers to the ordinate of the prediction block of the chrominance component of the current coding unit, and its range is [0, height- 1], the step size is 1, height is the height of the prediction block of the chrominance component of the current coding unit, and its value can be 4, 8, 16 and 32, Rec _L is the weight of the pixel in the original pixel block of the luminance component. Pred _c is the prediction sample of the pixel in the prediction block of the chrominance component, and α and β are the coefficients of the linear model.

The CCLM technology of VVC includes LM, LM_L and LM_A modes. Among them, LM_L only uses the left adjacent samples to calculate the linear model, and LM_A only uses the upper adjacent samples to calculate the linear model.

In another example of cross-component prediction, the latest cross-component technology proposal M4612 adopted by China's Audio Video coding Standard (AVS) is the Two Step Cross-component Prediction Mode (TSCPM). During the encoding process, as shown in Figure 5A, the intra-coded luminance component calculates up to 65 Intra Prediction modes, where DC represents the mean mode, Plane represents the plane mode, Bilinear represents the bilinear mode, and Zone represents the zone . The optimal result is selected according to the rate distortion (Rate Distortion) cost, and the intra prediction mode and the corresponding prediction residual are transmitted. Intra-coded chrominance components in the current coding unit perform calculation of up to 11 intra-prediction modes of chrominance components, including the calculation of 5 intra-prediction modes of chrominance components with reference to single chrominance component information and the calculation of chrominance component intra-prediction modes with reference to multi-component information. 6 kinds of chrominance component intra-frame prediction modes are calculated, and the above-mentioned intra-frame chrominance prediction mode referring to single chrominance component information is the chrominance component common intra-frame prediction mode.

When using the chroma component normal intra prediction mode on the pixels of the prediction block of the chroma component, the current chroma coding block is based on the available information of the reconstructed samples of the adjacent prediction blocks of the chroma component and the corresponding chroma component frame Intra-prediction mode, computes prediction samples for the current chroma coded block. The reference pixels of adjacent prediction blocks selected by different prediction modes are also inconsistent. Some prediction modes can directly use the reconstructed samples of the pixels of adjacent coding blocks to calculate the prediction samples, while some prediction modes need to reconstruct the pixels of adjacent coding blocks. The constructed samples are interpolated, and then the reference pixels are selected to calculate the predicted samples of the current coding block. Figure 5B shows a schematic diagram of an intra-frame prediction mode with a coding block size of 8×8. (1) in the figure is a normal intra-frame vertical angle-like prediction mode. This mode uses the reference pixels of the adjacent blocks on the upper side to predict the current coding block. Sample calculation, (2) is the normal intra-frame horizontal class angle prediction mode, this mode uses the reference pixel of the adjacent block on the left to calculate the prediction sample of the current coding block, (3) is the normal intra-frame non-angle prediction mode, This mode computes the prediction samples of the current coded block using both the reference pixels of the upper and left adjacent blocks.

When performing cross-component technology prediction on the pixels of the prediction block of the chroma component, the reconstructed samples of the adjacent pixels of the original pixel block of the luma component of the current coding unit and the phase of the original prediction pixel block of the chroma component of the current coding unit The reconstructed samples of neighboring pixels are used for the computation of the linear model. The adjacent pixels of the original pixel block of the luminance component include the upper adjacent pixels and left adjacent pixels of the original pixel block of the luminance component of the current coding unit; the adjacent pixels of the prediction block of the chrominance component include the current The upper neighbor pixel and the left neighbor pixel of the prediction block of the chroma component of the coding unit.

When selecting the reconstructed samples as the reference samples for calculating the coefficients of the linear model, combined with the availability of the reconstructed samples of the adjacent pixels, the reconstructed samples of two pixels in the adjacent pixels on the upper side and the two pixels in the adjacent pixels on the left can be used. For the combination of the reconstructed samples of the pixels, the reconstructed samples of the four pixels in the adjacent pixels on the upper side may be all used, and the reconstruction samples of the four pixels of the adjacent pixels on the left side may be all used.

According to the selection of the above reference samples, the prediction mode includes, if the original pixel block of the luminance component and the original pixel block of the chrominance component corresponding to the current coding unit (for the convenience of description, this end is collectively referred to as the original pixel block) adjacent pixels on the upper side When the reconstructed samples of the current coding unit and the reconstructed samples of the adjacent pixels on the left of the original pixel block of the current coding unit are available, and the coefficient calculation of the linear model adopts the reference samples from both the upper and left adjacent pixels, or if the current For the original pixel block corresponding to the coding unit, only the reconstructed samples of the adjacent pixels on the upper side are available, and the reference samples used in the calculation of the linear model coefficients are only the reconstructed samples of the adjacent pixels on the upper side, or if the original pixel corresponding to the current coding unit is used. When only the reconstructed samples of the adjacent pixels on the left side of the block are available, and the reference samples used in the calculation of the coefficients of the linear model are only the reconstructed samples of the adjacent pixels on the left side, they are all in TSCPM mode; if the original pixel corresponding to the current coding unit The reconstructed samples of the adjacent pixels on the upper side of the block and the reconstructed samples of the adjacent pixels on the left side of the original pixel block corresponding to the current coding unit are available, and the reference samples used in the calculation of the coefficients calculated by the linear model are only selected from the adjacent pixels on the upper side. When the reconstructed sample of the pixel is in TSCPM_T mode; if the reconstructed sample of the adjacent pixel on the upper side of the original pixel block corresponding to the current coding unit and the reconstructed sample of the adjacent pixel on the left side of the original pixel block corresponding to the current coding unit are available , and only the reconstructed samples of the adjacent pixels on the upper side are selected as the reference samples used in the calculation of the coefficients of the linear model, it is the TSCPM_L mode.

In the above-mentioned reference samples used for the calculation of the coefficients of the linear model, as shown in FIG. 6 , if the reference samples are from adjacent pixels on both sides of the original pixel block corresponding to the current coding unit, the upper reference samples are selected from the upper side. The reconstructed sample of the leftmost pixel in the adjacent pixels and the reconstructed sample of the rightmost pixel on the upper side of the width of the original pixel block corresponding to the current coding unit, the left reference sample is selected from the reconstruction of the uppermost pixel among the adjacent pixels on the left The sample is the reconstructed sample of the lowermost pixel in the left adjacent pixel of the height of the original pixel block corresponding to the current coding unit; if the reference sample used for the calculation of the coefficients of the linear model is only from the upper side, the current coding unit is used as the reconstruction sample. The quarter distance of the width of the corresponding original pixel block is the step size, and the reconstructed samples of pixels with four consecutive steps in the adjacent pixels on the upper side are selected; if the reference sample is only from the left side, the current coding unit is used. The quarter distance of the height of the corresponding original pixel block is the step size, and the reconstructed samples of four consecutive step size pixels among the four left adjacent pixels are selected.

That is, the adjacent pixels of the four luminance components and the adjacent pixels of the four chrominance components can be selected in three ways.

Method 1: When two adjacent pixels are selected from the upper adjacent coding block and the left adjacent coding block respectively, the adjacent pixels can be selected by the following formula:

minStep=min(Width,Height);

TopIndex=(minStep-1)*Width/minStep;

LeftIndex=(minStep–1)*Height/minStep;

In the above formula, min(x,y) returns the smaller value of x and y, Width is the width of the chrominance component of the current coding block, Height is the height of the chrominance component of the current coding block, and TopIndex is to select the adjacent upper boundary. The index value of another adjacent pixel except the first adjacent pixel when it is a pixel, and LeftIndex is the index value of another adjacent pixel except the first adjacent pixel when selecting the adjacent pixel on the left border;

Method 2: When only four adjacent pixels are selected from the adjacent coding block on the upper side, starting from the first adjacent pixel on the far left, the step size is a quarter of the width of the chrominance component of the current coding block, Select four adjacent pixels of luminance components and four adjacent pixels of chrominance components;

Method 3: When only four adjacent pixels are selected from the adjacent coding block on the left, starting from the first adjacent pixel on the uppermost side, with a quarter of the height of the chrominance component of the current coding block as the step size, select four adjacent pixels. adjacent pixels of the luminance component and four adjacent pixels of the chrominance component;

In the above-mentioned specific example AVS3, the linear model calculation formula of the cross-component technology is the same as the above-mentioned formula (1), wherein α and β can be calculated by the following formula:

β=Y _Min -α·X _Min (3)

Wherein, Y _Max is the average value of the two largest reconstructed samples in the reconstructed samples of multiple adjacent pixel points of the original pixel block of the chrominance component used for the calculation of the coefficients of the linear model, and Y _Min is the average value of the two largest reconstructed samples used for the linear model The calculated coefficient of the chrominance component is the average of the two smallest reconstructed samples among the reconstructed samples of multiple adjacent pixel points of the original pixel block of the chrominance component. X _Max is the average value of the two largest reconstructed samples among the reconstructed samples of multiple adjacent pixel points of the original pixel block of the luminance component used for the calculation of the coefficients of the linear model, and X _Min is the coefficient used for the linear model The average value of the two smallest reconstructed samples among the reconstructed samples of a plurality of adjacent pixel points of the original pixel block of the calculated luminance component.

Cross-component prediction is performed according to the calculated linear model, and the luminance component reconstruction block of the current CU is used to generate a corresponding chroma component reference prediction block (Chroma Reference Prediction Pixel Block). Specifically, the reference prediction sample of the chrominance component of each pixel of the current coding unit is calculated according to equations (1)/(2) and (3). The size of the chrominance component reference prediction block and the size of the original pixel block of the luminance component are calculated. same. In a specific example, the input digital video color format is generally YUV 4:2:0 format, that is, the size of the chrominance component prediction block is one quarter of the original pixel block of the luma component. In order to obtain the corresponding correct size chrominance component prediction block, the chrominance component reference prediction block needs to downsample the horizontal and vertical directions by half, and the chrominance component prediction block after downsampling is the corresponding luminance. A quarter of the original pixel block of the component, which satisfies the size requirements of the color format constraints. Wherein, the filter used for down-sampling the chrominance component reference prediction block uses a downsampling filter with two taps of the same coefficient in the left border pixel area of the chrominance component reference prediction block, and uses six-sampling filter in other pixel areas. A downsampling filter that taps two different coefficients.

A downsampling filter with six taps and two different coefficients is shown in equation (4).

Wherein, x, y are the coordinates of the pixel, P' _C is the predicted sample of the luminance component of the current pixel, and P ¹ _C and P ² _C are the predicted sample of the chrominance component of the current pixel.

The down-sampling filter with the same coefficient of two taps is shown in equation (5).

Wherein, x, y are the coordinates of the pixel, P' _C is the predicted sample of the luminance component of the current pixel, and P ¹ _C and P ² _C are the predicted sample of the chrominance component of the current pixel.

The downsampling filter is shown in Figure 7, where x1 means multiplying by 1, and x2 means multiplying by 2. Fig. 8 is a schematic diagram showing the change from the luminance component reconstruction block to the chrominance component prediction block in the cross-component technique, wherein the size of the luminance component reconstruction block of the coding unit is 8*8, and the size of the corresponding chrominance component reference prediction block is 8*8, the size of the filtered chrominance component prediction block is 4*4.

AVS3 also adopts a variety of cross-component prediction modes MCPM. The three prediction modes of MCPM are similar to the TSCPM prediction modes. The MCPM mode corresponds to the TSCPM mode, the MCPM_T mode corresponds to the TSCPM_T mode, and the MCPM_L mode corresponds to the TSCPM_L mode. However, the chrominance component prediction process is different. The chrominance U component prediction process of the three prediction modes of MCPM is consistent with the TSCPM mode, while the prediction block of the chroma V component is obtained by subtracting the reconstruction block of the U component from the temporary chroma prediction component block. get. The specific formula is as follows:

Pred _C (x, y)=α′·Rec _L (x, y)+β′ (6)

Pred _Cr (x, y) = Pred _C (x, y) - Rec _Cb (x, y) (7)

In the above equations (2) and (3), Pred _C (x, y) is the prediction sample located at the pixel (x, y) in the prediction block of the chrominance component, and Rec _L (x, y) is the prediction sample located at the luminance component. The reconstructed sample at the pixel (x, y) in the reconstructed block, Pred _C '(x, y) is the predicted sample at the pixel (x, y) in the prediction block of the chrominance component after downsampling, Rec _cb ( x, y) is the reconstructed sample of the U component located at the pixel (x, y) in the reconstructed block of the chrominance component, and Pred _Cr (x, y) is the pixel (x, y) located in the prediction block of the chrominance component. For the prediction samples of the V component, α' and β' are the sum of the linear parameters of the U component and the V component, respectively. For the calculation of the linear parameters of the U component and the V component, refer to equations (2) and (3). At present, the existing enhanced two-step cross-component prediction technology uses all reconstructed samples from the upper or left adjacent coding units as reference information to calculate the linear model to obtain the reference prediction block of the chroma component of the current coding unit. , if only the reconstructed samples from the adjacent pixels on the upper side are taken, there is a lack of reference information for the reconstructed samples from the adjacent pixels on the left; Reference information for reconstructed samples of neighboring pixels.

In the existing chrominance component intra prediction mode, when selecting pixels as reference pixels of the prediction mode, the correlation between some reference pixels and the current coding block is often ignored. The current coding block has spatial correlation with all adjacent pixels. If only the upper adjacent pixels are taken, there is a lack of reference information from the left adjacent pixels; if only the left adjacent pixels are taken, there is a lack of reference information from the left adjacent pixels. The reference information of the adjacent pixels on the upper side.

The existing chrominance component common intra prediction mode selects adjacent pixels in the corresponding direction as reference pixels according to the directionality of the prediction mode, but the current coding block also has a certain correlation with adjacent pixels not in this direction. The prediction effect of only referring to adjacent pixels in a single direction is not good enough, and the reference information of other adjacent pixels is wasted. The existing cross-component chrominance prediction mode selects the upper or left adjacent pixel as the reference pixel to calculate the linear model according to the prediction mode. There are also some problems. If the upper adjacent pixel is selected as the reference pixel, the current encoding is ignored. The spatial correlation between the block and the left coding block; if the left adjacent pixel is selected as the reference pixel, the spatial correlation between the current coding block and the upper coding block is ignored.

In this way, a large amount of available reference information is wasted by the prediction, and the sample value of the chrominance component of the current coding unit cannot be predicted well, and the coding efficiency is lost.

In view of the above-mentioned technical problems, the application proposes the following design ideas:

Prediction correction is performed on the prediction block calculated by the normal intra prediction mode of the chrominance component.

If the current coding block only selects the adjacent pixels of the chrominance components on the upper side as reference pixels to calculate the prediction samples of the current coding block, the adjacent pixels of the chrominance components on the left side are used as reference pixels to predict the samples of the chrominance components of the current coding block. make forecast revisions;

If only the adjacent pixels of the chrominance component on the left side of the current coding block are selected as reference pixels to calculate the prediction samples of the current coding block, the adjacent pixels of the chrominance components on the upper side are used as reference pixels for the prediction samples of the chrominance components of the current coding block. make forecast revisions;

If the current coding block adopts the normal intra-frame non-angle prediction mode of the chrominance component, the adjacent pixels of the chrominance component on the upper side and the left side are used as reference pixels to perform prediction modification on the prediction samples of the chrominance component of the current coding block.

Prediction correction is performed on the prediction samples calculated by the chroma component cross-component prediction mode.

If the current coding block only selects the adjacent pixels of the upper luminance component and the adjacent pixels of the upper chrominance component to calculate the linear model, the adjacent pixels of the left chrominance component are used as reference pixels to predict the chrominance components of the current coding block. make forecast revisions;

If the current coding block only selects the adjacent pixels of the left luminance component and the adjacent pixels of the left chrominance component to calculate the linear model, the adjacent pixels of the upper chrominance component are used as reference pixels to predict the chrominance components of the current coding block. Make forecast corrections.

The above-mentioned prediction correction for the prediction sample of the current coding block includes, according to the distance between the current pixel and the adjacent pixels of the reference as the filter coefficient index value, according to the size of the current coding block as the filter coefficient group index value, according to the filter coefficient group index. The value searches the chroma component intra prediction filter coefficient group and finds the chroma component intra prediction filter coefficient in the group according to the filter coefficient index value, and calculates the modified prediction sample according to the obtained filter coefficient and the prediction correction formula.

Specifically, at the coding end, it is first determined whether the current coding block can use the prediction modification technique of the chrominance component.

If the prediction correction of the chrominance component is used, intra-frame prediction is performed on the luminance component of the current coding block, and the prediction sample correction is performed on the prediction sample after the prediction is completed, and then the intra-frame prediction is performed on the chrominance component of the current coding block, and Prediction correction is performed on the prediction samples after the end of the prediction.

The above-mentioned prediction modification for the current coding block includes prediction modification techniques that need to transmit an identification bit and do not need to transmit an identification bit to indicate whether the current coding block uses a chrominance component.

If the current prediction correction technology needs to transmit the flag bit, it is judged whether to use the prediction correction technology of intra-frame prediction according to the rate-distortion cost calculated by the uncorrected prediction sample and the corrected prediction sample.

If the rate-distortion cost calculated for the uncorrected prediction sample is small, the current coding block does not use the prediction correction technique of intra-frame prediction, and the flag bit is transmitted and indicated as NO;

If the rate-distortion cost calculated for the prediction sample after the prediction modification is small, the current chrominance component coding block uses the prediction modification technique of intra-frame prediction, and the flag bit is transmitted and expressed as true;

If the current prediction modification technology does not need to transmit the flag bit, the prediction modification is directly applied to the prediction samples of the current coding block, and the modified prediction samples are obtained.

Specifically, at the decoding end, first parse and obtain whether the current code stream can use the prediction modification technology of intra-frame prediction of chrominance components.

If a prediction modification technique can be used, the code stream is parsed to obtain the prediction mode of the current chrominance component of the current decoding block, and specific adjacent pixels are selected as reference pixels to perform prediction modification on the prediction samples of the current decoding block.

The above-mentioned process of performing prediction modification on the prediction samples of the current decoding block includes: the current decoding block needs an identification bit to indicate whether the prediction modification technique is used and the unneeded identification bit indicates whether the prediction modification technique is used.

If the current decoding block needs an identification bit to indicate whether to use the prediction modification technology, the code stream of the current decoding block is parsed to obtain the identification bit value and the prediction mode of the chrominance component.

If the value of the flag is true, the prediction sample is calculated according to the prediction mode of the current chrominance component.

If the calculation prediction sample selects the upper adjacent pixel as the reference pixel, then the left adjacent pixel is used as the reference pixel to perform prediction correction on the prediction sample;

If the calculation prediction sample selects the left adjacent pixel as the reference pixel, then the upper adjacent pixel is used as the reference pixel to perform prediction correction on the prediction sample;

If the value of the flag value is no, the predicted sample is calculated according to the prediction mode of the current chrominance component, and the predicted sample is not filtered;

If the current decoding block does not need the flag to indicate whether to use the prediction modification technique, the code stream of the current decoding block is parsed to obtain the prediction mode of the chrominance component, and the prediction sample is calculated according to the prediction mode of the current chrominance component.

If the calculation decoding block selects the adjacent pixel on the upper side as the reference pixel, then the adjacent pixel on the left side is used as the reference pixel to perform prediction correction on the prediction sample;

If the calculation decoding block selects the adjacent pixels on the left side as reference pixels, the adjacent pixels on the upper side are used as reference pixels to perform prediction correction on the predicted samples.

In the embodiments of the present application, the spatial correlation between adjacent coding blocks and the current coding block is used to correct the prediction samples of the chrominance components of the current coding block, so as to improve the prediction accuracy and coding efficiency.

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

FIG. 9 is a block diagram of an example video coding system 1 described in the embodiments of the present application. As used herein, the term "video coder" generally refers to both a video encoder and a video decoder. In this application, the term "video coding" or "coding" may generally refer to video encoding or video decoding. The video encoder 100 and the video decoder 200 of the video coding system 1 are used to implement the cross-component prediction method proposed in this application.

As shown in FIG. 9 , video coding system 1 includes source device 10 and destination device 20 . Source device 10 produces encoded video data. Accordingly, source device 10 may be referred to as a video encoding device. Destination device 20 may decode the encoded video data generated by source device 10 . Accordingly, destination device 20 may be referred to as a video decoding device. Various implementations of source device 10, destination device 20, or both may include one or more processors and a memory coupled to the one or more processors. The memory may include, but is not limited to, RAM, ROM, EEPROM, flash memory, or any other medium that may be used to store the desired program code in the form of instructions or data structures accessible by a computer, as described herein.

Source device 10 and destination device 20 may include various devices including desktop computers, mobile computing devices, notebook (eg, laptop) computers, tablet computers, set-top boxes, telephone handsets such as so-called "smart" phones, etc. , televisions, cameras, display devices, digital media players, video game consoles, in-vehicle computers, or the like.

Destination device 20 may receive encoded video data from source device 10 via link 30 . Link 30 may include one or more media or devices capable of moving encoded video data from source device 10 to destination device 20 . In one example, link 30 may include one or more communication media that enable source device 10 to transmit encoded video data directly to destination device 20 in real-time. In this example, source device 10 may modulate the encoded video data according to a communication standard, such as a wireless communication protocol, and may transmit the modulated video data to destination device 20 . The one or more communication media may include wireless and/or wired communication media, such as radio frequency (RF) spectrum or one or more physical transmission lines. The one or more communication media may form part of a packet-based network, such as a local area network, a wide area network, or a global network (eg, the Internet). The one or more communication media may include routers, switches, base stations, or other equipment that facilitates communication from source device 10 to destination device 20 . In another example, the encoded data may be output from output interface 140 to storage device 40 .

The image encoding and decoding techniques of the present application can be applied to video encoding and decoding to support a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, streaming video transmission (eg, via the Internet), for storage in data storage Encoding of video data on media, decoding of video data stored on data storage media, or other applications. In some examples, video coding system 1 may be used to support one-way or two-way video transmission to support applications such as video streaming, video playback, video broadcasting, and/or video telephony.

The video coding system 1 illustrated in FIG. 9 is merely an example, and the techniques of this application may be applicable to video coding setups (eg, video encoding or video decoding) that do not necessarily include any communication of data between an encoding device and a decoding device. . In other instances, data is retrieved from local storage, streamed over a network, and the like. A video encoding device may encode and store data to memory, and/or a video decoding device may retrieve and decode data from memory. In many instances, encoding and decoding is performed by devices that do not communicate with each other, but merely encode data to and/or retrieve data from memory and decode data.

In the example of FIG. 9 , source device 10 includes video source 120 , video encoder 100 , and output interface 140 . In some examples, output interface 140 may include a modulator/demodulator (modem) and/or a transmitter. Video source 120 may include a video capture device (eg, a video camera), a video archive containing previously captured video data, a video feed interface to receive video data from a video content provider, and/or a computer to generate video data A graphics system, or a combination of such sources of video data.

Video encoder 100 may encode video data from video source 120 . In some examples, source device 10 transmits the encoded video data directly to destination device 20 via output interface 140 . In other examples, the encoded video data may also be stored on storage device 40 for later access by destination device 20 for decoding and/or playback.

In the example of FIG. 9 , destination device 20 includes input interface 240 , video decoder 200 , and display device 220 . In some examples, input interface 240 includes a receiver and/or a modem. Input interface 240 may receive encoded video data via link 30 and/or from storage device 40 . The display device 220 may be integrated with the destination device 20 or may be external to the destination device 20 . Generally, display device 220 displays decoded video data. The display device 220 may include various display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or other types of display devices.

Although not shown in Figure 9, in some aspects video encoder 100 and video decoder 200 may each be integrated with an audio encoder and decoder, and may include appropriate multiplexer-demultiplexer units or other hardware and software to handle the encoding of both audio and video in a common data stream or separate data streams.

Video encoder 100 and video decoder 200 may each be implemented as any of a variety of circuits such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), Field Programmable Gate Array (FPGA), discrete logic, hardware, or any combination thereof. If the application is implemented in part in software, a device may store instructions for the software in a suitable non-volatile computer-readable storage medium, and the instructions may be executed in hardware using one or more processors Thus, the technology of the present application is implemented. Any of the foregoing (including hardware, software, a combination of hardware and software, etc.) may be considered one or more processors. Each of video encoder 100 and video decoder 200 may be included in one or more encoders or decoders, either of which may be integrated as a combined encoder in the respective device /decoder (codec) part.

FIG. 10 is an exemplary block diagram of a video encoder 100 described in the embodiments of the present application. The video encoder 100 is used to output the video to the post-processing entity 41 . Post-processing entity 41 represents an example of a video entity that can process encoded video data from video encoder 100, such as a Media Aware Network Element (MANE) or a splicing/editing device. In some cases, post-processing entity 41 may be an instance of a network entity. In some video encoding systems, post-processing entity 41 and video encoder 100 may be parts of separate devices, while in other cases, the functionality described with respect to post-processing entity 41 may be performed by the same device that includes video encoder 100 implement. In an example, post-processing entity 41 is an example of storage device 40 of FIG. 1 .

In the example of FIG. 10 , video encoder 100 includes prediction processing unit 108 , filter unit 106 , memory 107 , summer 112 , transformer 101 , quantizer 102 , and entropy encoder 103 . The prediction processing unit 108 includes an inter predictor 110 and an intra predictor 109 . For image block reconstruction, the video encoder 100 also includes an inverse quantizer 104 , an inverse transformer 105 and a summer 111 . Filter unit 106 represents one or more loop filters, such as deblocking filters, adaptive loop filters (ALF), and sample adaptive offset (SAO) filters. Although the filter unit 106 is shown in FIG. 10 as an in-loop filter, in other implementations the filter unit 106 may be implemented as a post-loop filter. In an example, the video encoder 100 may further include a video data memory and a division unit (not shown in the figure).

The video encoder 100 receives video data and stores the video data in a video data memory. The division unit divides the video data into several image blocks, and these image blocks can be further divided into smaller blocks, such as image block division based on a quad-tree structure or a binary tree structure. Prediction processing unit 108 may select one of a plurality of possible coding modes for the current image block, such as one of a plurality of intra-coding modes or one of a plurality of inter-coding modes. Prediction processing unit 108 may provide the resulting intra-, inter-coded block to summer 112 to generate a residual block, and to summer 111 to reconstruct the encoded block for use as a reference image. Intra-predictor 109 within prediction processing unit 108 may perform intra-predictive encoding of the current image block relative to one or more neighboring blocks in the same frame or slice as the current block to be encoded to remove spatial redundancy . Inter predictor 110 within prediction processing unit 108 may perform inter-predictive encoding of the current image block relative to one or more prediction blocks in one or more reference images to remove temporal redundancy. Prediction processing unit 108 provides information indicative of the selected intra or inter prediction mode for the current image block to entropy encoder 103 so that entropy encoder 103 encodes the information indicative of the selected inter prediction mode.

After prediction processing unit 108 generates a prediction block for the current image block via inter prediction/intra prediction, video encoder 100 forms a residual image block by subtracting the prediction block from the current image block to be encoded. Summer 112 represents one or more components that perform this subtraction operation. Residual video data in the residual block may be included in one or more TUs and applied to transformer 101 . Transformer 101 transforms the residual video data into residual transform coefficients using a transform such as a discrete cosine transform (DCT) or a conceptually similar transform. Transformer 101 may convert residual video data from a pixel value domain to a transform domain, such as a frequency domain.

Transformer 101 may send the resulting transform coefficients to quantizer 102 . Quantizer 102 quantizes the transform coefficients to further reduce the bit rate. In some examples, quantizer 102 may then perform a scan of the matrix including the quantized transform coefficients. Alternatively, the entropy encoder 103 may perform scanning.

After quantization, the entropy encoder 103 entropy encodes the quantized transform coefficients. For example, the entropy encoder 103 may perform context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), syntax-based context adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) ) encoding or another entropy encoding method or technique. After entropy encoding by entropy encoder 103 , the encoded codestream may be transmitted to video decoder 200 , or archived for later transmission or retrieval by video decoder 200 . The entropy encoder 103 may also entropy encode the syntax elements of the current image block to be encoded.

Inverse quantizer 104 and inverse transformer 105 apply inverse quantization and inverse transform, respectively, to reconstruct the residual block in the pixel domain, eg, for later use as a reference block for a reference image. Summer 111 adds the reconstructed residual block to the prediction block produced by inter predictor 110 or intra predictor 109 to produce a reconstructed image block. Filter unit 106 may be applied to reconstructed image blocks to reduce distortions, such as block artifacts. This reconstructed image block is then stored in memory 107 as a reference block, which can be used as a reference block by inter-predictor 110 to inter-predict blocks in subsequent video frames or images.

Specifically, the video encoder 100 specifically implements the image encoding method provided by the embodiment of the present application, the input video is divided into several coding tree units, and each coding tree unit is further divided into several rectangular or square coding units. When the current coding unit selects the intra-frame prediction mode for coding, perform calculation traversal of several prediction modes on the luminance component of the current coding unit, select the optimal prediction mode according to the rate-distortion cost, and perform several prediction modes on the chrominance component of the current coding unit. The calculation of the prediction mode goes through and selects the optimal prediction mode according to the rate-distortion cost. After that, the residual between the original video block and the predicted block is calculated. The residual is subsequently transformed, quantized, and entropy encoded to form an output stream, and the other is subjected to inverse transformation, inverse quantization, and loop filtering to form a reconstructed sample. As reference information for subsequent video compression.

The intra predictor 109 may also provide information indicating the selected intra prediction mode for the current coding unit to the entropy encoder 103 so that the entropy encoder 103 encodes the information indicating the selected intra prediction mode.

FIG. 11 is an exemplary block diagram of a video decoder 200 described in the embodiments of the present application. In the example of FIG. 11 , video decoder 200 includes entropy decoder 203 , prediction processing unit 208 , inverse quantizer 204 , inverse transformer 205 , summer 211 , filter unit 206 , and memory 207 . Prediction processing unit 208 may include inter predictor 210 and intra predictor 209 . In some examples, video decoder 200 may perform a decoding process that is substantially the reciprocal of the encoding process described with respect to video encoder 100 from FIG. 10 .

During the decoding process, video decoder 200 receives from video encoder 100 an encoded video codestream representing image blocks of an encoded video slice and associated syntax elements. The video decoder 200 may receive video data from the network entity 42, and optionally, may also store the video data in a video data storage (not shown in the figure). Video data memory may store video data to be decoded by components of video decoder 200, such as an encoded video codestream. The video data stored in the video data store may be obtained, for example, from the storage device 40, from a local video source such as a camera, via wired or wireless network communication of the video data, or by accessing a physical data storage medium. The video data memory may serve as a decoded picture buffer (CPB) for storing encoded video data from the encoded video codestream.

Network entity 42 may be, for example, a server, a MANE, a video editor/splicer, or other such device for implementing one or more of the techniques described above. Network entity 42 may or may not include a video encoder, such as video encoder 100 . Network entity 42 may implement portions of the techniques described in this application before network entity 42 sends the encoded video stream to video decoder 200 . In some video decoding systems, network entity 42 and video decoder 200 may be part of separate devices, while in other cases, functionality described with respect to network entity 42 may be performed by the same device that includes video decoder 200 .

Entropy decoder 203 of video decoder 200 entropy decodes the codestream to generate quantized coefficients and some syntax elements. Entropy decoder 203 forwards the syntax elements to prediction processing unit 208 . Video decoder 200 may receive syntax elements at the video slice level and/or the tile level. When a video slice is decoded as an intra-decoded (I) slice, the intra-predictor 209 of the prediction processing unit 208 is based on the signaled intra-prediction mode and data from previously decoded blocks of the current frame or picture Instead, the prediction block of the image block of the current video slice is generated. When a video slice is decoded as an inter-decoded (ie, B or P) slice, inter predictor 210 of prediction processing unit 208 may determine, based on syntax elements received from entropy decoder 203, which method to use for the current The inter prediction mode in which the current image block of the video slice is decoded, based on the determined inter prediction mode, the current image block is decoded (eg, inter prediction is performed).

The inverse quantizer 204 inversely quantizes, ie dequantizes, the quantized transform coefficients provided in the codestream and decoded by the entropy decoder 203 . The inverse quantization process may include using the quantization parameters calculated by the video encoder 100 for each image block in the video slice to determine the degree of quantization that should be applied and, likewise, the degree of inverse quantization that should be applied. The inverse transformer 205 applies an inverse transform to the transform coefficients, such as an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to produce a residual block in the pixel domain.

After the inter predictor 210 generates a prediction block for the current image block or a sub-block of the current image block, the video decoder 200 performs the prediction by comparing the residual block from the inverse transformer 205 with the corresponding prediction generated by the inter predictor 210 The blocks are summed to obtain a reconstructed block, a decoded image block. Summer 211 represents the component that performs this summation operation. Loop filters may also be used (in the decoding loop or after the decoding loop) to smooth pixel transitions or otherwise improve video quality, if desired. Filter unit 206 may represent one or more loop filters, such as deblocking filters, adaptive loop filters (ALF), and sample adaptive offset (SAO) filters. Although filter unit 206 is shown in FIG. 11 as an in-loop filter, in other implementations filter unit 206 may be implemented as a post-loop filter.

The image decoding method specifically executed by the video decoder 200 includes: after parsing, inverse transformation and inverse quantization of the input code stream, the prediction mode index of the current coding unit is obtained.

If the prediction mode index of the chroma component of the current coding unit is the enhanced two-step cross-component prediction mode, select only the reconstructed samples from the upper or left adjacent pixels of the current coding unit according to the index value to calculate the linear model , calculate the reference prediction block of the chrominance component of the current coding unit according to the linear model, downsample, and perform prediction correction based on the correlation of the adjacent pixels of the border in the orthogonal direction for the downsampled prediction block to obtain the final color The final prediction block for the degree component.

One channel of the subsequent code stream is used as reference information for subsequent video decoding, and the other channel is post-filtered to output the video signal.

It should be understood that other structural variations of video decoder 200 may be used to decode encoded video codestreams. For example, video decoder 200 may generate an output video stream without being processed by filter unit 206; or, for some image blocks or image frames, entropy decoder 203 of video decoder 200 does not decode quantized coefficients, and accordingly Processing by inverse quantizer 204 and inverse transformer 205 is not required.

Specifically, the intra-frame predictor 209 may use the image decoding method described in the embodiments of the present application in the process of generating the prediction block.

FIG. 12A is a schematic flowchart of an image encoding method in an embodiment of the present application. The image encoding method may be applied to the source device 10 in the video decoding system 1 shown in FIG. 9 or the video encoder 100 shown in FIG. 10 . The flow shown in FIG. 12A is described by taking the execution subject as the video encoder 100 shown in FIG. 10 as an example. As shown in FIG. 12A , the cross-component prediction method provided by the embodiment of the present application includes:

Step 110: Divide the image to determine the intra prediction mode of the chrominance component of the current coding block.

The color format of the video to which the image belongs includes, but is not limited to, 4:2:0, 4:2:2, and the like.

For example, when the color format is 4:2:0, as shown in (c) of Figure 2, the pixel ratio of the original pixel block of the luminance component to the original pixel block of the chrominance component of the current coding block is 4:1, Taking an 8*8 positive square pixel array as an example, the size of the original pixel block of the corresponding luminance component is 8*8, and the size of the original pixel block of the corresponding chrominance component is 4*4.

For another example, when the color format is 4:2:2, as shown in (b) in FIG. 2 , the pixel ratio of the original pixel block of the luminance component and the original pixel block of the chrominance component of the current coding block is 2:1 , taking an 8*8 positive square pixel array as an example, the size of the original pixel block of the corresponding luminance component is 8*8, and the size of the original pixel block of the corresponding chrominance component is 8*4.

Among them, the chrominance component intra prediction mode performs calculation of up to 11 chrominance component intra prediction modes, including the calculation of 5 chrominance component intra prediction modes referring to single chrominance component information and the reference to multi-component information. The intra-frame prediction mode of various chrominance components is calculated, and the above-mentioned intra-frame chrominance prediction mode referring to a single chrominance component information is the normal intra-frame prediction mode of the chrominance component.

Step 120: Determine the prediction block of the chrominance component of the current coding block according to the intra prediction mode of the chrominance component.

In this possible example, the determining, according to the chrominance component intra prediction mode, the prediction block of the chrominance component of the current coding block includes: according to reconstructed samples of adjacent pixels of the current coding block The available information of the chrominance component and the intra prediction mode of the chrominance component are determined, and a reference pixel is determined; the prediction block of the chrominance component of the current coding block is determined according to the reference pixel.

In the specific implementation, for the case where the intra prediction mode of the chrominance component adopts the common intra prediction mode, the prediction block of the chrominance component can be determined in the manner agreed in the protocol. It is not repeated here.

In this possible example, the determining, according to the chrominance component intra prediction mode, the prediction block of the chrominance component of the current coding block includes: determining the luminance component intra prediction mode of the current coding block; When the chrominance component intra prediction mode indicates that the predicted value of the chrominance component of the current coding block is determined using the luminance component of the current coding block, the current coding is determined according to the luminance component intra prediction mode The prediction block for the chroma components of the block.

Among them, as shown in FIG. 5A , the intra-coded luminance component calculates up to 65 intra-frame prediction modes. In the specific implementation, the luminance component calculates up to 62 angular prediction modes and 3 non-angle prediction modes, and selects an optimal one. Intra prediction mode for transmission. The intra prediction mode of the luminance component of the current coding block is a prediction mode with the best rate distortion cost among multiple intra prediction modes, and the multiple intra prediction modes are the intra prediction modes of the luminance component of the current coding block. Intra prediction mode used for prediction.

In this possible example, the determining the prediction block of the chrominance component of the current coding block according to the luminance component intra prediction mode includes: determining the current coding according to the luminance component intra prediction mode the reference prediction block of the chrominance component of the block; filtering the reference prediction block of the chrominance component of the current coding block to obtain the prediction block of the chrominance component of the current coding block.

In a specific implementation, the device may determine that the chrominance component intra prediction mode indicates that the luminance component of the current coding block is used to determine the The predicted value of the chrominance component of the current coded block. The preset intra prediction mode is a luminance component intra prediction mode in a preset direction, and the preset direction includes but is not limited to the horizontal direction (for example: the direction along the X axis in the two-dimensional rectangular coordinate system XoY as shown in FIG. 1 ) ), the vertical direction (for example: the negative direction along the Y axis in the two-dimensional rectangular coordinate system XoY as shown in Figure 1).

In this possible example, the filtering the reference prediction block of the chroma component of the current coding block includes: using a third filter to filter the reference prediction block of the chroma component of the current coding block.

In this possible example, the third filter includes a filter for filtering the left boundary pixel area of the reference prediction block for the chrominance component and a reference prediction block for the chrominance component The filter that filters the non-left boundary pixel area.

In this possible example, the filter for filtering the left boundary pixel region of the reference prediction block of the chrominance component includes a third two-tap filter; the third two-tap filter includes:

P _C (x, y)=(P' _C (2x, 2y)+P' _C (2x, 2y+1)+1)>>1

Wherein, x, _y are the coordinates of the pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast samples.

In this possible example, the filter for filtering the non-left boundary pixel region of the reference prediction block of the chrominance component includes a first six-tap filter; the first six-tap filter includes :

Wherein, x, y are the coordinates of the current pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, _Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast sample.

In this possible example, the determining the reference prediction block of the chrominance component of the current coding block according to the luminance component intra prediction mode includes: determining the current coding block according to the luminance component intra prediction mode A reconstructed block of the luminance component of the coding block; and determining a reference prediction block of the chrominance component of the current coding block according to the reconstructed block of the luminance component of the current coding block.

The size of the reference prediction block of the chrominance component is the same as the size of the reconstructed block of the luminance component. For example, as shown in FIG. 8 , the reconstructed block of the luminance component and the reference prediction block of the chrominance component in the prediction process are both 8*8 pixel arrays.

In this possible example, the determining, according to the reconstructed block of the luminance component of the current coding block, the reference prediction block of the chrominance component of the current coding block includes: determining to use the luminance component of the current coding block A linear model for performing cross-component prediction on the reconstructed block; calculating the reconstructed block of the luminance component according to the linear model to obtain a reference prediction block of the chrominance component of the current coding block.

Wherein, the linear model may be, for example, the linear model of the aforementioned formulas (1) or (2) and (3).

In this possible example, the determining a linear model for performing cross-component prediction using the reconstructed block of the luminance component of the current coding block includes: determining a reference pixel for calculating the linear model, the reference pixel including at least one adjacent pixel of the current coding block; calculating the linear model from the reference pixel.

The selection of the reference pixels for calculating the linear model may be extended to adjacent pixels on the lower left side, the left side, the upper left side, the upper side and the upper right side of the current coding block.

Optionally, if the current encoding block is a partial image block in the current encoding block, the device may select a linear model adapted to the current encoding block from multiple linear models, and specifically may select an appropriate image block for the current encoding block according to image characteristics. Since the coefficient of the linear model has not yet been determined, it needs to be calculated according to the reference pixels. It can be seen that the device can provide a more refined prediction mechanism relative to the encoding block for the chrominance component prediction of the current encoding block, and achieve more refined image prediction.

In this possible example, the determining a reference pixel for calculating the linear model includes: according to available information of reconstructed samples of adjacent pixels of the current coding block and the chrominance component intra prediction mode , determine the reference pixels used to calculate the linear model.

Wherein, the chrominance component intra prediction mode of the current coding block includes any one of TSCPM_T, TSCPM_L, MCPM_T, and MCPM_L. The available information specifically includes available on both sides and available on one side (for example: available on the left side and available on the right side). A detailed description will be given below.

If the intra prediction mode of the chroma component of the current coding block is TSCPM_T or MCPM_T, and the reconstructed samples of the adjacent pixels on the upper side of the original pixel block corresponding to the current coding block are adjacent to the left side of the original pixel block corresponding to the current coding block If the reconstructed samples of the pixels are available, the reference adjacent pixels used to calculate the coefficients of the linear model are 4 of the upper adjacent pixels of the original pixel block, as shown in (b) of FIG. 6 .

If the intra prediction mode of the chroma component of the current coding block is TSCPM_L or MCPM_L, and the reconstructed samples of the adjacent pixels on the upper side of the original pixel block corresponding to the current coding block are adjacent to the left side of the original pixel block corresponding to the current coding block If the reconstructed samples of the pixels are available, the reference adjacent pixels used to calculate the coefficients of the linear model are 4 of the adjacent pixels on the side of the original pixel block, as shown in (c) in FIG. 6 .

It can be seen that in this example, the reference adjacent pixels used for calculating the coefficients of the linear model can be flexibly set according to the availability of reconstructed samples of adjacent pixels and the intra prediction mode of the chrominance component.

In this possible example, the determining a reference pixel for calculating the linear model includes: determining a luminance component intra prediction mode with an optimal rate-distortion cost of adjacent encoding blocks of the current encoding block, determining Reference pixels for computing the linear model.

The intra-frame prediction mode with the optimal rate-distortion cost of the luminance component of the adjacent coding block may be the same as or different from the intra-frame prediction mode with the optimal rate-distortion cost of the luminance component of the current coding block.

Step 130: Perform prediction modification on the prediction block of the chrominance component of the current coding block to obtain the modified prediction block of the chrominance component of the current coding block.

In this possible example, the performing prediction modification on the prediction block of the chrominance component of the current coding block includes: determining a filter according to the intra prediction mode of the chrominance component; The prediction block of the chrominance component of the current coding block performs prediction correction.

In this possible example, the determining the filter according to the chrominance component intra prediction mode includes: when the chrominance component intra prediction mode is TSCPM_T or MCPM_T or a normal intra vertical class angle prediction mode, The filter is set as the first filter.

In this possible example, the first filter is configured to perform the filtering of a pixel region adjacent to the left border of the prediction block of the chroma component of the current coding block and the prediction block of the chroma component of the current coding block The pixel area of is filtered.

In this possible example, the first filter includes a first two-tap filter; the first two-tap filter includes:

P'(x,y)=f(x)·P(-1,y)+(1-f(x))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the coding block, P(-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

For example, in a 4*4 pixel array as shown in FIG. 12B, taking the pixels in the prediction block of the chrominance component and the adjacent pixels on the left side as an example, first, for pixel a and the adjacent pixel 1 on the left side Downsampling using the first two-tap filter to form pixel A of the modified prediction block for the chrominance components, horizontally, downsampling using the first two-tap filter for pixel b and the left border neighbor pixel 1 Pixel B forming the modified prediction block for the chrominance components, and so on for the other columns, until downsampling using the first two-tap filter for pixel p and the left border adjacent pixel 4 forms the modified chrominance component. Pixel P of the prediction block.

In this possible example, the horizontal filter coefficients are determined by a first set of parameters, and the first set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(-1, y) the distance between.

The value of the above-mentioned horizontal filter coefficient is related to the size of the chrominance component of the current coding block and the distance between the predicted pixel and the left adjacent pixel in the prediction block of the current chrominance component.

Specifically, the selection of the above filter coefficients is related to the size of the chrominance component, and is divided into different filter coefficient groups according to the size of the prediction block of the chrominance component of the current coding block, and is selected according to the size of the prediction block of the current chrominance component. The corresponding set of filter coefficients. The selection of the above-mentioned horizontal filter coefficients is related to the distance from the predicted pixel to the adjacent pixel on the left. The distance from the currently predicted pixel to the adjacent pixel on the left is used as the index value, and the corresponding filter coefficient is selected from the corresponding filter coefficient group. . The intra-frame chrominance prediction filter coefficients are specifically shown in Table 1. It is worth noting that all coefficients in the table can be enlarged and shifted in the specific encoding process to reduce computational complexity.

Table 1 Intra-frame chroma prediction filter coefficients

In addition, the filter coefficients of this technology can use a coefficient truncation method to reduce coefficient storage, that is, the filter coefficients of all pixels whose distance from the currently predicted pixel to the left adjacent pixel is greater than 10 are consistent.

In this possible example, the determining the filter according to the chrominance component intra prediction mode includes: when the chrominance component intra prediction mode is TSCPM_L or MCPM_L or a normal intra horizontal angle prediction mode, The filter is set as a second filter.

In this possible example, the second filter is used to perform the filtering of the pixel region adjacent to the upper boundary of the prediction block of the chrominance component of the current coding block and the prediction block of the chrominance component of the current coding block The pixel area of is filtered.

In this possible example, the second filter includes a second two-tap filter; the second two-tap filter includes:

P'(x,y)=f(y)·P(x,-1)+(1-f(y))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chrominance component of the coding block, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

For example, in a 4*4 pixel array as shown in FIG. 12C, taking the pixel in the prediction block of the chrominance component and the upper boundary adjacent pixel as an example, first, for pixel a and the upper boundary adjacent pixel 1 Downsampling using a second two-tap filter to form pixel A of the modified prediction block for the chrominance components, downsampling in the vertical direction using a second two-tap filter for pixel e and upper border neighbor pixel 1 Pixel E of the modified prediction block forming the chrominance component, and so on for the other columns, until downsampling using a second two-tap filter for pixel p and the upper border adjacent pixel 4 forms the modified chrominance component. Pixel P of the prediction block.

In this possible example, the vertical filter coefficients are determined by a second set of parameters, the second set of parameters including the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(x, − 1) the distance between.

Wherein, the value of the vertical filter coefficient is related to the size of the chrominance component of the current coding block and the distance between the predicted pixel and the left adjacent pixel in the prediction block of the current chrominance component.

Specifically, the selection of the above filter coefficients is related to the size of the chrominance component, and is divided into different filter coefficient groups according to the size of the prediction block of the chrominance component of the current coding block, and is selected according to the size of the prediction block of the current chrominance component. The corresponding set of filter coefficients. The selection of the above-mentioned vertical filter coefficients is related to the distance from the predicted pixel to the adjacent pixel on the upper side, and the distance from the currently predicted pixel to the adjacent pixel on the upper side is used as the index value, and the corresponding filter coefficient is selected from the corresponding filter coefficient group. . The intra-frame chrominance prediction filter coefficients are specifically shown in Table 1.

In this possible example, the determining the filter according to the chrominance component intra prediction mode includes: when the chrominance component intra prediction mode is a normal intra non-angular prediction mode, setting the filter to is the third filter.

In this possible example, the third filter is used for predicting the pixel region adjacent to the left boundary of the prediction block of the chroma component of the current coding block and the chroma component of the current coding block The pixel area adjacent to the upper boundary of the block and the pixel area of the prediction block of the chrominance component of the current coding block are filtered.

In this possible example, the third filter includes a first three-tap filter; the first three-tap filter includes:

P'(x, y)=f(x)·P(-1,y)+f(y)·P(x,-1)+(1-f(x)-f(y))·P( x, y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the coding block, P(-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left boundary, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) of the pixel (x, y), f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

For example, in a 4*4 pixel array as shown in FIG. 12D, taking the pixels in the prediction block of chrominance components and the adjacent pixels on the upper side and the adjacent pixels on the left side as an example, first, for pixels a and The upper boundary adjacent pixel 1 and the left adjacent pixel 5 are downsampled using the first three-tap filter to form pixel A of the corrected prediction block for the chrominance components, vertically, for pixel e, upper boundary Neighboring pixel 1 and neighboring pixel 6 on the left border are downsampled using the first three-tap filter to form pixel E of the modified prediction block for the chrominance components, and so on for other columns, until pixel p, the upper border The adjacent pixels 4 and 8 adjacent to the left border are down-sampled using the first three-tap filter to form the pixels P of the modified prediction block of chrominance components.

In this possible example, the horizontal filter coefficients are determined by a first set of parameters, and the first set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(-1, y) the distance between;

The vertical filter coefficients are determined by a second set of parameters including the size of the prediction block of the chrominance components and the distance between pixel (x,y) and pixel P(x,-1).

The values of the vertical filter coefficients and the horizontal filter coefficients are related to the size of the chrominance component of the current coding block and the distance between the predicted pixel and the left adjacent pixel in the prediction block of the current chrominance component.

Specifically, the selection of the above filter coefficients is related to the size of the chrominance component, and is divided into different filter coefficient groups according to the size of the prediction block of the chrominance component of the current coding block, and is selected according to the size of the prediction block of the current chrominance component. The corresponding set of filter coefficients. The selection of the above-mentioned vertical filter coefficients is related to the distance from the predicted pixel to the adjacent pixel on the upper side, and the distance from the currently predicted pixel to the adjacent pixel on the upper side is used as the index value, and the corresponding filter coefficient is selected from the corresponding filter coefficient group. . The intra-frame chrominance prediction filter coefficients are specifically shown in Table 1.

In addition, the filter coefficients of this technology can use a coefficient truncation method to reduce coefficient storage, that is, the filter coefficients of all pixels whose distances from the currently predicted pixel to the upper adjacent pixel are greater than 10 are consistent.

In the specific implementation, after the corrected prediction block of the chrominance component of the current coding block is determined, the device may further calculate the reconstructed block of the chrominance component, and determine the current coding according to the reconstructed block of the chrominance component and the reconstructed block of the luminance component The reconstructed image block of the block.

It can be seen that, in the embodiment of the present application, compared with the prior art, the solution of the present application uses the spatial correlation between the adjacent coding block and the current coding block to correct the prediction samples of the chrominance components of the current coding block, so as to improve the prediction accuracy and coding efficiency .

In a possible example, the performing prediction modification on the prediction block of the chrominance component of the current coding block includes: calculating a first rate-distortion cost of the current coding block without modification, and calculating the a second rate-distortion cost in the corrected case of the current coding block; determining that the first rate-distortion cost is greater than the second rate-distortion cost; performing prediction modification on the prediction block of the chrominance component of the current coding block.

It can be seen that in this example, the number of rate-distortion cost calculations is not increased, and additional rate-distortion cost calculations are not required, thereby avoiding a large increase in computational complexity.

In a possible example, the performing prediction modification on the prediction block of the chrominance component of the current coding block includes: calculating a first rate-distortion cost of the current coding block without modification, and calculating the The second rate-distortion cost of the current coding block under the corrected condition; it is determined that the first rate-distortion cost is greater than the second rate-distortion cost, and the chrominance correction flag is set to a first value, and the first value is used for Indicates that the prediction modification needs to be performed; and performs prediction modification on the prediction block of the chrominance component of the current coding block.

In this possible example, the method further includes: determining that the first rate-distortion cost is less than or equal to the second rate-distortion cost, and setting the chrominance correction flag to a second value, the second value Used to indicate that the prediction correction is not required.

In a specific implementation, the chrominance correction identification bit may be a single or multiple bits. For example, in a single bit, the first value may be 1, and the second value may be 0, which is not uniquely limited herein.

In this possible example, the chrominance correction flag is shared with the luminance correction flag.

In this possible example, the chrominance correction flags are used independently.

In a possible example, the above-mentioned linear model applicable to the current coding block may be replaced by a line-by-line applicable linear model.

In a possible example, the identification bit representation in the existing protocol is added to: each chrominance component uses an identification bit to indicate whether the prediction correction technology is used.

In one possible example, the prediction modification techniques of the present application for chroma components may be used only for individual ones of the chroma component prediction modes.

In a possible example, whether to cancel in advance or directly use the prediction modification technique may be determined according to the prediction modification technique usage information of the adjacent blocks of the current coding block.

Corresponding to the image encoding method described in FIG. 12A , FIG. 13 is a schematic flowchart of the image encoding method in the embodiment of the application, and the image encoding method can be applied to the target device in the video decoding system 1 shown in FIG. 9 . 20 or the video decoder 200 shown in FIG. 11 . The flow shown in FIG. 13 is described by taking the execution subject as the video encoder 200 shown in FIG. 11 as an example. As shown in FIG. 13 , the cross-component prediction method provided by the embodiment of the present application includes:

Step 210: Parse the code stream to determine the intra prediction mode of the chrominance component of the current decoding block.

Wherein, the color format of the video of the code stream includes but is not limited to 4:2:0, 4:2:2, and the like.

In a specific implementation, a syntax element can be obtained from the code stream through entropy decoding, and the syntax element is used to determine a luma component intra prediction mode and a chroma component intra prediction mode for predicting the current decoding block. The luminance component intra prediction mode is an optimal luminance component intra prediction mode among the multiple intra prediction modes, and the multiple intra prediction modes are intra prediction modes used for the luminance component intra prediction.

Step 220, according to the chrominance component intra prediction mode, determine the prediction block of the chrominance component of the current decoding block;

In this possible example, the determining, according to the chrominance component intra prediction mode, the prediction block of the chrominance component of the current decoding block includes: according to reconstructed samples of adjacent pixels of the current decoding block The available information of the chrominance component and the intra prediction mode of the chrominance component are determined, and a reference pixel is determined; the prediction block of the chrominance component of the current decoding block is determined according to the reference pixel.

In this possible example, the determining, according to the chrominance component intra prediction mode, the prediction block of the chrominance component of the current decoding block includes: determining the luma component intra prediction mode of the current decoding block; When the chrominance component intra prediction mode indicates that the predicted value of the chrominance component of the current decoding block is determined using the reconstructed block of the luma component of the current decoding block, according to the luma component intra prediction mode, determine The prediction block for the chroma components of the current decoded block.

In this possible example, the determining the prediction block of the chrominance component of the currently decoded block according to the luma component intra prediction mode includes: determining the currently decoded block according to the luma component intra prediction mode the reference prediction block of the chrominance component of the block; filtering the reference prediction block of the chrominance component of the current decoding block to obtain the prediction block of the chrominance component of the current decoding block.

In a specific implementation, the device may determine that the chrominance component intra prediction mode indicates that the luminance component of the current decoding block is used to determine the the chroma components of the current decoded block. The preset intra prediction mode is a luminance component intra prediction mode in a preset direction, and the preset direction includes but is not limited to the horizontal direction (for example: the direction along the X axis in the two-dimensional rectangular coordinate system XoY as shown in FIG. 1 ) ), the vertical direction (for example: the negative direction along the Y axis in the two-dimensional rectangular coordinate system XoY as shown in Figure 1).

In this possible example, the filtering the reference prediction block of the chroma component of the current decoding block includes: using a third filter to filter the reference prediction block of the chroma component of the current decoding block.

In this possible example, the third filter includes a filter for filtering the left boundary pixel area of the reference prediction block for the chrominance component and a reference prediction block for the chrominance component The filter that filters the non-left boundary pixel area.

In this possible example, the filter for filtering the left boundary pixel region of the reference prediction block of the chrominance component includes a third two-tap filter; the third two-tap filter includes:

P _C (x, y)=(P' _C (2x, 2y)+P' _C (2x, 2y+1)+1)>>1

Wherein, x, _y are the coordinates of the pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast samples.

In this possible example, the filter for filtering the non-left boundary pixel region of the reference prediction block of the chrominance component includes a first six-tap filter; the first six-tap filter includes :

Wherein, x, y are the coordinates of the current pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, _Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast sample.

In this possible example, the determining the reference prediction block of the chrominance component of the current decoding block according to the luminance component intra prediction mode includes: determining the current decoding block according to the luminance component intra prediction mode A reconstructed block of the luminance component of the decoded block; and a reference prediction block of the chrominance component of the current decoded block is determined according to the reconstructed block of the luminance component of the current decoded block.

The size of the reference prediction block of the chrominance component is the same as the size of the reconstructed block of the luminance component. For example, as shown in FIG. 8 , the reconstructed block of the luminance component and the reference prediction block of the chrominance component in the prediction process are both 8*8 pixel arrays.

In this possible example, the determining, according to the reconstructed block of the luminance component of the current decoding block, the reference prediction block of the chrominance component of the current decoding block includes: determining to use the luminance component of the current decoding block A linear model for performing cross-component prediction on the reconstructed block; calculating the reconstructed block of the luminance component according to the linear model to obtain a reference prediction block of the chrominance component of the current decoding block.

Wherein, the linear model may be, for example, the linear model of the aforementioned formulas (1) or (2) and (3).

In this possible example, the determining a linear model for performing cross-component prediction using the reconstructed block of the luminance component of the current decoding block includes: determining a reference pixel for calculating the linear model, the reference pixel including at least one adjacent pixel of the current decoding block; calculating the linear model from the reference pixel.

Wherein, the selection of the reference pixels for calculating the linear model may be extended to the adjacent pixels on the lower left side, the left side, the upper left side, the upper side and the upper right side of the current decoding block.

In this possible example, the determining a reference pixel for calculating the linear model includes: according to available information of reconstructed samples of adjacent pixels of the current decoding block and the chrominance component intra prediction mode , determine the reference pixels used to calculate the linear model.

Wherein, the chrominance component intra prediction mode of the current decoding block includes any one of TSCPM_T, TSCPM_L, MCPM_T, and MCPM L. The available information specifically includes available on both sides and available on one side (for example: available on the left side and available on the right side). It can be seen that in this example, the reference adjacent pixels used for calculating the coefficients of the linear model can be flexibly set according to the availability of reconstructed samples of adjacent pixels and the intra prediction mode of the chrominance component.

In this possible example, the determining a reference pixel for calculating the linear model includes: determining a luminance component intra prediction mode with an optimal rate-distortion cost of adjacent decoding blocks of the current decoding block, determining Reference pixels for computing the linear model. Wherein, the intra prediction mode with the optimal rate distortion cost of the luminance component of the adjacent decoding block may be the same as or different from the intra prediction mode with the optimal rate distortion cost of the luminance component of the current decoding block.

Step 230: Perform prediction modification on the prediction block of the chrominance component of the current decoding block to obtain the modified prediction block of the chrominance component of the current decoding block.

In this possible example, the performing prediction modification on the prediction block of the chrominance component of the current decoding block includes: determining a filter according to the chrominance component intra prediction mode; The prediction block of the chrominance component of the currently decoded block performs prediction correction.

Wherein, the filtering direction of the filter is orthogonal to the direction of the adjacent pixels of the chrominance component intra prediction mode used to calculate the linear model relative to the current coding block, and the correlation of the adjacent pixels on the boundary of the orthogonal direction can be synthesized. predicts the predicted samples of the chroma component of each pixel.

In this possible example, the determining the filter according to the chrominance component intra prediction mode includes: when the chrominance component intra prediction mode is TSCPM_T or MCPM T or a normal intra vertical angle-like prediction mode , the filter is set as the first filter.

In this possible example, the first filter is configured to perform the filtering of the pixel area adjacent to the left border of the prediction block of the chroma component of the current decoding block and the prediction block of the chroma component of the current decoding block The pixel area of is filtered.

In this possible example, the first filter includes a first two-tap filter; the first two-tap filter includes:

P'(x,y)=f(x)·P(-1,y)+(1-f(x))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current decoding block, the value of y does not exceed the high value range of the current decoding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the decoded block, P(-1, y) is the reconstructed sample of the pixel located in row y adjacent to the left boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In this possible example, the horizontal filter coefficients are determined by a first set of parameters, and the first set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(-1, y) the distance between.

In this possible example, the determining the filter according to the chrominance component intra prediction mode includes: when the chrominance component intra prediction mode is TSCPM_L or MCPM_L or a normal intra horizontal angle prediction mode, The filter is set as a second filter.

In this possible example, the second filter is configured to perform the filtering of the pixel region adjacent to the upper boundary of the prediction block of the chrominance component of the current decoding block and the prediction block of the chrominance component of the current decoding block The pixel area of is filtered.

In this possible example, the second filter includes a second two-tap filter; the second two-tap filter includes:

P'(x,y)=f(y)·P(x,-1)+(1-f(y))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chrominance component of the coding block, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In this possible example, the vertical filter coefficients are determined by a second set of parameters, the second set of parameters including the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(x, − 1) the distance between.

The value of the vertical filter coefficient is related to the size of the chrominance component of the current decoding block and the distance between the predicted pixel and the left adjacent pixel in the prediction block of the current chrominance component.

Specifically, the selection of the above-mentioned filter coefficients is related to the size of the chrominance component, and is divided into different filter coefficient groups according to the size of the prediction block of the chrominance component of the current decoding block, and is selected according to the size of the prediction block of the current chrominance component. The corresponding set of filter coefficients. The selection of the above-mentioned vertical filter coefficients is related to the distance from the predicted pixel to the adjacent pixel on the upper side, and the distance from the currently predicted pixel to the adjacent pixel on the upper side is used as the index value, and the corresponding filter coefficient is selected from the corresponding filter coefficient group. . The intra-frame chrominance prediction filter coefficients are specifically shown in Table 1.

In addition, the filter coefficients of this technology can use a coefficient truncation method to reduce coefficient storage, that is, the filter coefficients of all pixels whose distances from the currently predicted pixel to the upper adjacent pixel are greater than 10 are consistent.

In the specific implementation, after the prediction block of the chrominance component of the current decoding block is determined, the device may further calculate the reconstructed block of the chrominance component, and determine the reconstructed block of the current decoding block according to the reconstructed block of the chrominance component and the reconstructed block of the luminance component. compose the image.

In this possible example, the determining the filter according to the chrominance component intra prediction mode includes: when the chrominance component intra prediction mode is a normal intra non-angular prediction mode, setting the filter to is the third filter.

In this possible example, the third filter is used for predicting the pixel region adjacent to the left border of the prediction block of the chroma component of the current decoding block and the chroma component of the current decoding block The pixel area adjacent to the upper boundary of the block and the pixel area of the prediction block of the chrominance component of the current decoding block are filtered.

In this possible example, the third filter includes a first three-tap filter;

The first three-tap filter includes:

P'(x, y)=f(x)·P(-1,y)+f(y)·P(x,-1)+(1-f(x)-f(y))·P( x, y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the coding block, P(-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left boundary, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) of the pixel (x, y), f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In this possible example, the horizontal filter coefficients are determined by a first set of parameters, and the first set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(-1, y) the distance between;

The vertical filter coefficients are determined by a second set of parameters including the size of the prediction block of the chrominance components and the distance between pixel (x,y) and pixel P(x,-1).

It can be seen that, in the embodiment of the present application, compared with the prior art, the solution of the present application uses the spatial correlation between the adjacent coding block and the current coding block to correct the chrominance of the current coding block in the chrominance component intra prediction mode. Prediction samples of components to improve prediction accuracy and decoding efficiency.

In a possible example, the performing prediction correction on the prediction block of the chrominance component of the current decoding block includes: parsing the code stream to obtain a chrominance correction flag bit; determining a value of the chrominance correction flag bit The numerical value is a first numerical value, and the first numerical value is used to indicate that a filter is used to perform the prediction modification; the prediction modification is performed on the prediction block of the chrominance component of the current decoding block. It can be seen that, in this example, the prediction correction is directly indicated by the flag bit.

In this possible example, the method further includes: determining the value of the chrominance correction flag to be a second value, where the second value is used to indicate that a filter is not used to perform the prediction correction.

In this possible example, the chrominance correction flag is shared with the luminance correction flag. No additional identification bits will be added, saving the transmission code stream.

In this possible example, the chrominance correction flags are used independently. Instructions are clearer and more efficient.

The proposed technology is implemented on the AVS reference software HPM6.0, and the full intra-frame mode and random access mode are tested in a 1-second sequence under general test conditions and video sequences. The specific performances are shown in Tables 2 and 3.

Table 2 All internal All Intra test results

Table 3 Random Access Random Access test results

It can be seen from Table 2 and Table 3 that the UV component of the test sequence has an average performance gain, the U component has an average coding performance improvement of 0.71% under the AI test condition, and the V component has an average coding performance of 1.35% under the RA test condition. Performance improvements.

An embodiment of the present application provides an image encoding apparatus, and the image encoding apparatus may be a video decoder or a video encoder. Specifically, the image encoding apparatus is configured to perform the steps performed by the video decoder in the above decoding method. The image encoding apparatus provided in the embodiments of the present application may include modules corresponding to corresponding steps.

In this embodiment of the present application, the image coding apparatus may be divided into functional modules according to the foregoing method examples. For example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The above-mentioned integrated modules can be implemented in the form of hardware, and can also be implemented in the form of software function modules. The division of modules in the embodiments of the present application is schematic, and is only a logical function division, and there may be other division manners in actual implementation.

In the case where each functional module is divided according to each function, FIG. 14 shows a possible schematic structural diagram of the image coding apparatus involved in the above embodiment. As shown in FIG. 14 , the image coding apparatus 14 includes a dividing unit 140 , a determining unit 141 , and a correcting unit 142 .

a dividing unit 140, configured to divide the image, and determine the intra prediction mode of the chrominance component of the current coding block;

a determining unit 141, configured to determine the prediction block of the chrominance component of the current coding block according to the chrominance component intra prediction mode;

The modification unit 142 is configured to perform prediction modification on the prediction block of the chrominance component of the current coding block to obtain the modified prediction block of the chrominance component of the current coding block.

In this possible example, in the aspect of performing prediction modification on the prediction block of the chrominance component of the current coding block, the modification unit 142 is specifically configured to determine a filter according to the intra prediction mode of the chrominance component ; and using the filter to perform prediction modification on the prediction block of the chrominance component of the current coding block.

In this possible example, in the aspect of determining the filter according to the chrominance component intra prediction mode, the modifying unit 142 is specifically configured to: when the chrominance component intra prediction mode is two-step cross-component prediction When the mode TSCPM_T or multiple cross-component prediction modes MCPM_T or the normal intra vertical class angle prediction mode is used, the filter is set as the first filter.

In this possible example, the first filter is configured to perform the filtering of a pixel region adjacent to the left border of the prediction block of the chroma component of the current coding block and the prediction block of the chroma component of the current coding block The pixel area of is filtered.

In this possible example, the first filter includes a first two-tap filter;

The first two-tap filter includes:

P'(x,y)=f(x)·P(-1,y)+(1-f(x))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the coding block, P(-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In this possible example, the horizontal filter coefficients are determined by a first set of parameters, and the first set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(-1, y) the distance between.

In this possible example, in the aspect of determining the filter according to the chrominance component intra prediction mode, the modification unit 142 is specifically configured to, when the chrominance component intra prediction mode is TSCPM_L or MCPM_L or normal In the intra-horizontal-like angle prediction mode, the filter is set as the second filter.

In this possible example, the second filter is used to perform the filtering of the pixel region adjacent to the upper boundary of the prediction block of the chrominance component of the current coding block and the prediction block of the chrominance component of the current coding block The pixel area of is filtered.

In this possible example, the second filter includes a second two-tap filter;

The second two-tap filter includes:

P'(x,y)=f(y)·P(x,-1)+(1-f(y))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chrominance component of the coding block, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In this possible example, the vertical filter coefficients are determined by a second set of parameters, the second set of parameters including the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(x, − 1) the distance between.

In this possible example, in the aspect of determining the filter according to the chrominance component intra prediction mode, the modifying unit 142 is specifically configured to: when the chrominance component intra prediction mode is a normal intra non-angle In prediction mode, the filter is set as the third filter.

In this possible example, the third filter is used for predicting the pixel region adjacent to the left boundary of the prediction block of the chroma component of the current coding block and the chroma component of the current coding block The pixel area adjacent to the upper boundary of the block and the pixel area of the prediction block of the chrominance component of the current coding block are filtered.

In this possible example, the third filter includes a first three-tap filter;

The first three-tap filter includes:

P'(x, y)=f(x)·P(-1,y)+f(y)·P(x,-1)+(1-f(x)-f(y))·P( x, y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the coding block, P(-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left boundary, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) of the pixel (x, y), f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In this possible example, the horizontal filter coefficients are determined by a first set of parameters, and the first set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(-1, y) the distance between;

The vertical filter coefficients are determined by a second set of parameters including the size of the prediction block of the chrominance components and the distance between pixel (x,y) and pixel P(x,-1).

In this possible example, in the aspect of performing prediction modification on the prediction block of the chrominance component of the current coding block, the modification unit 142 is specifically configured to calculate the first number of the current coding block without modification. a rate-distortion cost, and calculating a second rate-distortion cost for the corrected case of the current coding block; and determining that the first rate-distortion cost is greater than the second rate-distortion cost; and The prediction block of the chrominance component performs prediction correction.

In this possible example, in the aspect of performing prediction modification on the prediction block of the chrominance component of the current coding block, the modification unit 142 is specifically configured to calculate the first number of the current coding block without modification. A rate-distortion cost, and calculating a second rate-distortion cost under the corrected condition of the current coding block; and determining that the first rate-distortion cost is greater than the second rate-distortion cost, and setting the chrominance correction flag to the first rate-distortion cost A numerical value, the first numerical value is used to indicate that the prediction modification needs to be performed; and the prediction modification is performed on the prediction block of the chrominance component of the current coding block.

In this possible example, the determining unit 141 is further configured to determine that the first rate-distortion cost is less than or equal to the second rate-distortion cost, and set the chrominance correction flag to a second value, and the The second value is used to indicate that the prediction modification is not required.

In this possible example, the chrominance correction flag is shared with the luminance correction flag.

In this possible example, the chrominance correction flags are used independently.

In this possible example, in the aspect of determining the prediction block of the chrominance component of the current coding block according to the chrominance component intra prediction mode, the determining unit 141 is specifically configured to determine the current coding a luma component intra-prediction mode for a block; and when the chroma component intra-prediction mode indicates use of the luma component of the current coded block to determine a predicted value for the chroma component of the current coded block, according to the luma component Intra prediction mode, which determines the prediction block of the chroma component of the current coding block.

In this possible example, in the aspect of determining the prediction block of the chrominance component of the current coding block according to the luminance component intra prediction mode, the determining unit 141 is specifically configured to, according to the luminance component frame Intra-prediction mode, determining the reference prediction block of the chroma component of the current coding block; and filtering the reference prediction block of the chroma component of the current coding block to obtain the prediction block of the chroma component of the current coding block .

In this possible example, in the aspect of filtering the reference prediction block of the chrominance component of the current coding block, the determining unit 141 is specifically configured to use a third filter to filter the chrominance of the current coding block The reference prediction block of the degree component is filtered.

In this possible example, the third filter includes a filter for filtering the left boundary pixel area of the reference prediction block for the chrominance component and a reference prediction block for the chrominance component The filter that filters the non-left boundary pixel area.

In this possible example, the filter for filtering the left boundary pixel region of the reference prediction block of the chrominance component comprises a third two-tap filter;

The third two-tap filter includes:

P _C (x, y)=(P' _C (2x, 2y)+P' _C (2x, 2y+1)+1)>>1

Wherein, x, _y are the coordinates of the pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast samples.

In this possible example, the filter for filtering the non-left boundary pixel region of the reference prediction block of the chrominance component comprises a first six-tap filter;

The first six-tap filter includes:

Wherein, x, y are the coordinates of the current pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, _Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast sample.

In this possible example, in the aspect of determining the reference prediction block of the chrominance component of the current coding block according to the luma component intra prediction mode, the determining unit 141 is specifically configured to: according to the luma component an intra-frame prediction mode, determining a reconstructed block of the luma component of the current coding block; and determining a reference prediction block of the chroma component of the current coding block according to the reconstructed block of the luma component of the current coding block.

In this possible example, in the aspect of determining the reference prediction block of the chrominance component of the current coding block according to the reconstructed block of the luminance component of the current coding block, the determining unit 141 is specifically configured to: determine A linear model for cross-component prediction using the reconstructed block of the luminance component of the current coding block; and calculating the reconstructed block of the luminance component according to the linear model to obtain a reference prediction of the chrominance component of the current coding block piece.

In this possible example, in the aspect of determining a linear model for performing cross-component prediction by using the reconstructed block of the luminance component of the current coding block, the determining unit 141 is specifically configured to determine a linear model for calculating the linear model , the reference pixel includes at least one neighboring pixel of the current coding block; and the linear model is calculated from the reference pixel.

In this possible example, in the aspect of determining the reference pixels for calculating the linear model, the determining unit 141 is specifically configured to, according to the available information of the reconstructed samples of the adjacent pixels of the current coding block and The chrominance component intra prediction mode determines the reference pixels used to calculate the linear model.

In this possible example, in the aspect of determining the reference pixels for calculating the linear model, the determining unit 141 is specifically configured to optimize the rate-distortion cost according to the rate-distortion cost of adjacent coding blocks of the current coding block The intra prediction mode of the luma component determines the reference pixels used to calculate the linear model.

In this possible example, in the aspect of determining the prediction block of the chrominance component of the current coding block according to the chrominance component intra prediction mode, the determining unit 141 is specifically configured to: according to the current coding available information of reconstructed samples of neighboring pixels of the block and the chrominance component intra prediction mode, determine a reference pixel; and determine a prediction block of the chrominance component of the current coding block from the reference pixel.

Wherein, all relevant contents of the steps involved in the above method embodiments can be cited in the functional descriptions of the corresponding functional modules, which will not be repeated here. Of course, the image encoding apparatus provided in the embodiment of the present application includes but is not limited to the above-mentioned modules. For example, the image encoding apparatus may further include a storage unit 143 . The storage unit 143 may be used to store program codes and data of the image encoding apparatus.

In the case of using an integrated unit, a schematic structural diagram of the image encoding apparatus provided by the embodiment of the present application is shown in FIG. 15 . In FIG. 15 , the image encoding apparatus 15 includes a processing module 150 and a communication module 151 . The processing module 150 is used to control and manage the actions of the image encoding apparatus, eg, to perform the steps performed by the division unit 140 , the determination unit 141 , the modification unit 142 , and/or other processes for performing the techniques described herein. The communication module 151 is used to support the interaction between the image coding apparatus and other devices. As shown in FIG. 15 , the image coding apparatus may further include a storage module 152 , which is used for storing program codes and data of the image coding apparatus, for example, the content stored in the above-mentioned storage unit 143 .

The processing module 150 may be a processor or a controller, such as a central processing unit (Central Processing Unit, CPU), a general-purpose processor, a digital signal processor (Digital Signal Processor, DSP), ASIC, FPGA or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It may implement or execute the various exemplary logical blocks, modules and circuits described in connection with this disclosure. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and the like. The communication module 151 may be a transceiver, an RF circuit, a communication interface, or the like. The storage module 152 may be a memory.

Wherein, all the relevant contents of the scenarios involved in the above method embodiments can be cited in the functional description of the corresponding functional module, which will not be repeated here. The image encoding device 14 and the image encoding device 15 can both execute the image encoding method shown in FIG. 12A , and the image encoding device 14 and the image encoding device 15 may be video image encoding devices or other devices with video encoding functions.

The present application also provides a video encoder, including a non-volatile storage medium, and a central processing unit, where the non-volatile storage medium stores an executable program, and the central processing unit is connected to the non-volatile storage medium. The medium is connected, and the executable program is executed to implement the image encoding method of the embodiment of the present application.

An embodiment of the present application provides an image decoding apparatus, and the image decoding apparatus may be a video decoder or a video decoder. Specifically, the image decoding apparatus is configured to perform the steps performed by the video decoder in the above decoding method. The image decoding apparatus provided by the embodiments of the present application may include modules corresponding to corresponding steps.

In the embodiments of the present application, the image decoding apparatus may be divided into functional modules according to the above method examples. For example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The above-mentioned integrated modules can be implemented in the form of hardware, and can also be implemented in the form of software function modules. The division of modules in the embodiments of the present application is schematic, and is only a logical function division, and there may be other division manners in actual implementation.

In the case where each functional module is divided according to each function, FIG. 16 shows a possible schematic structural diagram of the image decoding apparatus involved in the above embodiment. As shown in FIG. 16 , the image decoding device 16 includes an analysis unit 160 , a determination unit 161 , and a correction unit 162 .

a parsing unit 160, configured to parse the code stream and determine the intra-prediction mode of the chroma component of the current decoding block;

a determining unit 161, configured to determine the prediction block of the chrominance component of the current decoding block according to the chrominance component intra prediction mode;

The modification unit 162 is configured to perform prediction modification on the prediction block of the chrominance component of the current decoding block to obtain the modified prediction block of the chrominance component of the current decoding block.

In a possible example, in the aspect of performing prediction modification on the prediction block of the chrominance component of the current decoding block, the modification unit 162 is specifically configured to: determine a filter according to the intra prediction mode of the chrominance component ; and using the filter to perform prediction modification on the prediction block of the chrominance component of the current decoding block.

In a possible example, in the aspect of determining the filter according to the chrominance component intra prediction mode, the modifying unit 162 is specifically configured to: when the chrominance component intra prediction mode is TSCPM_T or MCPM_T or normal In the intra vertical angle-like prediction mode, the filter is set as the first filter.

In a possible example, the first filter is configured to perform filtering on a pixel region adjacent to the left boundary of the prediction block of the chroma component of the current decoding block and the prediction block of the chroma component of the current decoding block The pixel area of is filtered.

In a possible example, the first filter includes a first two-tap filter;

The first two-tap filter includes:

P'(x,y)=f(x)·P(-1,y)+(1-f(x))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current decoding block, the value of v does not exceed the high value range of the current decoding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the decoded block, P(-1, y) is the reconstructed sample of the pixel located in row y adjacent to the left boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In a possible example, the horizontal filter coefficient is determined by a first set of parameters, the first set of parameters includes the size of the prediction block of the chrominance component and the pixel (x, y) and the pixel P(-1, y) the distance between.

In a possible example, the determining a filter according to the chrominance component intra prediction mode includes:

When the chrominance component intra prediction mode is TSCPM_L or MCPM_L or a normal intra horizontal-like angle prediction mode, the filter is set as the second filter.

In a possible example, the second filter is configured to perform the filtering on a pixel area adjacent to an upper boundary of the prediction block of the chroma component of the current decoding block and the prediction block of the chroma component of the current decoding block The pixel area of is filtered.

In a possible example, the second filter includes a second two-tap filter;

The second two-tap filter includes:

P'(x,y)=f(y)·P(x,-1)+(1-f(y))·P(x,y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chrominance component of the coding block, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In a possible example, the vertical filter coefficients are determined by a second set of parameters, and the second set of parameters includes the size of the prediction block of the chrominance component and the size of the pixel (x, y) and the pixel P(x, − 1) the distance between.

In a possible example, in the aspect of determining the filter according to the chrominance component intra prediction mode, the modifying unit 162 is specifically configured to: when the chrominance component intra prediction mode is a normal intra non-angle In prediction mode, the filter is set as the third filter.

In a possible example, the third filter is used for predicting the pixel region adjacent to the left border of the prediction block of the chroma component of the current decoding block and the chroma component of the current decoding block The pixel area adjacent to the upper boundary of the block and the pixel area of the prediction block of the chrominance component of the current decoding block are filtered.

In a possible example, the third filter includes a first three-tap filter;

The first three-tap filter includes:

P'(x, y)=f(x)·P(-1,y)+f(y)·P(x,-1)+(1-f(x)-f(y))·P( x, y)

Among them, x, y are the coordinates of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of v does not exceed the high value range of the current coding block, and P'(x, y) is the current The final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the coding block, P(-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left boundary, P(x, -1) is the reconstructed sample of the pixel located in the X column adjacent to the upper boundary, f(x) is the horizontal filter coefficient of the reference pixel P(-1, y) of the pixel (x, y), f(y) is the vertical filter coefficient of the reference pixel P(x, -1) for the pixel (x, y), and P(x, y) is the original prediction sample of the pixel (x, y).

In a possible example, the horizontal filter coefficient is determined by a first set of parameters, the first set of parameters includes the size of the prediction block of the chrominance component and the pixel (x, y) and the pixel P(-1, y) the distance between;

The vertical filter coefficients are determined by a second set of parameters including the size of the prediction block of the chrominance components and the distance between pixel (x,y) and pixel P(x,-1).

In a possible example, in the aspect of performing prediction modification on the prediction block of the chrominance component of the current decoding block, the modification unit 162 is specifically configured to: parse the code stream to obtain a chrominance modification flag bit and determine that the numerical value of the chrominance correction flag bit is a first numerical value, and the first numerical value is used to indicate that a filter is used to carry out the prediction modification; and the prediction block of the chrominance component of the current decoding block is predicted Correction.

In a possible example, the determining unit 161 is further configured to determine the value of the chrominance correction flag bit as a second value, where the second value is used to indicate that a filter is not used to perform the prediction correction.

In a possible example, the chrominance correction flag bit is shared with the luminance correction flag bit.

In a possible example, the chrominance correction flags are used independently.

In a possible example, in the aspect of determining the prediction block of the chrominance component of the current decoding block according to the chrominance component intra prediction mode, the determining unit 161 is specifically configured to determine the current decoding block a luma component intra-prediction mode for a block; and when the chroma component intra-prediction mode indicates using the luma component of the currently decoded block to determine a predicted value for the chroma component of the current decoded block, according to the luma component Intra prediction mode, which determines the prediction block for the chroma components of the currently decoded block.

In a possible example, in the aspect of determining the prediction block of the chrominance component of the current decoding block according to the luminance component intra prediction mode, the determining unit 161 is specifically configured to: according to the luminance component frame Intra-prediction mode, determining the reference prediction block of the chroma component of the current decoding block; and filtering the reference prediction block of the chroma component of the current decoding block to obtain the prediction block of the chroma component of the current decoding block .

In a possible example, in the aspect of filtering the reference prediction block of the chroma component of the current decoding block, the determining unit 161 is specifically configured to: use a third filter to filter the chroma components of the current decoding block The reference prediction block of the degree component is filtered.

In a possible example, the third filter includes a filter for filtering the left boundary pixel area of the reference prediction block of the chrominance component and a reference prediction block for the chrominance component The filter that filters the non-left boundary pixel area.

In a possible example, the filter for filtering the left boundary pixel region of the reference prediction block of the chrominance component includes a third two-tap filter;

The third two-tap filter includes:

P _C (x, y)=(P' _C (2x, 2y)+P' _C (2x, 2y+1)+1)>>1

Wherein, x, _y are the coordinates of the pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast samples.

In a possible example, the filter for filtering the non-left boundary pixel region of the reference prediction block of the chrominance component includes a first six-tap filter;

The first six-tap filter includes:

Wherein, x, y are the coordinates of the current pixel, _P'c is the prediction sample of the pixel in the reference prediction block of the chrominance component, _Pc is the chrominance component of the current pixel in the prediction block of the chrominance component forecast sample.

In a possible example, in the aspect of determining the reference prediction block of the chrominance component of the current decoding block according to the luminance component intra prediction mode, the determining unit 161 is specifically configured to: according to the luminance component an intra-frame prediction mode, determining a reconstructed block of the luma component of the current decoding block; and determining a reference prediction block of the chroma component of the current decoding block according to the reconstructed block of the luma component of the current decoding block.

In a possible example, in the aspect of determining the reference prediction block of the chrominance component of the current decoding block according to the reconstructed block of the luminance component of the current decoding block, the determining unit 161 is specifically configured to: determine A linear model for cross-component prediction using the reconstructed block of the luma component of the current decoding block; and calculating the reconstructed block of the luma component according to the linear model to obtain a reference prediction of the chroma component of the current decoding block piece.

In a possible example, in the aspect of determining a linear model for performing cross-component prediction by using the reconstructed block of the luminance component of the current decoding block, the determining unit 161 is specifically configured to: determine a linear model for calculating the linear model , the reference pixel includes at least one neighboring pixel of the current decoding block; and the linear model is calculated from the reference pixel.

In a possible example, in the aspect of determining the reference pixels for calculating the linear model, the determining unit 161 is specifically configured to: according to available information of reconstructed samples of adjacent pixels of the current decoding block and The chrominance component intra prediction mode determines the reference pixels used to calculate the linear model.

In a possible example, in the aspect of determining the reference pixels for calculating the linear model, the determining unit 161 is specifically configured to: optimize the rate-distortion cost according to the rate-distortion cost of adjacent decoding blocks of the current decoding block The intra prediction mode of the luma component determines the reference pixels used to calculate the linear model.

In a possible example, in the aspect of determining the prediction block of the chrominance component of the current decoding block according to the chrominance component intra prediction mode, the determining unit 161 is specifically configured to: according to the current decoding available information of reconstructed samples of neighboring pixels of the block and the chrominance component intra prediction mode, determine a reference pixel; and determine a prediction block of the chrominance component of the currently decoded block from the reference pixel.

Wherein, all relevant contents of the steps involved in the above method embodiments can be cited in the functional descriptions of the corresponding functional modules, which will not be repeated here. Of course, the image decoding apparatus provided in the embodiment of the present application includes but is not limited to the above-mentioned modules. For example, the image decoding apparatus may further include a storage unit 163 . The storage unit 163 may be used to store program codes and data of the image decoding apparatus.

In the case of using an integrated unit, a schematic structural diagram of an image decoding apparatus provided by an embodiment of the present application is shown in FIG. 17 . In FIG. 17 , the image decoding apparatus 17 includes a processing module 170 and a communication module 171 . The processing module 170 is used to control and manage the actions of the image decoding apparatus, eg, to perform the steps performed by the parsing unit 160, the determining unit 161, the modifying unit 162, and/or other processes for performing the techniques described herein. The communication module 171 is used to support the interaction between the image decoding apparatus and other devices. As shown in FIG. 17 , the image decoding apparatus may further include a storage module 172 . The storage module 172 is configured to store program codes and data of the image decoding apparatus, for example, to store the content stored in the above-mentioned storage unit 163 .

The processing module 170 may be a processor or a controller, such as a central processing unit (Central Processing Unit, CPU), a general-purpose processor, a digital signal processor (Digital Signal Processor, DSP), ASIC, FPGA or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It may implement or execute the various exemplary logical blocks, modules and circuits described in connection with this disclosure. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and the like. The communication module 171 may be a transceiver, an RF circuit, a communication interface, or the like. The storage module 172 may be a memory.

Wherein, all the relevant contents of the scenarios involved in the above method embodiments can be cited in the functional description of the corresponding functional module, which will not be repeated here. The image decoding apparatus 16 and the image decoding apparatus 17 can both execute the image decoding method shown in FIG. 13 , and the image decoding apparatus 16 and the image decoding apparatus 17 may be video image decoding apparatuses or other devices with video decoding functions.

The present application also provides a video decoder, including a non-volatile storage medium, and a central processing unit, where the non-volatile storage medium stores an executable program, and the central processing unit is connected to the non-volatile storage medium. The medium is connected, and the executable program is executed to implement the image decoding method of the embodiment of the present application.

The present application also provides a terminal, where the terminal includes: one or more processors, a memory, and a communication interface. The memory and the communication interface are coupled with one or more processors; the memory is used to store computer program codes, and the computer program codes include instructions. When the one or more processors execute the instructions, the terminal executes the image encoding and/or the image coding and/or the embodiments of the present application. or image decoding method. The terminal here can be a video display device, a smart phone, a portable computer, and other devices that can process or play videos.

Another embodiment of the present application further provides a computer-readable storage medium, where the computer-readable storage medium includes one or more program codes, and the one or more programs include instructions, when the processor in the decoding device executes the program When coding, the decoding device executes the image encoding method and the image decoding method of the embodiments of the present application.

In another embodiment of the present application, a computer program product is also provided, the computer program product includes computer-executable instructions, and the computer-executable instructions are stored in a computer-readable storage medium; at least one processor of the decoding device can be obtained from a computer The readable storage medium reads the computer-executable instruction, and at least one processor executes the computer-executable instruction to cause the terminal to implement the image encoding method and the image decoding method of the embodiments of the present application.

In the above-mentioned embodiments, it may be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using a software program, it may take the form of a computer program product, in whole or in part. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated.

The computer may be a general purpose computer, special purpose computer, computer network, or other programmable device. The computer instructions may be stored in or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions may be downloaded from a website site, computer, server or data center Transmission to another website site, computer, server, or data center by wire (eg, coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (eg, infrared, wireless, microwave, etc.).

The computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that includes an integration of one or more available media. The available media may be magnetic media (eg, floppy disks, hard disks, magnetic tapes), optical media (eg, DVD), or semiconductor media (eg, Solid State Disk (SSD)), and the like.

From the description of the above embodiments, those skilled in the art can clearly understand that for the convenience and brevity of the description, only the division of the above functional modules is used as an example for illustration. In practical applications, the above functions can be allocated as required. It is completed by different functional modules, that is, the internal structure of the device is divided into different functional modules, so as to complete all or part of the functions described above.

In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the device embodiments described above are only illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be Incorporation may either be integrated into another device, or some features may be omitted, or not implemented. On the other hand, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, indirect coupling or communication connection of devices or units, and may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place, or may be distributed to multiple different places . Some or all of the units may be selected according to actual needs to achieve the purpose of the solution in this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware, or may be implemented in the form of software functional units.

If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a readable storage medium. Based on such understanding, the technical solutions of the embodiments of the present application can be embodied in the form of software products in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, which are stored in a storage medium , including several instructions to make a device (may be a single chip microcomputer, a chip, etc.) or a processor (processor) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), magnetic disk or optical disk and other media that can store program codes .

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited to this, and any changes or substitutions within the technical scope disclosed in the present application should be covered within the protection scope of the present application. . Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims (37)

1. An image encoding method, comprising:

dividing the image, and determining a chroma component intra-frame prediction mode of a current coding block;

determining a prediction block of the chroma component of the current coding block according to the chroma component intra-frame prediction mode;

and correcting the prediction block of the chroma component of the current coding block to obtain the corrected prediction block of the chroma component of the current coding block.

2. The method of claim 1, wherein modifying the prediction block for the chroma component of the current coding block comprises:

determining a filter according to the chroma component intra prediction mode;

filtering a prediction block of a chroma component of the current coding block using the filter.

3. The method of claim 2, wherein the determining a filter according to the chroma component intra prediction mode comprises:

the filter is a first filter when the chroma component intra prediction mode is a two-step cross component prediction mode TSCPM _ T or an intra vertical class angle prediction mode.

4. The method of claim 3, wherein the first filter is configured to filter a pixel region adjacent to a left boundary of a chroma component of the current coding block and a prediction value of a prediction block of the chroma component of the current coding block.

5. The method of claim 4, wherein the pixel region adjacent to the left boundary of a chroma component of the current coding block contains chroma reconstruction pixels left adjacent to the current coding block.

6. The method of claim 4, wherein the first filter comprises a first two-tap filter;

the first two-tap filter comprises:

P'(x，y)＝f(x)·P(-1，y)+(1-f(x))·P(x，y)

wherein x, y is the coordinate of the current pixel, the value of x does not exceed the wide value range of the current coding block, the value of y does not exceed the high value range of the current coding block, P' (x, y) is the final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the current coding block, P (-1, y) is the reconstruction sample of the pixel adjacent to the left side boundary in the y row, f (x) is the horizontal filter coefficient of the pixel (x, y) reference reconstruction sample P (-1, y), and P (x, y) is the original prediction sample of the pixel (x, y).

7. The method of claim 6, wherein the filter coefficients of the first filter are determined by a look-up table in which filter coefficients are indexed by the size of a prediction block of the chroma component and the distance between pixel (x, y) and pixel (-1, y).

8. The method of claim 2, wherein determining a filter according to the chroma component intra prediction mode comprises:

the filter is a second filter when the chroma component intra prediction mode is TSCPM L or intra horizontal class angular prediction mode.

9. The method of claim 8, wherein the second filter is configured to filter a pixel region adjacent to an upper boundary of a chroma component of the current coding block and a prediction value of a prediction block of the chroma component of the current coding block.

10. The method of claim 9, wherein the pixel region adjacent to the upper boundary of a chroma component of the current coding block contains chroma reconstructed pixels adjacent to the current coding block.

11. The method of claim 9, wherein the second filter comprises a second two-tap filter;

the second two-tap filter comprises:

P(x，y)＝f(y)·P(x，-1)+(1-f(y))·P(x，y)

where X, y is the coordinate of the current pixel, X does not exceed the wide value range of the current coding block, y does not exceed the high value range of the current coding block, P' (X, y) is the final prediction sample of the pixel (X, y) of the prediction block of the chroma component of the current coding block, P (X, -1) is the reconstructed sample of the pixel adjacent to the upper boundary in the X column, f (y) is the vertical filter coefficient of the pixel (X, y) reference reconstructed sample P (X, -1), and P (X, y) is the original prediction sample of the pixel (X, y).

12. The method according to claim 11, wherein the filter coefficients of the second filter are determined by a look-up table in which filter coefficients are indexed by the size of a prediction block of the chroma component and the distance between pixel (x, y) and pixel (x, -1).

13. The method of claim 1, wherein the performing prediction correction on the prediction block of the chroma component of the current coding block comprises:

calculating a first rate distortion cost of the current coding block under the unmodified condition and calculating a second rate distortion cost of the current coding block under the modified condition;

determining that the first rate distortion cost is greater than the second rate distortion cost, and setting a chrominance correction identification bit as a first numerical value, wherein the first numerical value is used for indicating that the prediction correction needs to be carried out;

and performing prediction correction on the prediction block of the chroma component of the current coding block.

14. The method of claim 1, wherein the performing prediction correction on the prediction block of the chroma component of the current coding block comprises:

calculating a first rate distortion cost of the current coding block under the unmodified condition and calculating a second rate distortion cost of the current coding block under the modified condition;

and determining that the first rate distortion cost is less than or equal to the second rate distortion cost, and setting the chroma correction identification bit as a second numerical value, wherein the second numerical value is used for indicating that the prediction correction is not needed.

15. The method according to claim 13 or 14, wherein the chroma correction flag is common to the luma correction flag.

16. An image decoding method, comprising:

analyzing the code stream, and determining a chroma component intra-frame prediction mode of a current decoding block;

determining a prediction block for a chroma component of the currently decoded block according to the chroma component intra prediction mode;

and correcting the prediction block of the chroma component of the current decoding block to obtain the corrected prediction block of the chroma component of the current decoding block.

17. The method of claim 16, wherein modifying the prediction block for the chroma components of the currently decoded block comprises:

determining a filter according to the chroma component intra prediction mode;

filtering a prediction block of chroma components of the currently decoded block using the filter.

18. The method of claim 17, wherein the determining a filter according to the chroma component intra prediction mode comprises:

the filter is a first filter when the chroma intra prediction mode is TSCPM _ T or intra vertical class angular prediction mode.

19. The method of claim 18, wherein the first filter is configured to filter a region of pixels adjacent to a left boundary of chroma components of the current decoded block and predictors of a prediction block for chroma components of the current decoded block.

20. The method of claim 19, wherein the pixel region adjacent to the left boundary of a chroma component of the current coding block contains chroma reconstruction pixels left adjacent to the current coding block.

21. The method of claim 19, wherein the first filter comprises a first two-tap filter;

the first two-tap filter comprises:

P'(x，y)＝f(x)·P(-1，y)+(1-f(x))·P(x，y)

where x, y are coordinates of the current pixel, the value of x does not exceed the wide range of the current decoded block, the value of y does not exceed the high range of the current decoded block, P' (x, y) is the final prediction sample of the pixel (x, y) of the prediction block of the chroma component of the current decoded block, P (-1, y) is the reconstructed sample of the pixel located in the y row adjacent to the left side boundary, f (x) is the horizontal filter coefficient of the pixel (x, y) reference reconstructed sample P (-1, y), and P (x, y) is the original prediction sample of the pixel (x, y).

22. The method of claim 21, wherein the filter coefficients of the first filter are determined by a look-up table in which the filter coefficients are indexed by the size of a prediction block of the chroma component and the distance between pixel (x, y) and pixel (-1, y).

23. The method of claim 17, wherein the determining a filter according to the chroma component intra prediction mode comprises:

the filter is a second filter when the chroma component intra prediction mode is TSCPM _ L or intra horizontal class angular prediction mode.

24. The method of claim 23, wherein the second filter is configured to filter a region of pixels adjacent to an upper boundary of a chroma component of the current decoded block and a prediction value of a prediction block of the chroma component of the current decoded block.

25. The method of claim 24, wherein the pixel region adjacent to the upper boundary of a chroma component of the current coding block contains chroma reconstructed pixels adjacent to the current coding block.

26. The method of claim 24, wherein the second filter comprises a second two-tap filter;

the second two-tap filter comprises:

P′(x,y)＝f(y).P(x,-1)+(1-f(y)).P(x，y)

where X, y is the coordinate of the current pixel, X does not exceed the wide value range of the current coding block, y does not exceed the high value range of the current coding block, P' (X, y) is the final prediction sample of the pixel (X, y) of the prediction block of the chroma component of the current coding block, P (X, -1) is the reconstructed sample of the pixel adjacent to the upper boundary in the X column, f (y) is the vertical filter coefficient of the pixel (X, y) reference reconstructed sample P (X, -1), and P (X, y) is the original prediction sample of the pixel (X, y).

27. The method according to claim 26, wherein the filter coefficients of the second filter are determined by a look-up table in which filter coefficients are indexed by the size of a prediction block of the chroma component and the distance between pixel (x, y) and pixel (x, -1).

28. The method of claim 16, wherein said predictively modifying the prediction block for the chroma components of the currently decoded block comprises:

analyzing the code stream to obtain a chroma correction flag bit;

determining a value of the chroma correction flag bit to be a first value, the first value indicating that a filter is used for the prediction correction;

performing the prediction correction on a prediction block of a chroma component of the currently decoded block.

29. The method of claim 28, wherein said predictively modifying the prediction block for the chroma components of the currently decoded block comprises:

analyzing the code stream to obtain a chroma correction flag bit;

determining a value of the chroma correction flag bit to be a second value indicating that no filter is used for the prediction correction.

30. The method of claim 28 or 29, wherein the chroma correction flag bit is common to the luma correction flag bit.

31. An image encoding device characterized by comprising:

the dividing unit is used for dividing the image and determining a chroma component intra-frame prediction mode of a current coding block;

a determining unit, configured to determine a prediction block of a chroma component of the current coding block according to the chroma component intra prediction mode;

and the correcting unit is used for correcting the prediction block of the chroma component of the current coding block to obtain the corrected prediction block of the chroma component of the current coding block.

32. An image decoding apparatus, comprising:

the analysis unit is used for analyzing the code stream and determining the chroma component intra-frame prediction mode of the current decoding block;

a determination unit for determining a prediction block of a chroma component of the current decoded block according to the chroma component intra prediction mode;

and the correction unit is used for correcting the prediction block of the chroma component of the current decoding block to obtain the corrected prediction block of the chroma component of the current decoding block.

33. An encoder comprising a non-volatile storage medium and a central processing unit, wherein the non-volatile storage medium stores an executable program, and wherein the central processing unit is coupled to the non-volatile storage medium, and wherein the encoder performs the method of any one of claims 1-15 when the executable program is executed by the central processing unit.

34. A decoder comprising a non-volatile storage medium and a central processor, wherein the non-volatile storage medium stores an executable program, wherein the central processor is coupled to the non-volatile storage medium, wherein the decoder performs the method of any one of claims 16-30 when the executable program is executed by the central processor.

35. A terminal, characterized in that the terminal comprises: one or more processors, memory, and a communication interface; the memory, the communication interface and the one or more processors; the terminal communicating with other devices via the communication interface, the memory for storing computer program code, the computer program code comprising instructions,

the instructions, when executed by the one or more processors, cause the terminal to perform the method of any of claims 1-30.

36. A computer program product comprising instructions for causing a terminal to perform the method according to any one of claims 1-30 when the computer program product is run on the terminal.

37. A computer-readable storage medium comprising instructions that, when executed on a terminal, cause the terminal to perform the method of any one of claims 1-30.

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