JP2009060343A - Residual index decoder, and decoding method of residual index - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve throughput and a processing speed of a residual index decoder, and reduce a circuit size. <P>SOLUTION: The decoder is provided with: a coeffLevel decoder 115 which decodes output data following a VLC (Variable Length Code) decoder 100, a level decoder 111, a run decoder 113, a level, and a run, and transmits it to a zigzag scanning block 120; and a counter 114 which creates a count value by counting in the same order as that in processing of the run decoder 113 following data created by the VLC decoder 100, and transmits the count value to the run decoder 113, and the coeffLevel decoder 115. The run decoder 113 decodes the run following the count value transmitted from the counter 114. The coeffLevel decoder 115 adds an index to pixel data, following the count value transmitted from the counter 114. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a residual index decoder and a residual index decoding method. The present invention relates to a residual index decoder applied to decoding a residual_block_cavlc portion in H.264 and a decoding method of the residual index.

  In recent years, H.264 has been used as a compression encoding method for moving image data. H.264 is known. H. One of the H.264 decoding processes is a decoding process of residual_block_cavlc syntax, which is a decoding process of a residual index using a CAVLC (Context-based Adaptive Variable Length Code) method.

  The conventional residual index decoder includes a level decoder, a run decoder, and a coeff Level decoder. In the conventional residual index decoder, since the decoding process by the coeff Level decoder is performed after the decoding process by the level decoder and the run decoder, a level buffer for storing the level between the level decoder and the run decoder and the coeff Level decoder, and A run buffer for accumulating run is provided.

  The parameters in the stream are stored in the order of level and run (run_before), and after all level and run are decoded, coffLevel [] is determined in the reverse order of decoding the run.

  In addition, since the run decoder and the coeff Level decoder operate according to the run counter and the coeff Level counter in the reverse order, the run decoding and the coeffLevel [coeffNum] decoding are performed in different processing orders.

  However, since the coeff Level decoder cannot perform the decoding process until the decoding process of the level decoder and the run decoder is completed, there is a problem that the throughput is deteriorated.

  In addition, since a run buffer is provided separately from the level buffer and a coeff Level counter is provided separately from the run counter, there is a problem that the circuit scale increases.

  In addition, the provision of the run buffer has a problem that the processing speed is reduced due to the run buffer access.

  On the other hand, when the decoding process of the residual_block_cavlc syntax is realized by software, separate loop algorithms are described for the run decoding and the coeffLevel decoding.

However, since two loop algorithms are included, there is a problem that the number of steps increases.
JP 2006-287862 A

  An object of the present invention is to provide a residual index decoder and a residual index decoding method for improving throughput and processing speed and reducing circuit scale.

  According to a first aspect of the present invention, a level decoder that decodes a level indicating a DCT coefficient value quantized according to data generated by a VLC decoder, and the DCT in a predetermined order according to the data generated by the VLC decoder. The output data is decoded by adding an index to the pixel according to the run decoder that decodes run indicating the continuous number of 0s before the coefficient value, the level decoded by the level decoder, and the run decoded by the run decoder. Then, a count value is generated by counting the output data in the same order as the processing of the run decoder according to the data generated by the VLC decoder and the coeff Level decoder that transmits the output data to the zigzag scan block. And a counter that transmits a run value to the run decoder and the coeff Level decoder, the run decoder decodes the run according to a count value sent from the counter, and the coeff Level decoder is sent from the counter A residual index decoder is provided that adds an index to the pixel data according to a count value.

  According to the present invention, the throughput and processing speed can be improved and the circuit scale can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. The following examples are one embodiment of the present invention and do not limit the scope of the present invention.

  First, Example 1 of the present invention will be described. The first embodiment of the present invention is an example in which the object of the present invention is achieved using hardware.

(Constitution)
FIG. 1 is a block diagram illustrating a configuration of a residual index decoder 110 according to the first embodiment of the present invention.

  The residual index decoder 110 according to the first embodiment of the present invention is connected to a VLC (Variable Length Code) decoder 100 and a zigzag scan block 120.

  The VLC decoder 100 generates VLC decoded data by performing a syntax VLC decoding process, and transmits the VLC decoded data to the residual index decoder 110.

  The residual index decoder 110 includes a level decoder 111, a level buffer 112, a run decoder 113, a counter 114, and a coeff Level decoder 115.

  The level decoder 111 decodes the level according to the parameters of the VLC decoded data transmitted from the VLC decoder 100 and transmits the decoded level to the level buffer 112. Level is data indicating a quantized DCT coefficient value.

  The level buffer 112 is a buffer for accumulating the level transmitted from the level decoder 111.

  The run decoder 113 decodes run according to run_before and zerosLeft of the VLC decode data transmitted from the VLC decoder 100 and a count value and a decode command transmitted from the counter 114 described later, and transmits the run to the coeff Level decoder 115. run_before is data indicating the number of consecutive zeros before the DCT coefficient value, zerosLeft is data indicating the number of remaining zeros to be decoded, and run is the number of consecutive zeros before the DCT coefficient value. It is the data shown.

  The counter 114 generates a count value by counting in the same order as the processing of the run decoder 113 in accordance with the TotalCoeff and zerosLeft of the VLC decode data transmitted from the VLC decoder 100 and the count instruction transmitted from the coeffLevel decoder 115. The value and the decode command are transmitted to the run decoder 113 and the coeff Level decoder 115. The counter 114 is an up counter, for example. TotalCoeff is data indicating the number of non-zero coefficients.

  The coeffLevel decoder 115 decodes coeffLevel [coeffNum] by adding an index to the pixel according to the level stored in the level buffer 112, the run transmitted from the run decoder 113, and the count value transmitted from the counter 114, and performs zigzag scanning. Transmit to block 120. coeffLevel [coeffNum] is output data.

  The zigzag scan block 120 receives the output data transmitted from the coeffLevel decoder 115 and performs zigzag scan.

(Operation)
First, the level decoder 111 decodes all levels according to the parameters of the VLC decode data transmitted from the VLC decoder 100 and transmits the decoded levels to the level buffer 112.

  Next, the counter 114 determines zerosLeft and TotalCoeff initial values of the VLC decoded data transmitted from the VLC decoder 100, performs counting according to the count command transmitted from the coeffLevel decoder 115, and counts to the run decoder 113 and the coeffLevel decoder 115. Send values and decode instructions.

  Next, the coeff Level decoder 115 receives the run transmitted from the run decoder 113, reads the level stored in the level buffer 112, and decodes coeffLevel [coeffNum]. At this time, level and run are used for decoding coeffLevel [coeffNum] in the order of decoding. That is, coeffLevel [] is determined in descending order of coeffNum as an argument. Whether run and coeffLevel [] can be decoded is determined according to the counter value transmitted from the counter 114.

  FIG. 2 is a schematic diagram illustrating waveforms output from the respective units 111 to 115 of the residual index decoder 110 according to the first embodiment of the present invention.

  As shown in FIG. 2, the residual index decoder 110 according to the first embodiment of the present invention decodes the level decoded by the level decoder 111 and the run decoded by the run decoder 113 in the order of decoding. , Run decode processing and coeffLevel [coeffNum] decode processing can be performed in parallel.

  According to the first embodiment of the present invention, since the run decoder 113 and the coffLevel decoder 115 perform the decoding process in the same order, the throughput of the residual index decoder 110 can be improved.

  Further, according to the first embodiment of the present invention, the buffer between the run decoder 113 and the coff Level decoder 115 is not necessary, so that the circuit scale can be reduced and the processing speed due to the buffer access can be prevented from being lowered.

  Further, according to the first embodiment of the present invention, the run decoder 113 and the coff Level decoder 115 perform processing according to the common counter 114, so that the circuit scale can be reduced.

  Next, a second embodiment of the present invention will be described. The first embodiment of the present invention is an example of achieving the object of the present invention using hardware, while the second embodiment of the present invention is an example of achieving the object of the present invention using software. In addition, the description about the content similar to Example 1 of this invention is abbreviate | omitted.

  FIG. 3 is a block diagram showing a configuration of the residual index decoder 210 according to the second embodiment of the present invention.

  The residual index decoder 210 according to the second embodiment of the present invention is connected to a VLC (Variable Length Code) decoder 200, a zigzag scan block 220, and a memory 230.

  The VLC decoder 200 generates VLC decode data by performing VLC decode processing according to the VLC decode program 231 stored in the memory 230, and writes the generated VLC decode data in the memory 230.

  The residual index decoder 210 implements a residual index decoding unit 211, a level decoding unit 212, and a run & coeff Level decoding unit 213 according to the residual index decoding program 232, the level decoding program 233, and the run & coeff Level decoding program 234 stored in the memory 230.

  The zigzag scan block 220 performs zigzag scan on the processing result of the residual index decoder 210 according to the zigzag scan program 235 stored in the memory 230.

  The memory 230 controls the VLC decoding program 231 which is a control program of the VLC decoder 200, the residual index decoding program 232 which is a control program of the residual index decoder 210, the level decoding program 233, the run & coeff Level decoding program 234 and the control of the zigzag scan block 220. A zigzag scan program 235 which is a program is stored. The memory 230 is also used as a working memory in processing in the VLC decoder 200, the residual index decoder 210, and the zigzag scan block 220.

  FIG. 4 is a flowchart showing a processing procedure of the residual index decoder 210 in the residual index decoding process according to the second embodiment of the present invention.

  First, the residual index decoding unit 211 performs an operation “coeff_token” for reading VLC decoded data from the memory 230 (S401).

  If TottalCoeff of the VLC decoded data is larger than 0 (S402-YES), the level decoding means 212 performs the level decoding process described later by executing the level decoding program 233 stored in the memory 230 (S403).

  Next, the residual index decoding unit 211 executes an operation “decode zerosLeft” for decoding zerosLeft (S404).

  Next, the run & coeff Level decoding means 213 executes a run & coeff Level decoding program 234 stored in the memory 230 to perform a later-described run & coeff Level decoding process (S405).

  After S405 ends, the residual index decoding process according to the second embodiment of the present invention ends.

  On the other hand, if TottalCoeff of the VLC decoded data is smaller than 0 (S402-NO), the residual index decoding unit 211 determines that there is no need to decode run and coeffLevel [], and performs S403 to S405. Without any processing, the residual index decoding process according to the second embodiment of the present invention is terminated.

  FIG. 5 is a flowchart showing the processing procedure of the level decoding means 212 in the level decoding processing according to the second embodiment of the present invention.

  First, the level decoding unit 212 substitutes 0 as an initial value for the index variable i (S501).

  When the index variable i is smaller than the TotalCoeff of the VLC decoded data (S502-YES), the level decoding unit 212 executes an operation “decode trailing_ones_sign_flag” for decoding the parameters of the VLC decoded data (S503).

  Next, the level decoding unit 212 executes an operation “decode level” for decoding the level (S504).

  Next, the level decoding means 212 increments the index variable i (S505), and returns to S502.

  When the index variable i becomes equal to the TotalCoeff of the VLC decoded data (S502-NO), the level decoding unit 212 ends the level decoding process according to the second embodiment of the present invention, and jumps to S404 in FIG. .

  FIG. 6 is a flowchart showing a processing procedure of the run & coeff Level decoding means 213 in the run & coeff Level decoding process according to the second embodiment of the present invention.

  First, the run & coeff Level decoding unit 213 executes an operation “coeffNum = TotalCoeff + zerosLeft−1” for substituting an initial value for the variable coeffNum (S601).

  Next, the run & coeff Level decoding unit 213 substitutes 0 as an initial value for the index variable i (S602).

  When the index variable i is smaller than the value obtained by subtracting 1 from TotalCoeff of the VLC decoded data (YES in S603), the run & coeff Level decoding unit 213 calculates “coeffLevel [coeffNum] = level [ i] "is executed (S604).

  Next, the run & coeff Level decoding unit 213 executes an operation “decode run” for decoding the run (S605).

  Next, the run & coeff Level decoding unit 213 executes the operation “zerosLeft-= run” (S606).

  Next, the run & coeff Level decoding unit 213 executes an operation “coeffNum = coeffNum−run−1” for calculating the number of coefficients (S607).

  Next, the run & coeff Level decoding means 213 increments the index variable i (S608), and returns to S603.

  When the index variable i becomes equal to the value obtained by subtracting 1 from TotalCoeff of the VLC decoded data (S603-NO), the run & coeff Level decoding means 213 calculates "coeffLevel [coeffNum] =" for determining the index of the output data. level [i] "is executed (S609), and the run & coeff Level decoding process according to the second embodiment of the present invention is terminated.

  FIG. 7 is a schematic diagram illustrating an example of a source code of residual index decoding processing according to the second embodiment of the present invention.

  As illustrated in FIG. 7, the residual index decoder 210 according to the second embodiment of the present invention decodes level and zerosLeft from the stream and writes them in the memory 230. Next, the initial value of coeffNum is determined according to TotalCoeff and zerosLeft, and a for loop is called. In the for loop, an index is taken with TotalCoeff, and coeffLevel [coeffNum] is determined together with the level written in the memory 230 while decoding run. After determining coeffLevel [coeffNum], the coeffNum that becomes the index of the next coeffLevel is updated by the decoded run. It also updates zerosLeft, which is necessary for decoding the next run in the same loop.

  Next, a modification of the second embodiment of the present invention will be described. A modification of the second embodiment of the present invention is an example in which the run & coeff Level decoding process is realized using a while statement.

  FIG. 8 is a flowchart showing a processing procedure of the run & coeff Level decoding means 213 in the run decoding process according to the modification of the second embodiment of the present invention.

  First, the run & coeff Level decoding unit 213 performs an operation “coeffNum = TotalCoeff + zerosLeft−1” for substituting an initial value for the variable coeffNum (S801).

  Next, the run & coeff Level decoding means 213 substitutes 0 as an initial value for the index variable i (S802).

  When the coeffNum of the VLC decoded data is 0 or more (S803-YES), the run & coeff Level decoding means 213 executes an operation “coeffLevel [coeffNum] = level [i]” for determining the index of the output data ( S804).

  Next, the run & coeff Level decoding unit 213 executes an operation “decode run” for decoding the run (S805).

  Next, the run & coeff Level decoding unit 213 executes the operation “zerosLeft-= run” (S806).

  Next, the run & coeff Level decoding means 213 performs an operation “coeffNum = coeffNum−run−1” for calculating the number of coefficients (S807).

  Next, the run & coeff Level decoding unit 213 increments the index variable i (S808), and returns to S803.

  When the coeffNum of the VLC decode data becomes a negative value (S803-NO), the run & coeff Level decode means 213 ends the run & coeff Level decode processing according to the modification of the second embodiment of the present invention.

  FIG. 9 is a schematic diagram illustrating an example of a source code of a residual index decoding process according to a modification of the second embodiment of the present invention.

  As shown in FIG. 9, the residual index decoder 210 according to the modification of the second embodiment of the present invention decodes level and zerosLeft from the stream and writes them in the memory 230. Next, the initial value of coeffNum is determined according to TotalCoeff and zerosLeft, and the while loop is called. In the while loop, the processing is continued while coeffNum indicating the number of non-zero coefficients whose index has not been determined is 0 or positive. In the while loop, coeffLevel [coeffNum] is determined together with the level written in the memory 230 while decoding the run. After determining coeffLevel [coeffNum], the coeffNum that becomes the index of the next coeffLevel is updated by the decoded run. It also updates zerosLeft, which is necessary for decoding the next run in the same loop.

  According to the second embodiment of the present invention, in addition to the same effects as those of the first embodiment of the present invention, when the decoding process of residual_block_cavlc is realized by software, the loop algorithm of decoding of run and decoding of coeffLevel is shared. Therefore, the number of processing steps can be reduced.

It is a block diagram which shows the structure of the residual index decoder 110 which concerns on Example 1 of this invention. It is the schematic which shows the waveform output from each part 111-115 of the residual index decoder 110 which concerns on Example 1 of this invention. It is a block diagram which shows the structure of the residual index decoder 210 which concerns on Example 2 of this invention. It is a flowchart which shows the process sequence of the residual index decoder 210 in the residual index decoding process which concerns on Example 2 of this invention. It is a flowchart which shows the process sequence of the level decoding means 212 in the level decoding process which concerns on Example 2 of this invention. It is a flowchart which shows the process sequence of the run & coeff Level decoding means 213 in the run & coeff Level decoding process which concerns on Example 2 of this invention. It is the schematic which shows an example of the source code of the residual index decoding process which concerns on Example 2 of this invention. It is a flowchart which shows the process sequence of the run & coeff Level decoding means 213 in the run decoding process which concerns on the modification of Example 2 of this invention. It is the schematic which shows an example of the source code of the residual index decoding process which concerns on the modification of Example 2 of this invention.

Explanation of symbols

100, 200 VLC decoder 110, 210 Residual index decoder 111 Level decoder 112 Level buffer 113 Run decoder 114 Counter 115 Coeff Level decoder 120, 220 Zigzag scan block 211 Residual index decoding means 212 Level decoding means 213 Run decoding means 230 Memory

Claims (5)

A level decoder for decoding a level indicating a DCT coefficient value quantized according to data generated by the VLC decoder;
A run decoder that decodes run indicating the number of consecutive zeros before the DCT coefficient value in a predetermined order according to data generated by the VLC decoder;
A coeff Level decoder that decodes output data by adding an index to pixel data according to the level decoded by the level decoder and the run decoded by the run decoder, and transmits the output data to a zigzag scan block;
A counter that generates a count value by counting in the same order as the processing of the run decoder in accordance with the data generated by the VLC decoder, and transmits the count value to the run decoder and the coeff Level decoder.
The run decoder decodes the run according to the count value transmitted from the counter,
The coeff Level decoder adds an index to the pixel data according to the count value transmitted from the counter.   The counter according to claim 1, wherein the counter generates the count value by taking a difference between run decoded by the run decoder and zerosLeft indicating the number of remaining zeros of data generated by the VLC decoder. Residual index decoder.   The residual index decoder according to claim 1 or 2, wherein the counter is an up counter. The coeff Level decoder sends a count command to the counter;
4. The residual index decoder according to claim 1, wherein the counter generates the count value according to a count command transmitted from the coeffLevel decoder. 5. Decoding a level indicating a DCT coefficient value quantized according to the data generated by the VLC decoder;
Decoding zeroLeft indicating the number of remaining zeros of the data generated by the VLC decoder according to the data generated by the VLC decoder;
Decoding run indicating the number of consecutive 0s before the DCT coefficient value in a predetermined order according to the data generated by the VLC decoder;
A method of decoding a residual index, comprising adding an index to a pixel according to the decoded level and run.

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