CN101267559A - General entropy decoding method and device for video decoder - Google Patents

Abstract

The invention discloses a universal entropy decoding method and a universal entropy decoding device for a video decoder, belonging to the field of multimedia digital signal processing. The entropy decoding method recombines video decoding calculation into bit decoding, syntactic element decoding and entropy decoding control three parts, in accordance with the similarity relation between entropy decodings in video decoding. The entropy decoding device in the video decoder comprises a bit decoding module, a syntactic element decoding module, a control module, and a memory. In the method, calculation in each step has similar calculating granularity and data local characteristic, which is helpful to distributing calculating resources reasonably, simplifying the internal interfaces of the universal entropy decoding device in the video decoder, and improving the entropy decoding efficiency in video decoding.

Description

General entropy decoding method and device for video decoder

technical field

The invention relates to a method and device in the field of multimedia digital signal processing, in particular to a general entropy decoding method and device for a video decoder.

Background technique

At present, the latest video codec technology includes MPEG-x series, H.26x series and China's AVS standard, among which entropy coding technology adopts variable length coding technology and context-based adaptive variable length coding technology (CAVLC: Context- based Adaptive Variable Length Coding) and context-based arithmetic coding technology (CABAC: Context-based Adaptive Binary Arithmetic Coding), thus achieving a high data compression rate.

After searching the literature of the prior art, it is found that the patent number is 200410093097.1, and the patent name is "Single Clock Cycle Variable Length Entropy Decoding Device". In this patent, the codewords read from the outside are first sent to the FIFO buffer for buffering. The output port of the FIFO buffer is a whole word wide, and the read signal of the FIFO buffer is controlled by the carry signal of the length accumulator, and the output of the FIFO buffer is sent to the first-stage barrel shift register for latching. Accumulate and shift under control, the shift output signal is sent to the second-stage barrel shift register, and the shift of the second-stage barrel shift register is controlled by the length of the current decoding symbol, and is processed by the two-stage barrel shift register The final data is sent to the hardware table look-up unit through the internal interconnection bus, and the result of a working sub-table is selected as output through the strobe. The limitation of this patent is that it can only perform variable-length entropy decoding, and cannot adapt to the latest video codec counts, such as context-based arithmetic coding technology.

Contents of the invention

The present invention aims at the deficiencies of the above-mentioned prior art, and provides a general entropy decoding method and device for a video decoder, which reorganizes video entropy decoding into three steps of bit decoding, syntax element decoding, and entropy decoding control. The operations in each step have similar properties, which is conducive to rationally allocating computing resources and improving the efficiency of video entropy decoding.

The present invention is achieved through the following technical solutions.

The invention provides a general entropy decoding method of a video decoder, comprising the following steps:

Step 1, input a segment of compressed video bitstream, determine the entropy decoding mode applied to the bitstream according to the video compression standard followed by the bitstream, and obtain context parameters;

The entropy decoding mode refers to the mode for entropy decoding in each video standard, including arithmetic decoding mode, fixed-length decoding mode and variable-length decoding mode, and variable-length decoding mode is divided into signed exponent Columbus decoding, unsigned exponent Columbus decoding, first-order to third-order exponential Columbus decoding, truncated exponential Columbus decoding, special syntax element look-up table, etc.

The context parameter refers to the syntax element information of the decoded adjacent blocks required for decoding in context-based adaptive variable-length decoding or context-based arithmetic decoding.

Step 2, if the entropy decoding mode is arithmetic decoding, perform arithmetic decoding according to the entropy decoding mode and context parameters in step 1, obtain the bits after arithmetic decoding and output them; if the entropy decoding mode is fixed-length decoding or variable-length decoding, directly Output raw bits.

Step 3, according to the entropy decoding mode and context parameters obtained in the first step, and the bits obtained in the second step, perform syntax element decoding, and loop through steps 2 and 3 until a syntax element is completed and output after decoding, and Record syntax element information required for subsequent entropy decoding;

The syntax element information refers to the information corresponding to the codeword in the bit stream, which can be obtained by entropy decoding methods such as fixed-length decoding, variable-length decoding and context-based decoding.

Step 4: Repeat the above step 1 to step 3 until the decoding of all input bit streams is completed.

The present invention also provides a general entropy decoding device in a video decoder, comprising: a bit decoding module, a syntax element decoding module, a control module, and a memory, wherein:

Input the bit stream in the bit decoding module, and receive entropy decoding mode information and context parameters from the control module;

In the arithmetic decoding mode, perform bit decoding in arithmetic decoding, bit decoding is to select a table lookup table according to the context parameter, and decode a bit according to the input bit stream, and output the processed bit to the syntax element decoding module;

In the fixed-length decoding or variable-length decoding mode, the input bit stream is directly output to the syntax element decoding module.

The syntax element decoding module accepts the bits output by the bit decoding module and the entropy decoding mode and context parameters in the control module, performs syntax element decoding, and transmits the decoded syntax element information to the control module;

The control module receives the syntax element information output by the syntax element decoding module, stores the syntax elements that will be used in the subsequent context-based entropy decoding into the memory, and obtains the syntax elements of adjacent macroblocks required for decoding the next syntax element from the memory, Calculate the context parameters according to the MPEG-x series, H.26x series or China's AVS standard, and get the entropy decoding mode of the next syntax element; then output the entropy decoding mode of the next syntax element and the required context parameters to the bit a decoding module and a syntax element decoding module;

Syntax elements that will be used in subsequent context-based entropy decoding stored by the control module are stored in the memory.

The syntax element decoding module decodes the bits output by the bit decoding module into syntax elements according to the entropy decoding mode and context parameters output by the control module, and the decoding mode includes fixed-length decoding, signed exponential Golomb decoding, unsigned exponential Golomb decoding, First-order to third-order exponential Golomb decoding, truncated exponential Golomb decoding, special syntax element look-up table, etc.

Compared with the prior art, the present invention has the following beneficial effects: according to the similarity relationship between various entropy decoding in video decoding, the present invention reorganizes video decoding operations into bit decoding, syntax element decoding, entropy decoding control (including context Parameter storage and reading) three steps, and according to the corresponding devices provided by the three steps, the calculations in each step have similar calculation granularity and data local characteristics, which is beneficial to rationally allocate computing resources and simplify video processing. The internal interface of the general-purpose entropy decoding device in the decoder improves the efficiency of entropy decoding in video decoding. The average number of decoded bits per clock cycle in the arithmetic entropy decoding mode reaches more than 0.66, and the number of decoded bits per clock cycle in the variable-length entropy decoding mode reaches 0.72 or more.

Description of drawings

Fig. 1 is the flowchart of entropy decoding method of the present invention;

Fig. 2 is a structural block diagram of an entropy decoding device of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings: this embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following the described embodiment.

This embodiment is based on the H.264 standard reference specification (MAIN PROFILE).

As shown in Figure 1, this embodiment provides a general entropy decoding method in video decoding, including the following steps:

Step 1, input a section of video bit stream, and decide which entropy decoding mode to apply to it according to the video compression standard followed by the bit stream. In this embodiment, the entropy decoding mode is arithmetic decoding, and context parameters are obtained at the same time;

The entropy decoding mode refers to different modes for entropy decoding in different video standards, including arithmetic decoding mode, fixed-length decoding mode and variable-length decoding mode, and variable-length decoding mode is divided into signed exponential Columbus decoding, unsigned Exponential Golomb decoding, first-order to third-order exponential Golomb decoding, truncated exponential Golomb decoding, special syntax element lookup table, etc. In this embodiment, a context-based arithmetic decoding technology (CABAC: Context-based Adaptive Binary Arithmetic Coding) is selected with context parameters.

The context parameter refers to syntax element information of decoded adjacent blocks required for entropy decoding in context-based adaptive variable-length decoding or context-based arithmetic decoding. In this embodiment, it is the syntax element information of the decoded adjacent blocks required for entropy decoding, including macroblock type (MB TYPE), 8x8 block decoding information (TRANSFORM SIZE 8X8 FLAG), field decoding information (MB FIELD DECODING FLAG) , Macroblock skip information (MB SKIP FLAG), block amplitude existence information (CODED BLOCK PATTERN & CODEDBLOCK FLAG), motion vector residual (MVD) and reference index (REF INDEX) and other macroblock levels and syntax elements below the macroblock level information.

Step 2: Arithmetic decoding is performed according to the entropy decoding mode and context parameters in the first step, and bits after arithmetic decoding are obtained and output.

Step 3, according to the entropy decoding mode and context parameters obtained in the first step, and the bits obtained in the second step, perform syntax element decoding, and loop through steps 2 and 3 until a syntax element is decoded and output, and Record syntax element information required for subsequent entropy decoding.

The syntax element information refers to the information corresponding to the codeword in the bit stream, which can be obtained by entropy decoding methods such as fixed-length decoding, variable-length decoding and context-based decoding. In this embodiment, the syntax elements include macroblock type (MB TYPE), 8x8 block decoding information (TRANSFORM SIZE 8X8 FLAG), field decoding information (MB FIELD DECODING FLAG), macroblock skip information (MB SKIP FLAG), amplitude Information (RUN-LEVEL), motion vector residual (MVD) and reference index (REF INDEX) and other macroblock level and syntax element information below the macroblock level.

Step 4: Repeat the above step 1 to step 3 until the decoding of all input bit streams is completed.

As shown in Figure 2, the general entropy decoding device in the video decoder involved in this embodiment includes: a bit decoding module, a syntax element decoding module, a control module, and a memory, wherein:

The bit stream is input into the bit decoding module, and the entropy decoding mode information and context parameters of the control module are accepted. In the arithmetic decoding mode, the bit decoding in the arithmetic decoding is performed, and the bit decoding is to select a table lookup table according to the entropy decoding mode information and context parameters, and decode a bit according to the input bit stream. In the fixed-length decoding or variable-length decoding mode, the input bit stream is directly output. Then output the processed bits to the syntax element decoding module;

The syntax element decoding module receives the bits output by the bit decoding module and the entropy decoding mode and context parameters output by the control module, and performs syntax element decoding. Syntax element decoding is to decode the bits output by the bit decoding module into syntax elements according to the entropy decoding mode and context parameters output by the control module, including fixed-length decoding, signed exponential Golomb decoding, unsigned exponential Golomb decoding, first-order to third-order Decoding modes such as Exponential Golomb decoding, truncated Exponential Golomb decoding, table lookup of special syntax elements, etc. Then transmit the decoded syntax element information to the control module;

The control module accepts the syntax element information output by the syntax element decoding module, stores the syntax elements that will be used in the subsequent decoding based on context entropy into the memory, and obtains the context parameters required for decoding the next syntax element from the memory, and obtains the following according to the standard Entropy decoding mode for a syntax element. Then output the entropy decoding mode of the next syntax element and the required context parameters to the bit decoding module and the syntax element decoding module;

Syntax elements that will be used in subsequent context-based entropy decoding stored by the control module are stored in the memory.

The syntax element decoding module, which decodes the bits output by the bit decoding module into syntax elements according to the entropy decoding mode and context parameters output by the control module, including fixed-length decoding, signed exponential Golomb decoding, unsigned exponential Golomb decoding, first-order Up to the third-order exponential Golomb decoding, truncated exponential Golomb decoding, special syntax element look-up table and other decoding modes.

In this embodiment, according to the similarity relationship between various entropy decodings in video decoding, video decoding is reorganized into three steps: bit decoding, syntax element decoding, and entropy decoding control (including context parameter storage and reading), and according to the three steps The corresponding device provided by the steps, the operation in each step has similar operation granularity and data local characteristics, which is conducive to rational allocation of operation resources, simplifies the internal interface of the general entropy decoding device in the video decoder, and improves video decoding. The efficiency of medium entropy decoding, in which the average number of decoded bits per clock cycle in arithmetic entropy decoding mode reaches more than 0.66, and the number of decoded bits per clock cycle in variable length entropy decoding mode reaches more than 0.72.

Claims (6)

1. a general entropy decoding method of video decoder, is characterized in that, comprises the following steps: Step 1, input a segment of compressed video bitstream, determine the entropy decoding mode applied to the bitstream according to the video compression standard followed by the bitstream, and obtain context parameters; Step 2, if the entropy decoding mode is arithmetic decoding, perform arithmetic decoding according to the entropy decoding mode and context parameters in step 1, obtain the bits after arithmetic decoding and output them; if the entropy decoding mode is fixed-length decoding or variable-length decoding, directly output raw bits; Step 3, according to the entropy decoding mode and context parameters obtained in the first step, and the bits obtained in the second step, perform syntax element decoding, and loop through steps 2 and 3 until a syntax element is completed and output after decoding, and Record syntax element information required for subsequent entropy decoding; Step 4: Repeat the above step 1 to step 3 until the decoding of all input bit streams is completed. 2. the general entropy decoding method of video decoder according to claim 1, is characterized in that, described entropy decoding mode, refers to the mode for entropy decoding in each video standard, comprises arithmetic decoding mode, fixed-length decoding mode And variable length decoding mode, variable length decoding mode is divided into signed exponential Golomb decoding, unsigned exponential Golomb decoding, first-order to third-order exponential Golomb decoding, truncated exponential Golomb decoding, special syntax element lookup table. 3. the general entropy decoding method of video decoder according to claim 1, it is characterized in that, described context parameter refers to in context-based adaptive variable-length decoding or context-based arithmetic decoding, when decoding Syntax element information of the required decoded neighboring blocks. 4. according to the general entropy decoding method of video decoder described in claim 1 or 3, it is characterized in that, described syntactic element information refers to the corresponding code word in the bit stream, can pass fixed-length decoding, variable Information obtained by long decoding and entropy decoding methods based on context decoding. 5. A general-purpose entropy decoding device in a video decoder, comprising: a bit decoding module, a syntax element decoding module, a control module, and a memory, wherein: The bit stream is input into the bit decoding module, and the entropy decoding mode information and context parameters are received from the control module. In the arithmetic decoding mode, the bit decoding module performs bit decoding in the arithmetic decoding, and the bit decoding is to select a table according to the context parameter to look up the table. And decode a bit according to the input bit stream, and output the processed bit to the syntax element decoding module; in the fixed-length decoding or variable-length decoding mode, the bit decoding module directly outputs the input bit stream to the syntax element decoding module; The syntax element decoding module accepts the bits output by the bit decoding module and the entropy decoding mode and context parameters in the control module, performs syntax element decoding, and transmits the decoded syntax element information to the control module; The control module receives the syntax element information output by the syntax element decoding module, stores the syntax elements that will be used in the subsequent context-based entropy decoding into the memory, and obtains the syntax elements of adjacent macroblocks required for decoding the next syntax element from the memory, Calculate the context parameters according to the MPEG-x series, H.26x series or China's AVS standard, and get the entropy decoding mode of the next syntax element, and then output the entropy decoding mode of the next syntax element and the required context parameters to the bit a decoding module and a syntax element decoding module; Syntax elements that will be used in subsequent context-based entropy decoding stored by the control module are stored in the memory. 6. the general entropy decoding device of video decoder according to claim 5, it is characterized in that, described syntax element decoding module, it decodes the bit output of bit decoding module according to the entropy decoding pattern and context parameter that control module outputs as Syntax elements, decoding modes include fixed-length decoding, signed exponential Golomb decoding, unsigned exponential Golomb decoding, first-order to third-order exponential Golomb decoding, truncated exponential Golomb decoding, and table lookup for special syntax elements.

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