JPH06276481A - Picture signal coding and decoding method and recording medium - Google Patents

Abstract

PURPOSE:To improve the coding efficiency by forming a code representing the existence of a non-null conversion coefficient for a color difference signal block separately from a CBP code of the color difference signal block and applying variable length coding to the code together with the CBP code of a luminance signal block. CONSTITUTION:A hybrid coder 12 executes hybrid coding in combination with motion compensation prediction coding and transformation coding such as DCT. A motion compensation prediction error signal S2 of an MB layer outputted from the hybrid coder 12 is subject to variable length coding such as a Huffman code at a VLC device (variable length coder) 13. In this case, the variable length code called the CBP representing whether or not a block in the MB has a non-null DCT coefficient to be sent is added to a header of the MB layer and the resulting code is sent. The CBP is sent so long as any block in the MB has a non-null coefficient. The CBP is formed by a CBP forming device 16 receiving an input of the motion prediction error signal S2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording device and an information reproducing device using storage type moving image media such as optical disks and magnetic tapes. Further, the present invention relates to an information transmission device / reception device suitable for application to, for example, so-called video conference systems, video telephone systems, and broadcasting equipment.

[0002]

2. Description of the Related Art Conventionally, in a so-called video signal transmission system for transmitting a video signal composed of a moving image to a remote place such as a video conference system, a video telephone system, etc. Video signals are encoded using line correlation and inter-frame correlation of
As a result, the transmission efficiency of significant information is improved.

A typical encoding method is MPEG (M
oving Picture Expert Group) 1. MPEG1 is the S of ISO (International Standards Organization) and IEC (International Electrotechnical Commission) JTC (Joint Technical Committee) 1.
C (Sub Committee) 29 WG (Working Group) 11
It is a popular name of the moving picture coding system that has been developed in.
In MPEG1, motion compensation predictive coding and DCT (Discrete
te Cosine Transform) hybrid method is adopted.

For example, the intra-frame coding process uses the line correlation of a video signal, and as shown in FIG.
= T1, t2, t3, ... When transmitting each of the images PC1, PC2PC3, ... Forming a moving image, the image data to be transmitted is one-dimensionally encoded and transmitted within the same scanning line.

In the inter-frame coding process, the adjacent images PC1 and P are successively used by utilizing the inter-frame correlation of the video signal.
The compression ratio is improved by obtaining the image data PC12, PC23 ... Which is the difference in pixel data between C2, PC2, PC3.

As a result, the video signal transmission system high-efficiency-codes the images PC1, PC2, PC3, ... Into digital data having a remarkably small amount of data as compared with the case of transmitting all of the image data, and the transmission line. It can be sent to.

FIG. 2 is a diagram showing how an image sequence is intra / interframe coded. This FIG. 2 is one unit of encoding in the cycle of 15 frames.

Since the frame 2 is intra-frame coded, it is called Intra Picture.

Frames 5, 8, 11, and 14 are called "Predicted Picture" because they are predicted only from the forward direction and inter-frame coded.

Further, frames 0, 1, 3, 4, 6,
7, 9, 10, 12, and 13 are called bidirectional pictures because they are predicted only from the forward direction, from the backward direction, and from both directions and are inter-frame coded.

As shown in FIG. 3, the moving picture coding apparatus converts an input video signal VD into a luminance signal and a color difference signal through a preprocessing circuit, and then converts it into an 8-bit digital signal by an analog-digital conversion circuit. , Convert from frame format to block format and input to encoder.

The image data sequentially sent as input image data to the encoder is converted from frame image data into a block format. The image data in this block format is input to an encoder, and the encoder performs high-efficiency compression encoding of the image to generate a bitstream.

This bit stream is transmitted to the decoder via communication or recording media. The decoder outputs block format data from the bitstream, converts this data to frame format,
An output image is generated through digital-analog conversion.

One frame image data (picture)
Is divided into N slices, as shown in Figure 4,
Each slice includes M macro blocks, and each macro block includes color difference signal data Cb and Cr which are color difference signal data corresponding to all pixel data of luminance signal data Y1 to Y4 for 8 × 8 pixels. It consists of

At this time, the arrangement of the image data in the slice is such that the image data is continuous in units of macroblocks, and in this macroblock, the image data is continuous in units of small blocks in the order of raster scanning. Has been done.

Here, the macroblock uses image data of 16 × 16 pixels continuous in the horizontal and vertical scanning directions as one unit in four blocks Y1 to Y4 with respect to the luminance signal. In the two corresponding color difference signals, the data amount may be reduced and then time-axis multiplexed. For example, in MPEG1, since the image signal format is a 4: 2: 0 component signal, as shown in FIG. 5, each one minute block Cr,
Data for 16 × 16 pixels is assigned to Cb.

On the other hand, MPEG2 received after MPEG1
, The image signal to be encoded is 4: 2: 0.
Not only the component signals, but also 4: 2: 2 component signals and 4: 4: 4 component signals are being studied.

In FIGS. 6 and 7, 4: 2: 2 and 4: 2: 2.
The relationship between macroblocks and blocks in each case of a 4: 4 component signal is shown. In the 4: 2: 2 component signal, one minute block Cr or C is used.
Data of 16 × 8 pixels is assigned to b.
In the 4: 4: 4 component signal, four blocks are assigned to the color difference signal as in the case of the luminance signal.

In the encoder, processing is performed in macroblock units. FIG. 8 shows a block diagram of the MPEG encoder.

The motion vector detection circuit detects the motion vector of the input block format image. As already described with reference to FIG. 2, the motion vector detection circuit uses the non-interpolated frame as a predicted image to generate an interpolated image using motion detection.

Therefore, in order to hold the predicted image for detecting the motion, the forward original image and the backward original image are held and the motion vector is detected between the current reference image.
Here, in the detection of a motion vector, the motion vector is the one in which the sum of absolute values of inter-frame differences in block units is the smallest.

The sum of absolute values of inter-frame differences in block units is sent to the intra-frame / forward / bidirectional prediction decision circuit. The intra-frame / forward / bidirectional prediction determination circuit determines the prediction mode of the reference block based on this value.

Based on this prediction mode, intraframe / forward / bidirectional prediction is switched in block units, and the input image itself is selected in the intraframe coding mode, and the respective predictions are calculated in the forward / bidirectional prediction mode. Inter-frame coded data from an image is generated, and the difference data is sent to a discrete cosine transform (DCT) through a switching circuit.
(Discrete cosine transform)) is output to the circuit.

The DCT circuit utilizes the two-dimensional correlation of the video signal to perform discrete cosine transform on the input image data or the difference data in block units, and outputs the resulting transformed data to the quantizing circuit. .

The quantizing circuit quantizes the DCT transform data with a quantizing step size determined for each macroblock and slice, and quantizes the quantized data obtained at the output end as a result of variable length coding (VLC (variable length code)). And the inverse quantization circuit. The quantization scale used for the quantization is determined by feeding back the buffer remaining amount of the transmission buffer, so that the transmission buffer is not broken. This quantization scale is also supplied to the variable length coding circuit and the dequantization circuit together with the quantized data.

When transmitting quantized data, a variable length code (VLC, Variable Length Code) called CBP (Coded Block Pattern) indicating whether or not each block in a macroblock has a non-zero DCT coefficient to be transmitted. ) To MB
It is added to the layer header and transmitted. CBP exists if even one block in the MB has a non-zero coefficient.

FIG. 9 shows a VLC table for a CBP code when an image to be coded is a 4: 2: 0 component signal. This table is also used in MPEG1, and there are non-zero coefficients for each block in the order of Y0, Y1, Y2, Y3, Cb, and Cr '1',
As a value of “0”, a value obtained by arranging MSB (Most Significant Bit) and displaying the binary number is a CBP value, and a VLC code corresponding to each value is given.

In decoding, VLC is 2 as shown in FIG.
Converted to decimal notation, MSB displays Y0, Y1, Y2, Y3, Cb, C
It means that there is a non-zero coefficient in the block that becomes "1" in the order of r. For example, the shortest VLC code "111" indicates that the non-zero coefficient exists only in the Y0, Y1, Y2, and Y3 blocks (the non-zero coefficient does not exist in the Cb and Cr blocks). . In the CLC VLC table structure for a 4: 2: 0 component signal in MPEG1, a short VLC is assigned when a non-zero coefficient does not exist in a color difference signal block (Cb, Cr block).

When the image to be encoded is a 4: 2: 2 component signal, as shown in FIG. 10, first, Y0, Y1, Y2,
In the block order of Y3, Cb0, Cr0, whether or not there is a non-zero coefficient for each block is variable length coded as in the case of the 4: 2: 0 component signal, and then two blocks of Cb1, Cr1 are added. With respect to, a 2-bit fixed length code (FLC, Fixed Length Code) is transmitted with a non-zero coefficient of "1" and non-zero coefficient of "0". As a result, the CBP can be transmitted with the code length of the VLC code + 2 bits.

When the image to be encoded is a 4: 4: 4 component signal, as shown in FIG. 11, first, Y0, Y1, Y2,
In the block order of Y3, Cb0 and Cr0, whether or not there is a non-zero coefficient for each block is variable length coded as in the case of the 4: 2: 0 component signal, and then C
There are non-zero coefficients for the two blocks b1 and Cr1.
A 2-bit fixed-length code is transmitted with 1'and none '0'. Further, a 2-bit fixed length code is similarly transmitted for Cb2 and Cr2, and a 2-bit fixed length code is similarly transmitted for Cb3 and Cr3. As a result, the CBP can be transmitted with the code length of the VLC code + 6 bits.

The variable length coding circuit that receives the quantized data receives the quantized data from the quantization scale, prediction mode,
Variable length coding processing with motion vectors, CBP, etc.,
It is supplied to the transmission buffer memory as transmission data.

The transmission buffer memory temporarily stores the transmission data in the memory and then outputs it as a bit stream at a predetermined timing, and at the same time, outputs a quantization control signal in macroblock units according to the residual data amount remaining in the memory. It is designed to feed back to the quantization circuit to control the quantization scale. As a result, the transmission buffer memory adjusts the amount of data generated as a bitstream, and maintains the appropriate amount of data (the amount of data that does not cause overflow or underflow) in the memory.

Incidentally, when the remaining amount of data in the transmission buffer memory increases up to the allowable upper limit, the transmission buffer memory increases the quantization scale of the quantizing circuit in accordance with the quantization control signal, so that the data amount of the quantized data is increased. Lower.

On the contrary, when the remaining amount of data in the transmission buffer memory is reduced to the allowable lower limit value, the transmission buffer memory reduces the quantization scale of the quantization circuit by the quantization control signal, thereby performing quantization. Increase the amount of data.

The inverse quantization circuit inversely quantizes the quantized data sent from the quantization circuit into a representative value, converts the quantized data into inverse quantized data, and decodes the converted data of the output data before conversion in the quantization circuit. , Inverse quantized data is transformed into discrete cosine traverse IDCT (inverse discrete cosine tras)
form) is supplied to the circuit.

The IDCT circuit converts the dequantized data decoded by the dequantization circuit into decoded image data by a conversion process reverse to that of the DCT circuit, and outputs the decoded image data to the motion compensation circuit.

The motion compensation circuit performs local decoding based on the output data of the IDCT circuit, the prediction mode and the motion vector, and writes the decoded image as a forward prediction image or a backward prediction image in the frame memory. In the case of forward / bidirectional prediction, the difference from the predicted image is sent as the output of the IDCT circuit, so by adding this difference to the predicted image,
Local decoding is performed.

This predicted image is exactly the same as the image decoded by the decoder, and the next processed image performs forward / bidirectional prediction based on this predicted image.

FIG. 12 shows a block diagram of the decoder. The bitstream is input to the decoder via the transmission medium. This bit stream is input to a variable length decoding (IVLC) circuit via a reception buffer. The variable length decoding circuit decodes the quantized data, the motion vector, the prediction mode, the quantization scale, the CBP, etc. from the bit stream. The quantized data and the quantization scale are input to the next inverse quantization circuit.

The operations of the inverse quantization circuit, the IDCT circuit, and the motion compensation circuit are as described in the description of the encoder in FIG.

The motion compensation circuit performs decoding based on the output data of the IDCT circuit, the prediction mode, and the motion vector, and writes the decoded image as a forward prediction image or a backward prediction image in the frame memory. This predicted image is exactly the same as the image locally decoded by the encoder, and the next decoded image is decoded in the forward / bidirectional directions based on this predicted image.

[0042]

[Problems to be Solved by the Invention] 4: 2: 2 and 4: 4:
When a CBP code is encoded for a moving image of four component signals, for example, in FIG. 10, Y0, Y1, Y
Consider a case where all the blocks of 2, Y3, Cb0 and Cr0 do not have non-zero coefficients and one of the two blocks of Cb1 and Cr1 has non-zero coefficients.

In the above encoding method, it is necessary to encode CBP because Cb1 and Cr1 have non-zero coefficients.
The CBP value composed of Y0, Y1, Y2, Y3, Cb0 and Cr0 blocks is '000000' and there is no corresponding VLC code. Therefore, it becomes necessary to add a new VLC code to the VLC table for CBP, and the compatibility with MPEG1 deteriorates.

Generally, when the component image signal is encoded by the hybrid encoding method, the motion compensation prediction error signal in the macroblock has non-zero coefficients only in the luminance signal block (Y block) and the chrominance signal block (Cb , Cr block) often has no non-zero coefficient.

Therefore, the conventional method of adding a fixed length code of 2 bits for a 4: 2: 2 component signal and a 6 bit for a 4: 4: 4 component signal is sufficient for the color difference signal. Coding efficiency cannot be expected.

[0046]

In order to solve such a problem, the image signal coding method according to the present invention divides one screen of an input image signal into macroblocks composed of a plurality of pixels, and the respective macroblocks are divided into macroblocks. A predetermined conversion for compression processing in units of, and a CBP code for expressing in which of the small blocks further dividing the macro block the non-zero conversion coefficient exists during variable length encoding, In the image signal encoding method of transmitting compressed data by adding to the header of the macro block, a code indicating the presence or absence of a non-zero conversion coefficient is provided for the color difference signal block separately from the CBP code of the color difference signal block. It is characterized in that it is configured and variable length coding is performed together with the CBP code of the luminance signal block.

Further, in the image signal decoding method according to the present invention, the image signal encoded in macroblock units formed by dividing one screen into a plurality of parts is subjected to inverse VLC to further compress the compressed image signal and the macroblock. The CBP code for representing in which of the divided small blocks the non-zero transform coefficient exists is separated, this CBP code is decoded, and the decoded CB
In the image signal decoding method for decoding the compressed image signal based on a P code, the decoded CBP code includes a CBP code for a luminance signal block, a CBP code for a color difference signal block, and a color difference signal block. And a code indicating the presence / absence of non-zero conversion coefficient for the color difference signal block, which is configured separately from the CBP code.

[0048]

In the prior art, the CB for performing VLC is first of all used.
Since the P value is composed of the blocks Y0, Y1, Y2, Y3, Cb0, and Cr0, for example, in a 4: 2: 2 component signal, there is no non-zero coefficient in these 6 blocks,
It was necessary to prepare a new VLC code for the case where there are non-zero coefficients in the remaining Cb1 and Cr1 blocks, but in the present invention, Y0, Y1, Y2, Y3, Cb ', Cr'. , All of them are '0', it means that there is no non-zero coefficient in all the macroblocks in the macroblock, and it is not necessary to send the CBP itself. Therefore CB
As the VLC table for P, the one used in MPEG1 can be used as it is without change.

Further, conventionally, even if there is no non-zero coefficient in the color difference signal block, after performing VLC, 4: 4:
In the case of encoding a 2: 2 component signal, it is always necessary to add a 2-bit code in the case of encoding a 4: 4: 4 component signal, but in the present invention, it is necessary to add a 6-bit code to the color difference signal block. If there are no non-zero coefficients, only VLC need be performed and no additional bits are needed.

[0050]

Embodiments (1) Encoding Device (Encoder) An embodiment of a moving image encoding device having a CBP encoding means of the present invention will be described with reference to FIG.

In this encoding apparatus, the input image is shown in FIG.
Encoding is performed based on the data structure in MPEG1 as shown in FIG. Each data layer will be briefly described below.

1. Block Layer The block is composed of, for example, 8 lines × 8 pixels adjacent to each other in luminance or color difference. For example, DCT (Discrete C
(osine Transform) is executed in this unit.

2. MB (Macro Block) Layer The block structure of the MB is as shown in FIGS. 5, 6 and 7. What is used for the motion compensation mode, whether the prediction error need not be sent, and the like are determined in this unit.

3. The slice layer image is composed of one or a plurality of macroblocks that are arranged in the scanning order. At the beginning of the slice, the first macroblock contains data indicating its position in the image, and is designed to be able to recover if an error occurs.
Therefore, the length and starting position of the slice are arbitrary and can be changed depending on the error condition of the transmission path.

4. PICTURE LAYER A picture or each image is composed of at least one or more slices. Then, it is classified into I-picture, P-picture and B-picture according to the encoding method.

5. GOP layer A GOP is composed of one or more I-pictures and zero or more non-I-pictures.

6. Video sequence layer A video sequence is composed of one or more GOPs having the same image size, image rate and the like.

Information for controlling the basic operation of the present encoding device is stored in the memory 18. These are the image frame size, the output bit rate of encoded information, the motion prediction compensation method, and the like. These pieces of information are output as S25.

The moving image to be encoded is the image input terminal 10
Will be entered more. The input image signal is supplied to the field memory group 11. Field memory group 11
From the macroblock signal S1 currently being encoded,
It is supplied to the hybrid encoder 12.

The hybrid encoder 12 is a hybrid code combining motion compensation predictive coding, which is a typical high-efficiency coding method for moving images, and transform coding such as DCT (Discrete Cosine Transform). Make a change. Since the structure does not affect the main point of the present invention, the description thereof is omitted here.

The MB layer motion compensation prediction error signal S2 output from the hybrid encoder 12 is variable length encoded into a Huffman code or the like by the VLC unit (variable length encoder) 13. At this time, a CBP (Coded B) indicating whether or not the block in the MB has a non-zero DCT coefficient to be transmitted.
A variable length code called a lock pattern) is added to the MB layer header and transmitted. The CBP is transmitted if even one block in the MB has a non-zero coefficient. The CBP receives the input of the motion compensation prediction error signal S2 and is configured by the CBP configurator 16. The algorithm used to form the CBP is shown in FIG. 14 by taking the case where the image signal is a 4: 2: 2 component signal as an example.

The CBP configurator 16 first checks whether or not each of the color difference signal blocks Cb and Cr in the macroblock has a non-zero coefficient. The number of blocks to be examined varies depending on the image signal, one for a 4: 2: 0 component signal, two for a 4: 2: 2 component signal, and four for a 4: 4: 4 component signal. Become. These information bits are Cb 'and C, respectively.
r'and '0' if all blocks have non-zero coefficients
If there is a non-zero coefficient in one or more blocks, set to '1'.

When Cb 'is'1' and the image signal is a 4: 2: 2 component signal, a 2-bit codeword Cbext is obtained from the information of which of the two blocks of Cb has a non-zero coefficient. Constitute.

If Cb 'is'1' and the image signal is a 4: 4: 4 component signal, a 4-bit codeword is obtained from the information of which of the four blocks of Cb has a non-zero coefficient. Configure Cbext. Crext is constructed in the same manner as Crext. This codeword C
The bext and Crext are composed of fixed length (FLC).

Next, it is determined whether or not there are non-zero coefficients in the four luminance signal blocks in the macro block by the 4-bit information Y0.
Represented by Y1Y2Y3, a 6-bit bit string is constructed with Cb 'and Cr', and variable length coding is performed with reference to the VLC table in FIG.

The image signal is 4: 2: 2 or 4: 4: 4
If it is a component signal, the CBP composer 16
After variable length coding Y0Y1Y2Y3Cb 'Cr', C
The value of b'is checked, and if '1' is set, Cbext that has already been constructed is added after this variable length code. The number of bits to be added is 2 bits when the image signal is a 4: 2: 2 component signal and 4 bits when the image signal is a 4: 4: 4 component signal. In addition, check the value of Cr 'and set it to' 1 '
If is set, then Crext is similarly added after this variable length code. When the image signal is a 4: 2: 0 component signal, Cb 'and Cr' represent whether or not each color difference signal block of Cb and Cr has a non-zero coefficient, so only this variable length coding is required. .

The CBP structuring device 16 is as described above.
Configure CBP.

This construction method utilizes the fact that the tendency that non-zero coefficients exist in each block of Cb and Cr is biased. In general, Cb and Cr blocks often do not have non-zero coefficients. In this case, Cbext and Crext
Therefore, it is possible to code CBP very efficiently without the need to add. However, even if any block of Cb and Cr has a non-zero coefficient, its existence is still biased.

For example, when the image signal is a 4: 2: 2 component signal, both of the two blocks Cb and Cr have nonzero coefficients, rather than only one of them. There is a higher proportion.

Therefore, as another method, in order to perform more efficient encoding, the variable length encoding is performed in consideration of where each non-zero coefficient is likely to appear in each block of Cb and Cr. Can be considered. VLC for additional bit when image signal is 4: 2: 2 component signal
FIG. 15 shows the table, and FIG. 16 shows the VLC table for additional bits when the component signal is 4: 4: 4.
, Respectively.

In this method, when adding Cbext and Crext to CBP, the code is not added as it is, but
The code is variable length coded and added with reference to FIGS.

The variable-length code output from the VLC unit 13 is stored in the buffer memory 14 and then output to the output terminal 15.
The bit stream is transmitted at a constant transmission rate.

The data structure of this transmitted bit stream is as shown in FIG.

Here, the CBP code is added to the macroblock header together with the motion vector, the prediction mode, the MC mode, the DCT mode and the like.

The bit stream output from the transmission buffer memory is multiplexed with the coded audio signal, sync signal, etc., further, an error correction code is added, and a predetermined modulation is applied to the bit stream. It is recorded as an uneven pit on the master disk through light. A stamper is formed using this master disk, and a large number of duplicate disks (for example, optical disks) are formed by the stamper. Of course ISDN,
It may be transmitted to a transmission line such as satellite communication.

(2) Decoding Device (Decoder) A moving image decoding device corresponding to the above moving image coding device will be described with reference to FIG.

The bit stream signal input from the input terminal 50 is stored in the buffer memory 51 and then supplied to the inverse VLC unit 52. As described in the description of the encoding device, the bit stream has six layers, that is, a video sequence, a GOP, a picture,
It consists of slices, macroblocks, and block layers. The video sequence, GOP, picture, and slice layers receive a start code indicating that they start at the beginning of each layer, and then receive header information that controls the decoding of the image.

Upon receiving each start code, the inverse VLC unit 52 decodes the header information of each layer and stores the obtained control information for image decoding in the memory 201. These pieces of information are output as S104.

The MB layer motion compensation prediction error signal S80 supplied from the inverse VLC unit is supplied to the hybrid decoder 53. The hybrid decoder 53 performs hybrid decoding that combines motion compensation, which is a typical high-efficiency coding method for moving images, and transform coding such as inverse DCT (Invers Discrete Cosine Transform). Since the structure does not affect the main point of the present invention, the description thereof is omitted here.

At this time, VLC of CBP indicating which block in the MB has a non-zero DCT coefficient
Is received in the header of the MB layer, and the CBP decoder 54
Will be decrypted with. The algorithm used for decoding is shown in FIG. 19 by taking the case where the image signal is in the 4: 2: 2 format as an example.

The CBP code is first inverse VLC-converted into a 6-bit code using the VLC table. This in turn
Let Y0, Y1, Y2, Y3, Cb ', Cr'. The structure of the luminance signal block of the macro block is 4: 2: 0, 4: 2:
The component image signals of 2, 4: 4: 4 are all the same, and CBP is (Y0, Y1, Y2, Y3).
That is, there is a non-zero coefficient in the block that becomes "1" in the block order.

When the image signal is a 4: 2: 0 component signal, Cb 'and Cr' represent whether or not each block of Cb and Cr has a non-zero coefficient as it is. It has been decrypted.

When the image signal is a 4: 2: 2 component signal, the CBP decoder first determines that Cb 'is "1".
If it is '1', the bit stream is further 2 bits for FLC and 1-2 for VLC.
Read the bit information and set it in Cb0 and Cb1. On the other hand, if Cb 'is'0', reading is not performed and both Cb0 and Cb1 are set to '0'. The same processing is performed for Cr 'to obtain Cr0 and Cr1. Thus, Y0, Y1, Y2, Y3, Cb0, Cb1, Cr0 and Cr1 which are CBP information of the 4: 2: 2 component signal are decoded.

When the image signal is a 4: 4: 4 component signal, the CBP decoder firstly sets Cb 'to "1".
Check if it is '1' and read 4 bits of information from the bitstream, and read this as Cb0, Cb1, C
Set to b2 and Cb3.

When Cb 'is'0', reading is not performed and Cb0, Cb1, Cb2 and Cb3 are all set to '0'. The same processing is performed for Cr 'to obtain Cr0, Cr1, Cr2, Cr3.

In this way, Y0, Y1, Y2, Y3, Cb0, Cb1, which is the CBP information of the 4: 4: 4 component signal.
Cb2, Cb3, Cr0, Cr1, Cr2, Cr3 are decoded.

Here, in the image signal decoding method for variable length decoding the CBP code of the color difference signal, the image signal is a 4: 2: 2 or 4: 4: 4 component signal and Cb 'and Cr' are If it is '1', then the data read from the bit stream is changed to that shown in FIG.
VLC table for component signals) or Figure 1
Inverse VLC is performed while referring to 6 (VLC table for 4: 4: 4 component signals) to obtain information on which block of the block group of Cb and Cr has a non-zero coefficient.

The CBP code is decoded as described above.

Then, the decoded macroblock layer data S81 based on the CBP code is output from the terminal 55. As described above, the image data is decoded from the bitstream data.

[0090]

According to the image signal encoding method of the present invention, CB
When constructing a P code, the VLC table used for variable length coding Y0, Y1, Y2, Y3, Cb ', Cr' is MPE.
The same VLC table of G1 can be used, and the consistency is good.

Further, the image signal coding method according to the present invention generally utilizes the property that when the component image signal is coded by the hybrid coding method, the color difference signal block often does not have a non-zero coefficient. Therefore, good coding efficiency can be obtained when CBP is coded.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of high efficiency encoding.

FIG. 2 is a diagram showing a GOP structure of an image sequence.

FIG. 3 is a diagram showing a schematic configuration of a moving image encoding / decoding device.

FIG. 4 is a diagram showing a structure of moving image data.

FIG. 5 is a block configuration diagram of an MB with a 4: 2: 0 component signal.

FIG. 6 is a block diagram of an MB with a 4: 2: 2 component signal.

FIG. 7 is a block diagram of an MB with a 4: 4: 4 component signal.

FIG. 8 is a block diagram of an MPEG encoder.

FIG. 9 is a VLC table of CBP code in MPEG1.

FIG. 10 is a diagram for explaining a method of configuring a CBP code (when the signal is 4: 2: 2) in the conventional invention.

FIG. 11 is a diagram for explaining a method of configuring a CBP code (when the signal is 4: 4: 4) in the conventional invention.

FIG. 12 is a block diagram of an MPEG decoder.

FIG. 13 is a block diagram of an encoder according to the present invention.

FIG. 14 is an algorithm for constructing a CBP code according to the present invention.

FIG. 15 is a VLC table (when the signal is 4: 2: 2) applied to the additional bits for the color difference signal block of the CBP code.

FIG. 16 is a VLC table (when the signal is 4: 4: 4) applied to the additional bits for the color difference signal block of the CBP code.

FIG. 17 is a diagram showing a structure of moving image data according to the present invention.

FIG. 18 is a block diagram of a decoder according to the present invention.

FIG. 19 is an algorithm for decoding a CBP code according to the present invention.

Claims (15)

[Claims] 1. A screen of an input image signal is divided into macroblocks composed of a plurality of pixels, a predetermined conversion for compression processing is performed in units of each macroblock, and at the time of variable length coding, the macro In the image signal coding method, a CBP code for representing in which of the small blocks the block is further divided, a non-zero transform coefficient exists, is added to the header of the macro block, and compressed data is transmitted. An image signal code characterized in that a code indicating the presence / absence of a non-zero conversion coefficient is configured separately from the CBP code of the color difference signal block for the color difference signal block, and is variable-length coded together with the CBP code of the luminance signal block. Method. 2. The image signal coding method according to claim 1, wherein the code indicating the presence or absence of the non-zero transform coefficient is composed of 2 bits. 3. The image signal coding method according to claim 1, wherein the CBP code of the color difference signal block is fixed-length coded. 4. The image signal encoding method according to claim 2, wherein when the input image signal is a component image signal of (4: 2: 0) format, the CBP code of the color difference signal block is converted by the code of 2 bits. An image signal encoding method characterized by being configured. 5. The image signal encoding method according to claim 3, wherein when the input image signal is a component image signal of (4: 2: 2) format, the non-zero transform coefficient is present by the code of 2 bits. CB of the color difference signal block only when the non-zero conversion coefficient is present.
An image signal coding method, wherein the P code is composed of 4 bits. 6. The image signal encoding method according to claim 3, wherein when the input image signal is a component image signal of (4: 4: 4) format, the existence of the non-zero transform coefficient is caused by the code of 2 bits. And the CBP code of the color difference signal block is set to 8 only when there is a conversion coefficient.
An image signal encoding method characterized by comprising bits. 7. The image signal coding method according to claim 1, wherein the CBP code of the color difference signal block is variable length coded. 8. A screen of an input image signal is divided into macroblocks composed of a plurality of pixels, and each macroblock is subjected to a predetermined conversion for compression processing. This is an image signal coding method in which a CBP code for indicating in which of the small blocks the block is further divided into has a non-zero transform coefficient is added to the header of the macro block and compressed data is transmitted. Then, in the color difference signal block, a code indicating the presence or absence of a non-zero conversion coefficient is configured separately from the CBP code of the color difference signal block, and variable length coding is performed together with the CBP code of the luminance signal block. A recording medium that records data generated by the. 9. An inverse VLC of an image signal encoded in units of macroblocks, which is formed by dividing one screen into a plurality of blocks, to obtain a non-zero value in any of the small blocks obtained by further dividing the compressed image signal and the macroblock. In the image signal decoding method, a CBP code for indicating whether a transform coefficient is present is separated, the CBP code is decoded, and the compressed image signal is decoded based on the decoded CBP code. The CBP code is configured separately from the CBP code for the luminance signal block, the CBP code for the color difference signal block, and the CBP code for the color difference signal block, and whether there is a non-zero conversion coefficient for the color difference signal block. And an image signal decoding method. 10. The image signal decoding method according to claim 9, wherein the code indicating the presence or absence of the non-zero transform coefficient after decoding is composed of 2 bits. Method. 11. The image signal decoding method according to claim 9, wherein the CBP code of the color difference signal block is fixed-length decoded. 12. The image signal decoding method according to claim 10, wherein when the image signal is a component image signal of (4: 2: 0) format, the CBP code of the color difference signal block is converted by the code of 2 bits. An image signal decoding method characterized by being configured. 13. The image signal decoding method according to claim 11, wherein when the image signal is a component image signal of (4: 2: 2) format, the CBP code after decoding uses the two-bit code The presence or absence of the conversion coefficient of zero is indicated, and the CBP code of the color difference signal block is configured with a fixed length of 4 bits only when the conversion coefficient of non-zero is present. Method. 14. The image signal decoding method according to claim 11, wherein when the image signal is a component image signal of (4: 4: 4) format, the CBP code after decoding is non-zero by the code of 2 bits. The presence / absence of the transform coefficient is indicated, and the CBP code of the color difference signal block is constituted by 8 bits only when the non-zero transform coefficient is present. 15. The image signal decoding method according to claim 9, wherein the CBP code of the color difference signal block is variable length decoded.