JP2000013794A - Moving picture coding apparatus, moving picture coding method, moving picture decoding apparatus, and moving picture decoding method - Google Patents

Abstract

(57) [Problem] To reduce the code amount when coding a quantized transform coefficient obtained after orthogonal transform and quantization using a variable length coding table. SOLUTION: When encoding a quantized transform coefficient 17 obtained by performing orthogonal transform and quantization in block units, VL
The C table group selection unit 4c6 sets the V table according to the condition at the time of quantization for each area obtained by dividing the block into a plurality of areas.
The variable-length coding table group is selected from the LC table storage unit 4C1, and the VLC table selection unit 4c8 performs coding of the quantized transform coefficient in the region from the selected variable-length coding table group. The variable length coding table to be used is selected, and the area data coding unit 4c10 is selected.
Encodes the quantized transform coefficient using the selected variable-length encoding table, and generates the quantized transform coefficient data 17.
Output as

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transforming and quantizing an input image signal in units of blocks to generate quantized transform coefficients, and to store the quantized transform coefficients in a variable length coding table for each predetermined area in the block. And a moving image coding method for generating a coded bit stream by performing variable length coding on the basis of the above, and decoding an image signal from the coded bit stream to restore an input image signal before coding. And a moving picture decoding method.

[0002]

2. Description of the Related Art Conventionally, as a means for efficiently encoding an image signal, for example, MPEG-4 (Moving Picture Expert), which has been standardized by ISO / IEC JTC11 / SC29 / WG111, has been developed.
s Group Phase-4) video coding reference method (Verificatio
n Model 8.0, below VM8.0, ISO / IEC JTC11 / SC29 / WG11 / N
As adopted in 1796), a method of performing discrete-length cosine transform (DCT), quantization, and variable-length coding of the obtained quantized transform coefficients after quantization has been used. MPEG-4
In order to perform variable-length coding of the quantized transform coefficients in a block, the block is scanned in a predetermined order, a flag (LAST) indicating whether a non-zero coefficient is the last in the block, (LAST, RUN, LEVEL) using the same variable length coding table in the block
Is variable-length-encoded. The variable length coding table used at this time is (LAST, RUN, LEVE)
L), a code word having a predetermined code length is assigned based on the occurrence probability of (LAST, RUN, LEVEL). That is, a codeword having a long code length is assigned to a low occurrence probability (LAST, RUN, LEVEL), whereas a short code length code is assigned to a high occurrence probability (LAST, RUN, LEVEL). Try to assign words.

[0003]

However, in the above-mentioned conventional method, the quantized transform coefficients in a block are encoded by one variable-length encoding table. In order to reduce the variation in the value of the transform coefficient, when the transform coefficient prediction that encodes the difference data with the transform coefficient of the preceding and succeeding blocks is performed, the level of the transform coefficient is compared with the case where the transform coefficient prediction is not performed. When the probability of occurrence of (RUN, LEVEL) is different, for example, when the encoding is performed using the same variable-length encoding table, the redundancy at the time of encoding the transform coefficient increases. there were.

Also, since the frequency of occurrence of the transform coefficient level varies depending on the quantization step size at the time of quantization, encoding using the same variable length encoding table also requires encoding of the transform coefficient. There is a problem that the redundancy at the time of the conversion is increased.

Accordingly, the present invention has been made to solve the above-described problem, and it is intended to determine whether or not transform coefficient prediction has been performed, or conditions for various encodings such as a quantization step size. It is an object of the present invention to provide a moving picture coding apparatus and a moving picture coding method capable of improving coding efficiency when switching is performed adaptively.

In particular, in the present invention, a block, which is a coding unit of an input image signal, is divided into several regions, and a variable length coding table used when performing variable length coding of transform coefficients in each region is adapted. It is an object of the present invention to provide a moving picture coding apparatus and a moving picture coding method capable of improving coding efficiency by switching between them.

It is another object of the present invention to provide a moving picture decoding apparatus and a moving picture decoding method capable of correctly decoding an encoded bit stream generated by the moving picture coding apparatus and the moving picture coding method. .

[0008]

In order to achieve the above object, according to the present invention, an input image signal is transformed and quantized in block units to generate a quantized transform coefficient, and the quantized transform coefficient is stored in the block. In a moving image encoding apparatus that performs variable length encoding by a variable length encoding table for each predetermined area to generate an encoded bit stream, a plurality of variable length encoding table groups that are grouped in advance, and the plurality of variable length A variable-length coding table group selecting means for selecting one variable-length coding table group from a group of coding tables; and a variable-length coding table using the variable-length coding table of the selected group. A coded bitstream for performing long coding to generate a coded bitstream including information indicating a variable length coding table of the selected group; A generation unit, is characterized in that it comprises a.

In the following invention, the plurality of variable length coding table groups are grouped in advance based on coding conditions at the time of quantization, and the variable length coding table group selecting means includes: It is characterized in that a variable length coding table group is selected based on coding conditions at the time of quantization.

In the next invention, the variable length coding table group is obtained from a plurality of variable length coding tables grouped based on the presence or absence of a transform coefficient prediction for calculating a difference between quantized transform coefficients between blocks. The variable length coding table group selecting means selects a corresponding variable length coding table group from the plurality of variable length coding table groups based on the presence or absence of the transform coefficient prediction, and generates a coded bit stream. The means is characterized in that it generates an encoded bit stream including information indicating the presence or absence of the transform coefficient prediction as information indicating the variable length coding table of the selected group.

Further, in the following invention, the variable length coding table group comprises a plurality of variable length coding tables grouped according to a quantization step size, and the variable length coding table group selecting means includes: A corresponding variable-length coding table group is selected from the plurality of variable-length coding table groups based on the quantization step size, and the coding bitstream generating unit generates a variable-length coding table of the selected group. An encoded bit stream including information on the quantization step size is generated as information to be indicated.

Further, in the following invention, the variable-length coding table group selected by the variable-length coding table group selecting means further includes a variable-length coding table based on the position of the quantized transform coefficient in the area. It is characterized by having variable length coding table switching means for switching the coding table.

Further, in the following invention, when the quantized transform coefficients are subjected to variable-length coding, a case where all the quantized transform coefficients in each area are zero is regarded as an invalid area, and a coefficient other than zero in the area. A region data validity / invalidity judging means for judging a case where there is a valid area, and a coded bit stream generating means, when the area data validity / invalidity judging means judges that the area is an effective area, the selected variable While encoding the quantized transform coefficient in the area by the long encoding table and generating an encoded bit stream including information indicating the variable length encoding table used at that time, when it is determined that the area is invalid, Generates an encoded bit stream including information indicating that the area is invalid.

In the next invention, the coded bit stream generating means, when performing variable length coding on the quantized transform coefficient, if the corresponding code word is not in the variable length coding table, the corresponding code While converting the quantized transform coefficients without words into a value included in the variable length coding table by a predetermined method, the quantized transform coefficients after the conversion are subjected to variable length coding by the variable length table, An encoded bit stream including information indicating a conversion method is generated.

In the next invention, a coded bit stream is input, and coded data subjected to variable length coding for each block included in the coded bit stream is subjected to variable length decoding to obtain a quantized transform coefficient. In the video decoding device for decoding the image signal by inversely quantizing and inversely transforming the quantized transform coefficient, a plurality of variable length decoding tables grouped into groups and encoding from the encoded bit stream are performed. Variable-length decoding table group that decodes information indicating the variable-length coding table group used on the side and selects a variable-length decoding table group from the variable-length decoding table group based on the variable-length coding table group information Using the selection unit and the variable length decoding table of the selected group to decode the encoded data in a variable length to restore the quantized transform coefficients That it is characterized in that it comprises a quantized transform coefficient restoring unit.

Further, in the following invention, the plurality of variable length decoding table groups are grouped in advance based on encoding conditions at the time of quantization. As the information indicating the variable length coding table group used on the encoding side from the bit stream, the information indicating the coding condition at the time of quantization is decoded, and the variable length decoding is performed based on the coding condition at the time of quantization. It is characterized in that a table group is selected.

Further, in the following invention, the variable length decoding table group includes a plurality of variable length decoding tables grouped based on the presence or absence of a transform coefficient prediction for calculating a difference between quantized transform coefficients between blocks. The variable-length decoding table group selecting means decodes information indicating presence / absence of quantization transform coefficient prediction from the coded bit stream as information indicating the variable-length coding table group used on the encoding side, It is characterized in that a variable length decoding table group is selected based on information indicating whether or not there is a transform coefficient prediction.

Further, in the following invention, the variable length decoding table group comprises a plurality of variable length decoding tables grouped based on a quantization step size, and the variable length decoding table group selecting means includes As information indicating the variable length coding table group used on the encoding side from the bit stream, decoding the quantization step size, based on the decoded quantization step size, selecting a variable length decoding table group, Is what you do.

Further, in the following invention, further, the quantization transform coefficient restoring means switches the plurality of variable length decoding tables in the variable length decoding table group selected by the variable length decoding table group selecting means to perform the quantization. And a variable length decoding table selecting means for switching the variable length decoding table based on the position of the quantized transform coefficient in the area when decoding the quantized transform coefficient.

Further, in the following invention, when the quantized transform coefficients in the area are all zero, the quantized transform coefficient restoring means indicates that the area is invalid, and the quantized transform coefficient is not zero. If there is more than one, decode the variable length coding table selection information indicating the variable length decoding table used to decode each quantized transform coefficient in the area, Determining means for determining whether or not the area is invalid, and a quantizing transform for setting all quantized transform coefficients in the area to zero when the determining means determines that the area is invalid. Coefficient zero setting means.

Further, in the following invention, a judging means for judging whether or not information indicating that the quantized transform coefficient has been converted by the predetermined method on the encoding side from the encoded bit stream has been decoded, When it is determined by the determining means that the information has been decoded, the decoding is performed using the variable-length decoding table when the quantized transform coefficient is restored, and then the reverse of the conversion of the predetermined method is performed. Means for performing processing to restore the quantized transform coefficients before the transform.

In the next invention, a quantized transform coefficient is created by transforming and quantizing an input image signal in units of blocks, and the quantized transform coefficient is converted into a variable length code defined for each predetermined area in the block. In the moving picture coding method of generating a coded bit stream by performing variable length coding using a coding table, a variable length coding table group is selected from a plurality of grouped variable length coding tables, and the selection is performed. Variable-length coding the quantized transform coefficients using a variable-length coding table of the selected group, and generating a coded bit stream including information indicating the selected variable-length coding table. It is.

Further, in the next invention, when selecting a variable length coding table group from a plurality of grouped variable length coding tables, the variable length coding table group is selected based on a coding condition at the time of quantization. In addition, an encoded bit stream including information on encoding conditions at the time of the quantization is generated as information indicating the selected variable-length encoding table.

In the next invention, a coded bit stream is input, and coded data subjected to variable length coding for each block included in the coded bit stream is subjected to variable length decoding to obtain a quantized transform coefficient. In the moving picture decoding method for decoding the image signal by inversely quantizing and inversely transforming the quantized transform coefficient, when the quantized transform coefficient is restored, it is used on the encoding side from the encoded bit stream. Decoding the information indicating the variable-length coding table group, and selecting a variable-length decoding table group from the plurality of grouped variable-length decoding tables based on the variable-length coding table group information. The coded data is variable-length decoded using the variable-length decoding tables of the groups, and the quantized transform coefficients are restored.

Also, in the next invention, when the quantized transform coefficient is restored, information indicating the variable length coding table group used on the encoding side is used as the information indicating the encoding condition at the time of quantization from the encoded bit stream. Is decoded, and a variable length decoding table group is selected based on the information on the encoding conditions at the time of quantization.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 In the first embodiment, a moving picture coding apparatus using the coding apparatus according to claim 1 will be described. FIG. 1 is a block diagram showing a configuration of the video encoding device according to the first embodiment. In the figure, 1 is input shape data, 2 is a shape encoding unit, 3
Is a shape coded data, 4 is a variable length coding unit, 5 is a multiplexing unit, 6 is locally decoded shape data, 7 is input texture data, 8 is an intra / inter determination unit, 9 is a mode instruction flag, and 10 is motion. A detection unit, 11 is a motion vector, 12 is a motion compensation unit, 13 is a predicted image signal, 14 is a prediction error signal, 15 is a coded image signal, 16 is a texture coding unit, 17 is quantized transform coefficient data, 18 Is a texture local decoding unit, 19 is a local decoding prediction error signal, 20 is a locally decoded image signal, 21 is a switching unit, 22 is a reference image signal, 23
Is a memory, 24 is a shape data codeword, 25 is an additional information codeword, 26 is a block data codeword, 27 is a motion vector codeword, 28 is a coded bit stream, 29 is a subtractor, 30 is an adder, and 31 is an adder. Transform coefficient prediction determination information, which is one of the conditions for texture encoding, and 32 is a quantization step size, which is another condition for texture encoding.

FIG. 2 is a diagram showing the internal configuration of the variable length coding unit 4 of the first embodiment shown in FIG. In the figure,
4a is a shape data variable length coding unit, 4b is an additional information variable length coding unit, 4c is a transform coefficient variable length coding unit, and 4d is a motion vector variable length coding unit.

Next, the operation of the entire apparatus will be described with reference to FIGS. This apparatus is an apparatus that divides an input digital image sequence into image objects in MPEG-4, that is, partial areas having the same characteristics such as motion and picture, and encodes the image objects in units. However, if one frame is defined as one image object, encoding can be performed in image frame units. The image object is composed of texture data representing a color density level in a circumscribed rectangle surrounding the image object, and shape data representing an effective pixel in the circumscribed rectangle. The texture data is composed of a pair of a luminance signal component and a color difference signal component, and corresponds to an input image signal. The shape data is binary matrix data in which the inside of the object is 1 and the outside of the object is 0.

The operation is as follows. First, the input shape data 1 is passed to the shape encoding unit 2 where it is encoded and locally decoded, and output as the shape encoded data 3 and the locally decoded shape data 6, respectively. You. The shape-encoded data 3 is subjected to variable-length encoding by a variable-length encoding unit 4,
Are multiplexed into the coded bit stream 28. The local decoding shape data 6 includes a texture encoding unit 16, a texture local decoding unit 18, a motion compensation unit, and the like, which are used for encoding texture data, performing motion compensation, and the like for only effective pixels. 12, motion detector 10
Sent to

On the other hand, the input texture data 7 is cut out for each block called a macroblock, and the following operation is performed for each macroblock. That is, first, the intra / inter determination unit 8 determines whether to encode the texture data 7 in the image object or between the image objects. Here, when it is determined to perform intra (in an image object) encoding, the intra / inter determining unit 8 passes the input texture data 7 as it is to the texture encoding unit 16 as the encoded image signal 15.

On the other hand, when the coding is determined to be inter (between image objects), the intra / inter determining unit 8 sends the input texture data 7 to the motion detecting unit 10 for performing the motion compensation prediction. The motion detection unit 10 searches for a region most similar to the luminance signal component of the input texture data 7 within a predetermined range of the reference image signal 22 stored in the memory 23, The change in the position up to the position of the similar region is output to the motion compensator 12 and the variable-length encoder 4 as a motion vector 11.

The motion vector 11 output to the variable length coding unit 4 is reduced in redundancy by the motion vector variable length coding unit 4 d of the variable length coding unit 4, and then encoded by the multiplexing unit 5. Multiplexed to stream 28.

In the motion compensating section 12, the motion detecting section 1
0 based on the motion vector 11 obtained from
3 to the predicted image signal 13 from the reference image signal 22 stored in
Is extracted. Then, the subtracter 29 passes the prediction error signal 14, which is the difference between the predicted image signal 13 and the input texture data 7, to the texture encoding unit 16 as the encoded image signal 15.

The intra / inter mode selected by the intra / inter determining section 8 is output to the switching section 21 and is subjected to variable length encoding by the variable length encoding section 4 as a mode instruction flag 9. Then, it is passed to the multiplexing unit 5 and multiplexed into the coded bit stream 28.

The texture encoding section 16 orthogonally transforms and quantizes the coded image signal 15 and outputs it as quantized transform coefficient data 17. The quantized transform coefficient data 17 is subjected to variable-length coding with reduced redundancy by the transform coefficient variable-length coding unit 4c of the variable-length coding unit 4, and then to the coded bit stream 28 by the multiplexing unit 5. Are multiplexed.

The quantized transform coefficient data 17 output from the texture encoding unit 16 is also transmitted to the texture local decoding unit 18 where the texture local decoding unit 18 performs inverse quantization and inverse orthogonal transform to perform local decoding. It becomes the prediction error signal 19. This local decoding prediction error signal 19 is obtained when the mode instruction flag 9 indicates the inter mode.
From the switching unit 21 to the predicted image signal 13 from the motion compensation unit 12
Are output, and are added to the predicted image signal 13 by the adder 30 and output as the locally decoded image signal 20.

On the other hand, when the mode instruction flag 9 indicates the intra mode, the switching unit 21 selects the 0 signal. The addition with the image signal 13 is not performed, and is output as the local decoded image signal 20 as it is. In addition,
The locally decoded image signal 20 output from the adder 30 is written to the memory 23 because it is used as a reference image signal 22 for motion compensation prediction for the next and subsequent frames.

Next, the configurations and operations of the texture encoding unit 16 and the transform coefficient variable length encoding unit 4c, which are the most important elements of the first embodiment, will be described.

FIG. 3 is an internal configuration diagram of the texture encoding unit 16 of the first embodiment shown in FIG. In the figure,
16a is a block data extracting unit, 16b is block data, 16c is a DCT unit, 16d is a DCT coefficient, 16e is a quantizing unit, 16f is a quantized transform coefficient, and 16g is a transform coefficient predicting unit.

Next, the operation in the texture encoding section 16 will be described. In the texture encoding unit 16, first, from the encoded image signal 15, a block serving as a unit for performing a discrete cosine transform (hereinafter, DCT), which is one of orthogonal transforms, for example, a block of usually 8 pixels × 8 pixels is used. , And is extracted by the block data extraction unit 16a.

The extracted block data 16b is a DC
The signal is input to the T unit 16c and DCT is performed. DCT unit 1
The DCT coefficient 16d output from the quantization unit 16c
At e, the quantization is performed based on the quantization step size, and the quantized transform coefficient is output to the transform coefficient prediction unit 16g as the quantized transform coefficient 16f.

The transform coefficient predicting section 16g performs transform coefficient prediction. In the transform coefficient prediction, a predicted value of a quantized transform coefficient of a coding target block is obtained from a quantized transform coefficient of a surrounding block, and a difference value between the quantized transform coefficient and the predicted value is calculated. This difference value is encoded by the transform coefficient variable length encoding unit 4c (see FIG. 2).

Here, when the quantized transform coefficient of the block to be encoded has a correlation with the quantized transform coefficient of the surrounding block, the difference between the quantized transform coefficient of the surrounding block and the quantized transform coefficient of the surrounding block is obtained. The difference quantization transform coefficient has a smaller value variation than the original quantization transform coefficient. For example, assume that the values of the quantized transform coefficients are distributed in the range of 0 to 255 with the same appearance frequency. The entropy for such a quantized transform coefficient is 8 bits, and the code length of the code word corresponding to each level value is 8 bits for any level.

When the quantized transform coefficient of the block to be coded has a strong correlation with the quantized transform coefficient of a neighboring block, and especially when the quantized transform coefficient of The frequency of appearance of the difference quantization transform coefficient, which is the difference value between the block and the quantization transform coefficient, increases near zero. Since the entropy of such a signal having a biased appearance frequency is smaller than the entropy of the original quantized transform coefficient, if the code length is assigned according to the appearance frequency, the average code of the differential quantized transform coefficient is obtained. The length can be smaller than 8 bits. in this way,
By performing the transform coefficient prediction and encoding the differential quantized transform coefficient, the amount of code generated when encoded by the transform coefficient variable length encoding unit can be reduced.

Next, an example of the operation of the transform coefficient prediction unit 16g will be described. FIG. 4 is an explanatory diagram of transform coefficient prediction by the transform coefficient predictor 16g. The operations described below are based on ISO / IE
C JTC1 / SC29 / WG11 This corresponds to intra AC / DC prediction disclosed in MPEG-4 Video VM8.0. Transform coefficient prediction is particularly effective in intra-mode D where the dispersion of values is large.
This is performed on the C coefficient and the quantized transform coefficient (hereinafter, abbreviated as a transform coefficient) of the low-frequency component located in the hatched portion in FIG.

Assuming that the block to be coded is X as shown in FIG. 4, the transform coefficients of the blocks around block X, for example, block B or block C, are used as the predicted values of the transform coefficients. A difference between the calculated transform coefficient prediction value and the quantized transform coefficient is obtained, and a difference quantized transform coefficient is output. However, when there is no correlation with the surrounding blocks and the difference quantized transform coefficient is larger than the original quantized transform coefficient, the original quantized transform coefficient is output without performing the transform coefficient prediction.

The transform coefficient predictor 16g outputs the difference quantized transform coefficient or the quantized transform coefficient obtained as described above as the quantized transform coefficient data 17. The quantized transform coefficient data 17 is subjected to variable length coding in the transform coefficient variable length coding unit 4c. The conversion coefficient prediction unit 16g outputs information indicating whether or not the conversion coefficient prediction has been performed as the conversion coefficient prediction determination information 31.

Next, the detailed configuration and operation of the transform coefficient variable length coding unit 4c will be described. FIG. 5 is a diagram showing the internal configuration of the transform coefficient variable length coding unit 4c shown in FIG. 2, and FIG. 6 is a flowchart showing the operation thereof. In FIG. 5, 4c1 is a VLC table storage unit, 4c2 is a switching unit,
4c3 is a DC coefficient data encoding section, 4c4 is AC coefficient data, 4c5 is a DC coefficient codeword, 4c6 is a VLC table group selection section, 4c7 is a VLC table group information, 4c8 is a VLC table selection section, and 4c9 is a VLC table selection information. , 4c10 is an area data encoding unit, 4c
11 is an AC coefficient codeword.

The transform coefficient variable length coding unit 4c according to the first embodiment configured as described above divides a block into a plurality of regions, and divides each block into statistical characteristics of the transform coefficients in the region. Based on this, a plurality of variable length coding tables are set. When coding the transform coefficients in the area, the variable length coding table to be used is adaptively switched from among the set plurality of variable length coding tables. When setting a plurality of variable-length coding tables for each region, the variable-length coding table is set based on whether or not transform coefficient prediction has been performed on the position of the region and the transform coefficient in the region.

Hereinafter, the operation will be described in detail with reference to FIGS. (1) DC coefficient data encoding First, the mode instruction flag 9 is determined by the switching unit 4c2.
(Step S1) If the intra mode is indicated, the quantized transform coefficient data 17 is converted to the DC coefficient data encoding unit 4c3.
To encode the DC coefficient data (step S
2) Output the DC coefficient codeword 4c5. On the other hand, in the case of the inter mode, since there is no DC coefficient,
Switching to the coefficient data encoding unit 4c3 is not performed.

(2) Encoding of AC coefficient data Next, the encoding of the AC coefficient data 4c4 of the quantized transform coefficient data 17 will be described. The encoding of the AC coefficient data 4c4 is performed by dividing the block into a plurality of regions,
This is performed for each area. When DCT is performed for each block, the occurrence probability of the value of the transform coefficient differs depending on the position in the block. Therefore, the inside of the block is divided into a plurality of regions based on the statistical characteristics of the image data.

For example, as shown in FIG. 7, the AC coefficient area in the block is divided into four areas 1-4. Area 1
Is a region including a low-frequency component in a vertical direction parallel to the scanning direction, and a region 2 is a region including a low-frequency component in a horizontal direction perpendicular to the scanning direction. For this reason, a high value AC coefficient is likely to occur in the region 1 and the region 2. On the other hand, the region 3 or the region 4 is a region containing a high-frequency component,
An AC coefficient of zero or a small value is likely to occur.

The encoding of the AC coefficient data in the areas 1 to 4 is performed by scanning the AC coefficient data in each of the areas 1 to 4 in a predetermined order from the low frequency component to the high frequency component, and obtaining a plurality of (RUN) data. , LEVEL) data with variable length coding (hereinafter, VLC
(Variable Length Coding)).

Therefore, the areas 1 to 4 are scanned in the order determined for each of the areas 1 to 4, and (RUN, LEVEL) data is obtained (step S3). Here, RUN is the number of consecutive zeros when scanning, and LEVEL is the absolute value of the following non-zero coefficient.

For example, when the area 2 is scanned in the direction of arrow A shown in FIG. 7, the first coefficient scanned is -8, and the first (RUN, LEVEL) is (0,-). 8)
become. Next, after one 0 continues, -1 follows.
The next (RUN, LEVEL) data is (1, -1). The above processing is repeated until a non-zero coefficient in the region reaches the end.

The (RUN, LEVEL) data obtained by scanning is subjected to variable length coding by a VLC table set based on the occurrence probability of (RUN, LEVEL) data in each area. The VLC table indicates that a symbol having a high occurrence probability has a short code length according to the occurrence probability of the symbol.
Assign a long code length to symbols with a low probability of occurrence,
It is a table in which symbols and their corresponding codewords are paired. The symbol of the VLC table used when encoding the AC coefficient data corresponds to (RUN, LEVEL) data. (R
Since the probability of occurrence of (UN, LEVEL) differs for each region, by setting a different VLC table for each region, the code amount of AC coefficient data can be reduced.

The value of the AC coefficient differs depending on various coding conditions when DCT and quantization are performed. For example, when transform coefficient prediction that takes the difference from the AC coefficient of the surrounding macroblock is performed, the value of the AC coefficient is smaller than when the transform coefficient prediction is not performed.
Further, it differs depending on the size of the quantization step size at the time of quantization. Therefore, considering these conditions, VL
By setting the C table, the code amount of the AC coefficient data can be further reduced.

In view of the above, in the first embodiment, the VLC table group is selected for each of the areas 1 to 4 according to the statistical characteristics of the (RUN, LEVEL) data in the areas 1 to 4 and selected. (RU) in the specified VLC table group
(N, LEVEL) data is switched.

A method of selecting a VLC table for each of the areas 1 to 4 will be described below. (2.1) VLC table group selection Since the appearance probability of (RUN, LEVEL) differs depending on the region 1 to 4 or the scanned position in the region 1 to 4,
A plurality of different VLC tables are set for each of the areas 1 to 4. Also, the appearance probability differs depending on the encoding conditions when the quantized transform coefficient data is obtained. For this reason, in the first embodiment, the conditions for texture encoding are based on transform coefficient prediction determination information 31 (see FIG. 3) obtained from transform coefficient predictor 16g of texture encoder 16.
Select a VLC table group.

First, a VLC table group, which is a combination of VLC tables that can be selected to encode each area in a block, is assigned to a VLC table group selection unit 4c6.
Is selected (Step S4). For example, in the case of division as shown in FIG.
Select an LC table group. At this time, when scanning from the low frequency component to the high frequency component, the selection is made based on the characteristic that the lower the frequency component, the higher the appearance probability of the data of the larger LEVEL, and the higher the frequency component, the more the LEVEL or zero increases. Here, a method of selecting a VLC table group based on the transform coefficient prediction determination information 31 for each of the regions 1 to 4 will be described with reference to FIG.

FIG. 8 shows a VLC table group in which a pair of (RUN, LEVEL) stored in the VLC table storage unit 4C1 and a code word to which a code length according to the occurrence probability is assigned. Since the appearance probability of (RUN, LEVEL) differs depending on whether or not the transform coefficient is predicted, or the position where the transform coefficient is scanned in the areas 1 to 4,
As shown in FIG. 8, whether or not the transform coefficient prediction has been performed, and the VLC corresponding to each case for each of the regions 1 to 4
A VLC table group having a plurality of tables is prepared.

For example, as shown in FIG. 8, if the transform coefficient prediction is not performed for region 1 and region 2, V
The LC table group selection unit 4c6 calculates the conversion coefficient prediction determination information 31 and the appearance probability of (RUN, LEVEL) based on
VLC table 1A containing low LEVEL symbols, VLC containing high LEVEL symbols and short RUN symbols
A table group T1 having tables 2A, 3A, etc. is selected and a VLC indicating the selected table group T1
The table group information 4c7 is stored in the VLC table selecting section 4.
Output to c8.

On the other hand, when the prediction of the conversion coefficient is performed, the effect of reducing the variation of the coefficient level is obtained, so that the VLC including the higher LEVEL is compared with the case where the prediction of the conversion coefficient is not performed. The need for a table is small. Therefore, the VLC table group selection unit 4c6
Based on the conversion coefficient prediction determination information 31 and the appearance probability of (RUN, LEVEL) when the conversion coefficient prediction is performed, a small LE
VLC table 1B containing VEL symbol and intermediate LEV
The EL selects a table group T2 having a VLC table 2B or the like including a short RUN symbol, and outputs VLC table group information 4c7 indicating the selected table group T2 to the VLC table selection unit 4c8.

For regions 3 and 4, a high LE
Since the appearance probability of the VEL symbol is small, a table group T3 having VLC tables 4, 5 and the like including long RUN symbols is selected instead, and VLC table group information 4c7 indicating the selected table group T3.
To the VLC table selection unit 4c8.

It should be noted that the VLC table group, on the decoding side corresponding to the first embodiment, converts the transform coefficient prediction determination information for each of the regions 1 to 4 in the block, similarly to the encoding side of the first embodiment. Since the VLC table group information 4c7 is selected as the additional information, it is not necessary to multiplex the VLC table group information 4c7 into the bit stream 28. That is, as shown in FIG. 1 and FIG. 2, the transform coefficient prediction determination information 31 includes an additional information codeword 25 in the bit stream 28 transmitted to the decoding side in order to determine whether to perform the transform coefficient prediction.
Since it is multiplexed as one of them, it is sufficient to use this. Therefore, since it is not necessary to multiplex the VLC table group information 4c7 on the bit stream 28 to the decoding side, it is possible to select a VLC table group used for each area without newly increasing the code amount. .

(2.2) Region Data Coding Next, variable length coding of the AC coefficient data 4c4 in each of the regions 1 to 4 will be described. The AC coefficient data 4c4 is represented by a combination of a plurality of (RUN, LEVEL) data obtained by scanning each of the areas 1 to 4 in a predetermined order. Certain AC coefficient data 4c4
Are output to the VLC table selection unit 4c8 and the area data encoding unit 4c10.

In the VLC table selecting section 4c8, VLC
Input (RUN, LEVEL) based on VLC table group information 4c7 from table group selection section 4c6.
A VLC table used for variable-length encoding of the AC coefficient data 4c4, which is data, is adaptively selected from the VLC table groups selected by the VLC table group selection unit 4c6 (step S5). Selected VL
VLC table selection information 4c9 indicating the C table is output to the area data encoding unit 4c10. In addition, VLC
The criterion for table selection is determined, for example, by the level of LEVEL of the AC coefficient data 4c4, which is (RUN, LEVEL) data.

Next, the operation of the area data encoding unit 4c10 will be described. The region data encoding unit 4c10 selects a VLC table stored in the VLC table storage unit 4c1 based on the VLC table selection information 4c9 output from the VLC table selection unit 4c8, and changes (RUN, LEVEL) data. Long encoding is performed (step S6).

In the variable length coding, for example, first, a code word corresponding to (RUN, LEVEL) is searched from the selected VLC table. If a corresponding codeword is found, it is output as an AC coefficient codeword 4c11. If a corresponding codeword is not found, a fixed-length codeword called an escape code is output. When an escape code is output, RUN and LEVEL are each fixed-length encoded, and RUN and LEVEL are added after the escape code.
A sequence of each fixed-length codeword is output as an AC coefficient codeword 4c11.

In this way, all (RUN,
LEVEL) The processing of steps S5 to S6 is repeated until the encoding of the data is completed (“No” in step S7).

Further, all (RUN, LEVE) in a certain area
L) When the data is variable-length coded (step S7)
"Yes"), (R
It is determined whether the (UN, LEVEL) data is variable-length coded (step S8), and the (R) of all the other areas 1 to 4 in the block is determined.
If it is determined that the (UN, LEVEL) data has not been subjected to the variable length coding ("No" in step S8), the processing from step S3 to step S7 is repeated (step S8).

On the other hand, when it is determined that all the (RUN, LEVEL) data in each of the areas 1 to 4 in the block have been subjected to variable length coding (“Yes” in step S8), the transform coefficient variable length coding unit 4c completes the variable length coding process and returns to D
The C coefficient codeword 4c5 and the AC coefficient codeword 4c11 are passed to the multiplexing unit 5 as the block data codeword 26, and the multiplexing unit 5 multiplexes the coded bitstream 28.

Here, in the first embodiment, the selection of the VLC table from the selected VLC table group is performed using the LEVEL value of each (RUN, LEVEL) data. If the decoding side, LEVEL
Need to select a VLC table before decoding.
For this reason, the VLC table selection information 4c9 is sent to the additional information variable length coding unit 4b to be coded to be a VLC table selection codeword and multiplexed as one of the additional information codewords 25 into the bit stream 28. .

Here, as a method of encoding the VLC table selection information 4c9, the current (RUN, LEVEL) data,
VL used to encode the next (RUN, LEVEL) data
There is a method of performing variable-length encoding using the C table selection information 4c9 (NEXT) as a set. The variable-length coding table used at this time is a table in which a set of (NEXT, RUN, LEVEL) stores a code word whose code length is determined according to the appearance probability.

In this method, the first (RUN, LEVE)
VLC table selection information 4c used to encode L)
9 needs to be separately encoded as VLC table initial switching information. The VLC table selection information 4c9 used at the time of encoding the second and subsequent (RUN, LEVEL) is encoded as a set with the immediately preceding (RUN, LEVEL) data. When the non-zero LEVEL is the last in the area, NEX
T is information indicating that the (RUN, LEVEL) paired therewith is the last (RUN, LEVEL) in the area.

As described above, when switching a plurality of VLC tables and encoding each area, as described above,
It is necessary to encode the VLC table selection information 4c9 as additional information. For example, as shown in FIG. 8, the VL used when the transform coefficient prediction is performed and the VL used when the
When the C table group is switched, the number of VLC tables to be switched when the conversion coefficient prediction is performed is two of the tables 1B and 2B of the table group T2. Therefore, the VLC table selection information 4c9 is encoded with a fixed length. In this case, the required code length is 1 bit.

However, if the VLC table group is not switched between when the conversion coefficient prediction is performed and when it is not performed, it is necessary to switch from the five types of VLC tables, and the VLC table selection information 4c9 is fixed length. The code length required when encoding is 3 bits. As described above, even when the VLC table selection information 4c9 is combined with (RUN, LEVEL) and subjected to variable length encoding, if the number of NEXTs increases, the number of combinations of NEXT, RUN, and LEVEL increases. The code amount of the code word corresponding to (NEXT, RUN, LEVEL) also increases. As described in the first embodiment, for each region, a VLC table group is selected according to the statistical characteristics of (RUN, LEVEL) data in the region, and each VLC table group is selected from among the selected VLC table groups. (RUN, LEVEL)
By switching the VLC table used when encoding data, the amount of code necessary to encode the VLC table selection information 4c9 can be reduced.

As described above, in the first embodiment, the block is divided into a plurality of regions, and the VLC table group is divided into regions according to the position of each region in the block and the transform coefficient prediction determination information. Is selected, and a VLC table is selected from the selected VLC table group, and the transform coefficient is subjected to variable-length encoding. Therefore, the transform coefficient can be encoded with a smaller code amount. Become.

In the first embodiment, a VLC table group to be switched in each area is prepared in advance based on the position of each area and the transform coefficient prediction determination information 31, so that the type of VLC table to be switched can be changed. The amount of code required for encoding can be reduced.

Embodiment 2 The second embodiment is characterized in that the configuration of the transform coefficient variable length coding unit 4c is changed. Therefore, the configuration and operation of the transform coefficient variable length coding unit 4c according to the second embodiment will be mainly described.

FIG. 9 is an internal configuration diagram of the transform coefficient variable length coding unit 4c according to the second embodiment. In the figure, reference numeral 32 denotes a quantization step size at the time of quantization output from the quantization unit 16e of the texture encoding unit 16 shown in FIG.

That is, in the transform coefficient variable length coding unit 4c according to the second embodiment, instead of the transform coefficient prediction determination information 31 input to the VLC table group selection unit 4c6 as a condition for texture coding, quantization The feature is that a step size 32 is input.
Other operations are the same as those of the transform coefficient variable length coding unit 4c according to the first embodiment.

Next, the operation of VLC table group selecting section 4c6 according to the second embodiment will be described.

The VLC table group selection unit 4c6 determines the position in the block of the area recognized in advance by the VLC table group selection unit 4c6, and the quantization step size 32 input from the outside as a condition for texture encoding. , Select a selectable VLC table group to encode each region in the block.

For example, a large quantization step size 32
In the area quantized by, the small LEVEL or zero increases, and the appearance probability of the data of the high LEVEL decreases. As described above, according to the quantization step size 32, (RUN, LE
Since the appearance probabilities of the (VEL) data are different, the VLC table group selection unit 4c6 selects the VLC table group according to the quantization step size 32.

Note that the quantization step size 32 is
As shown in FIG. 2 and FIG. 2, the information at the time of performing the inverse quantization on the decoding side includes the additional information variable length coding unit 4 of the variable length coding unit 4.
b, and after being multiplexed into the bit stream 28 by the multiplexing unit 5 as one of the additional information codes 25, the decoding side uses this to perform variable-length decoding The table group can be selected in the same way as the encoding side.

Therefore, in the second embodiment, there is no need to multiplex new additional information by selecting a VLC table group into the bit stream 28 as in the first embodiment. However, as in the case of the first embodiment, the selection of the VLC table from the selected VLC table group is determined according to each (RUN, LEVEL) data.
When the decoding is performed using the value of LEVEL, the decoding side needs to select a VLC table before decoding the LEVEL. Therefore, the VLC table selection information 4c9 is sent to the additional information variable length coding unit 4b to perform coding. Then, the VLC table is selected as a VLC table selection codeword and multiplexed into the bit stream 28 as one of the additional information codewords 25.

Therefore, according to the second embodiment, the block is divided into a plurality of regions, and the VLC is determined for each region according to the position of the region in the block and the quantization step size.
Select a table group and select the selected VL
Since the VLC table is selected from the C table group and the AC coefficient data in each area is subjected to variable length coding, the transform coefficient can be coded with a smaller code amount and the compression efficiency is improved. The effect is obtained.

In the second embodiment, the quantization step size 32 is used when selecting the VLC table group, but the transform coefficient prediction determination information 31 described in the first embodiment is used.
And the quantization step size 32, VL
The C table group may be selected.

Embodiment 3 In the third embodiment, VL
From the VLC table group selected by the C table group selection unit, the selection of the VLC table used to encode each (RUN, LEVEL) data in the region is changed from a low frequency component to a high frequency component in the region. It is characterized in that it is performed based on the statistical characteristics of the LEVEL value such that the appearance probability of a LEVEL having a value of zero or a smaller value becomes higher as it goes.

For example, a large value level is likely to occur in a low frequency component. Therefore, when (RUN, LEVEL) data to be encoded is data scanned with a low frequency component, a large value LEVEL is included. Select a VLC table.

On the other hand, in the case of data scanned with a high-frequency component, the VLC includes a small value level and long RUN data, and assigns a short code length to them.
Select a table. Hereinafter, a description will be given of the transform coefficient variable length coding unit 4c including the VLC table selection unit that selects the VLC table based on the scanned position in the area.

FIG. 10 shows the internal configuration of the transform coefficient variable length coding unit 4c according to the third embodiment.

Switching section 4c2, DC coefficient data encoding section 4
c3, the operation of the VLC table group selection unit 4c6 is the same as that of the first or second embodiment, except for the operation of the VLC table selection unit 4c8.

That is, the VLC table group selection unit 4
As in the first and second embodiments, c6 can be selected for each region in a block based on encoding conditions at the time of texture encoding such as the quantization step size 32 or the transform coefficient prediction determination information 31. Select the VLC table group,
As VLC table group selection information 4c7, VLC
Output to the table selection unit 4c8.

In the VLC table selecting section 4c8, VLC
From the VLC table group selected by the table group selection unit 4c6, AC (RUN, LEVEL) data
The VLC table used to encode the coefficient data 4c4 is selected.

Here, the appearance probability of (RUN, LEVEL) differs depending on the scanned position in the area. Even in the same region, the level of zero or a small value increases as going from the low frequency component to the high frequency component. That is, the appearance probability of the LEVEL value differs depending on the position where the LEVEL is scanned.

Therefore, unlike the first and second embodiments, the VLC table selecting unit 4c8 of the third embodiment does not input the (RUN, LEVEL) data as the AC coefficient data 4c4, The selection of the VLC table is performed according to the position of the scan in the table. That is,
Each of the regions 1 to 4 is further divided into a plurality of regions, and the VLC table is selected according to which region the (RUN, LEVEL) data to be encoded has been scanned.

The (RUN, LEVEL) data is stored in each area 1 to
4, the encoding is performed in the order scanned in a predetermined order, so that the decoding side (RUN, LEVEL)
Can be matched with the scan position on the encoding side based on the already decoded (RUN, LEVEL). For this reason, the decoding side can select a variable length decoding table to be used at the time of decoding based on the scan position. Therefore, the encoding side of the third embodiment uses the VLC table selection information 4c9 as additional information in a bit stream. There is no need for multiplexing.

As a result, in the first and second embodiments, the VLC table selection information 4
Although it was necessary to multiplex c9, the third embodiment does not require the VLC table selection information 4c9 to be multiplexed into the bit stream 28. The code amount of the stream 28 can be reduced.

After the VLC table selection information 4c9 is output from the VLC table selection section 4c8 to the area data encoding section 4c10, the area data encoding section 4c10 sets the VLC table as in the first and second embodiments. VLC table selection information 4c9 output from selection section 4c8
The VLC table is switched and selected based on the VLC table, and (RUN, LEVEL) data, which is the AC coefficient data 4c4, is subjected to variable-length encoding. The operation of the area data encoding unit 4c10 is the same as in the first and second embodiments, and
Repeat until (RUN, LEVEL) data is encoded.

Therefore, in the third embodiment, the VLC table is selected according to the scan position in the area.
c9 need not be multiplexed into the bitstream,
The effect is obtained that the code amount of the additional information necessary for switching the VLC table can be reduced.

Embodiment 4 The fourth embodiment is characterized in that the configuration of the transform coefficient variable length coding unit 4c is changed.

FIG. 11 shows an internal configuration diagram of transform coefficient variable length coding section 4c according to the fourth embodiment. In the figure, reference numeral 4c12 denotes an area data valid / invalid judgment unit, and 4c13.
Is an area valid / invalid information code, 4c14 is an area valid / invalid information coding unit, and 4c15 is an area valid / invalid information codeword.

Next, the operation will be described.
The difference in the operation is that the area data valid / invalid judgment unit 4c1
2 and the area valid / invalid information coding unit 4c14, and other configurations and operations are the same as those in the first or second embodiment.
Is exactly the same as Therefore, the operation of the area data valid / invalid determination unit 4c12 and the corresponding operation of the area valid / invalid information coding unit 4c14 will be described below.

First, in the transform coefficient variable length coding unit 4c according to the fourth embodiment, the area data valid / invalid determining unit 4c12
Determines whether or not the AC coefficients in the area are all zero for each area, and determines the determination result as area valid / invalid information 4c1.
Output as 3. Area valid / invalid information encoding unit 4c1
4 encodes the area valid / invalid information 4c13,
Output as area valid / invalid information codeword 4c15. As a method of encoding the area valid / invalid information 4c13, for example, variable-length coding may be performed on the area valid / invalid information for all the areas in the block.

When the AC coefficient data 4c4 in the area is all zero, the area is regarded as an invalid area.
The encoding of the next area is skipped without encoding the AC coefficient data 4c4 in the area. Therefore, the AC in the region
When the coefficient data 4c4 is all zero, only the area valid / invalid information 4c13 needs to be encoded, and the code amount of the AC coefficient data 4c4 can be reduced.

In the case of the transform coefficient variable length coding unit 4c described in the first and second embodiments, the VLC table selection information 4c9 indicating the VLC table used for coding each (RUN, LEVEL) data is represented by: The encoding is performed by the additional information variable length encoding unit 4b.

Therefore, in the fourth embodiment, the area valid / invalid information 4c13 is stored in the first (RU) in each of the areas 1 to 4.
(N, LEVEL) data may be encoded in the first VLC table selection information 4c9 indicating the VLC table used for encoding. For example, the additional information variable length coding unit 4b determines that the first VLC table selection information 4c9 is
When the coding of the area is not performed because the AC coefficients in the area are all zero, it is set to “0”, and the information indicating the VLC table when the n types of VLC tables are switched and coded is “1” to “1”. If “n” is set, the area valid / invalid information 4c13 can be substituted by the VLC table selection information 4c9. This eliminates the need for the area valid / invalid information encoding unit 4c14 itself.

Next, the variable length coding unit 4c described in the fourth embodiment shown in FIG. 4 is more advantageous than the conventional one obtained when applying to the coding of macroblock data in MPEG-4. The effect, that is, the effect that the bit stream structure that is different depending on the encoding mode in the related art can be made common and the circuit for syntax analysis in the decoding device can be simplified will be described.

FIG. 12 shows the structure of a coded bit stream when macroblock data in the conventional MPEG-4 is coded. Conventionally, in MPEG-4, for each VOP,
When performing intra / inter coding (I-VOP / P-VOP),
It has a different bit stream structure when bidirectional prediction coding (B-VOP) is performed. Intra coding refers to VO
In this mode, encoding is performed using only the information in P. The inter coding is a mode in which motion compensation prediction is performed using the immediately preceding VOP. In addition, bidirectional prediction encoding is a mode in which motion compensation prediction is performed using VOPs before and after one and the like.

FIG. 12A shows the structure of a bit stream B1 in the case of a conventional I-VOP / P-VOP. In the figure, shape attribute information D1 is shape attribute information such as a motion vector of shape data. The valid macroblock information D2 is information indicating the validity / invalidity of the macroblock. If the transform coefficient data of the macroblock is all zero and the motion vector is zero, the macroblock becomes an invalid macroblock and the following information Are not multiplexed into the bitstream.
Effective color difference block information / macro block type D3 is
The effective chrominance block information is a set of the effective chrominance block information and the macroblock type, and the effective chrominance block information indicates the validity / invalidity of the chrominance block in the macroblock. If the conversion coefficient data in the chrominance block is all zero, the chrominance block becomes invalid. The AC prediction instruction information D4 is information indicating whether or not transform coefficient prediction has been performed on the AC coefficient in the macroblock, and is the same as the transform coefficient prediction determination information 31. The effective luminance block information D5 indicates whether the luminance block in the macro block is valid or invalid. If the conversion coefficient data in the luminance block is all zero, the luminance block is invalid. Differential quantization step size D6
Represents a difference from the quantization step size of the immediately preceding macroblock data when the quantization step size differs from the immediately preceding macroblock data. The interlace information D7 is information necessary for an interlaced image. The motion data D8 is data relating to motion existing when motion compensation is performed. The shape data D9 is information necessary for encoding a VOP having an arbitrary shape. The block data D10 exists only when the effective color difference block information or the effective luminance block information D5 indicates that the block is an effective block.

FIG. 12B shows the structure of a bit stream B2 in the case of a conventional B-VOP. Only the multiplexing method of the macroblock type D10 and the effective block information D12 is different. Specifically, the I-VOP / P-VO shown in FIG.
In the case of P, the chrominance block and the luminance block are separately multiplexed for the effective block information, and the effective information of the chrominance block is paired with the macro block type to form the effective chrominance block information / macro block type D3. As variable length coding. The luminance block information is a combination of valid / invalid information of four luminance blocks and is variable-length coded as effective luminance block information D5.

On the other hand, in the case of the B-VOP shown in FIG. 12B, the macroblock type D11 and the effective chrominance block information are separately multiplexed, and the validity / invalidity of each of the luminance block and the chrominance block is determined. The information shown is fixed-length coded as effective block information D12.

Thus, the conventional I-VOP / P-VOP and B-VOP
, The multiplexing method of the effective block information indicating whether or not the quantized transform coefficients (AC coefficients) in the block are all zero in the area is different, and the structure of the bit stream is different.

However, according to the variable length coding unit 4c described in the fourth embodiment, for each region in the block, the region data validity / invalidity determination unit 4c12 determines whether the quantized transform coefficient AC
It is determined whether the coefficient is zero or not, and the area valid / invalid information encoding unit 4c14 encodes the area valid / invalid information 4c13 and multiplexes it into the bit stream 28 as the area valid / invalid information encoding unit 4c14. It is determined for each block whether the quantized transform coefficient AC coefficient in the block is zero,
The bit stream 28 is used as effective block information.
Need not be multiplexed.

FIG. 13 shows a bit stream B3 obtained when the variable length coding unit 4c of the fourth embodiment is applied to coding of macroblock data in MPEG-4. The effective block information is stored in the bit stream D3
Therefore, the common structure of the bit stream B3 shown in FIG. 13 is obtained in any of the I-VOP, P-VOP, and B-VOP encoding modes. In the case of the fourth embodiment, the AC coefficient data D
13, the area valid / invalid information D14 is set.

As described above, when the variable length coding means described in the fourth embodiment is applied to the coding of macroblock data in MPEG-4, the coding modes for intra, inter, and bidirectional prediction are set. Regardless, the structure of the common bit stream D3 is as shown in FIG.

Therefore, according to the moving picture coding apparatus of the fourth embodiment, the means for analyzing the syntax, which is the structure of the bit stream, can be shared on the decoding side regardless of the coding mode. In this case, an effect is obtained that a circuit configuration for syntax analysis is simplified.

Embodiment 5 FIG. The fifth embodiment is characterized by the configuration of the area data encoding unit 4c10 of the transform coefficient variable length encoding unit 4c.

FIG. 14 is a detailed internal configuration diagram of the area data encoding unit 4c10 of the transform coefficient variable length encoding unit 4c in the present embodiment. In the figure, 4c101 is V
LC table search unit, 4c102 is an escape code,
4c103 is a conversion coefficient conversion unit, 4c104 is conversion AC coefficient data, 4c105 is a conversion flag, and 4c106 is a conversion coefficient fixed length decoding unit.

Next, the operation will be described. The VLC table search unit 4c101 converts the input conversion coefficient data AC
The code word corresponding to the coefficient data (RUN, LEVEL) 4c4 is V
Search in the VLC table of the LC table storage unit 4c1. If a codeword corresponding to the AC coefficient data (RUN, LEVEL) 4c4 is found in the VLC table, the codeword is output as an AC coefficient codeword 4c11 as in the first to fourth embodiments.

Here, the feature of the fifth embodiment is as follows.
The operation when no data is found in the VLC table will be described in detail. First, the VLC table search unit 4c10
When the codeword corresponding to the input AC coefficient data 4c4 is not in the VLC table, 1 outputs a fixed-length codeword called an escape code 4c102 and the AC coefficient data 4c4 to the conversion coefficient conversion unit 4c103.

The conversion coefficient conversion unit 4c103 converts the RUN or LEVEL value of the AC coefficient data 4c4. The first conversion is performed on LEVEL among RUN or LEVEL values of the AC coefficient data 4c4. The converted LEVEL * is VL
It is obtained by subtracting the maximum value (LMAX) of the LEVEL of the AC coefficient data included in the C table. In particular,
It is shown in the following equation 1.

LEVEL * = sign (LEVEL) × [abs (LEVEL−LMAX)] (Expression 1) where sign (LEVEL) is 1 if LEVEL is 0 or more, and −1 otherwise. Abs (LEVEL) is an absolute value of LEVEL.

Then, the VLC table search unit 4c101
Searches the VLC table again using the converted AC coefficient data 4c104 (RUN, LEVEL *). Here, conversion A
When a code word corresponding to the C coefficient data 4c104 (RUN, LEVEL *) is found in the VLC table, a code indicating that the value of LEVEL has been converted after the escape code, and a code detected from the VLC table. With a word
Output as AC coefficient codeword 4c11.

On the other hand, the conversion A in which the first conversion is performed
When the codeword corresponding to the C coefficient data 4c104 (RUN, LEVEL *) is not found in the VLC table, the conversion coefficient conversion unit 4c103 performs the second conversion. The second conversion is performed on RUN. The converted RUN * is the maximum value (RMA) of the RUN of the AC coefficient data contained in the VLC table.
X) +1 is obtained. Specifically, it is shown in the following equation 2.

RUN * = RUN− (RMAX + 1) (Equation 2)

Then, the VLC table search unit 4c101
Is the new conversion AC coefficient data 4c105 (RUN *, LEVEL
Search the VLC table again using *). Here, this new converted AC coefficient data 4c105 (RUN *, LEVEL *)
Is found in the VLC table, the code indicating that the value of RUN has been converted and the codeword detected from the VLC table are added after the escape code, and the AC coefficient codeword is added. Output as 4c11.

On the other hand, the conversion A in which the second conversion is performed
If the codeword corresponding to the C coefficient data 4c105 (RUN *, LEVEL *) is not found in the VLC table, RU
N and LEVEL are each fixed-length coded, and after the escape code, a code indicating that the AC coefficient data has been fixed-length coded and a fixed-length codeword of the AC coefficient data are added, and A
Output as C coefficient codeword 4c11.

As described in the first embodiment, (RU
N, LEVEL) and VLC table selection information 4c9 (NEXT) used to encode the next (RUN, LEVEL)
Similar processing can be performed when performing variable length coding.

Therefore, according to the fifth embodiment, when performing variable length coding of AC coefficient data, if there is no data corresponding to the AC coefficient data to be coded in the VLC table, the AC coefficient data is converted. Then, the VLC table is searched again based on the converted AC coefficient data, and the variable-length coding is performed, so that the effect of further improving the compression efficiency can be obtained.

Embodiment 6 FIG. In the sixth embodiment, a moving image decoding device that decodes an encoded bit stream generated by the moving image encoding device described in the first or second embodiment will be described.

FIG. 15 is a block diagram showing a configuration of a moving picture decoding apparatus according to the sixth embodiment. In the figure, 101 is an encoded bit stream, 102 is a syntax analysis unit, 103 is a shape data codeword, 104 is a block data codeword, 105 is an additional information codeword, 106
Is a motion vector codeword, 107 is a variable length decoding unit, 108
Is shape encoded data, 109 is quantized transform coefficient data,
110 is additional information, 111 is a motion vector, 112 is a shape decoding unit, 113 is a texture decoding unit, 114 is a motion compensation unit, 115 is decoded shape data, 116 is a decoded prediction error signal, 117 is a memory, 118 is a reference image, Reference numeral 119 denotes position information in the decoded macroblock screen, reference numeral 120 denotes a predicted image, reference numeral 121 denotes a decoding and adding unit, reference numeral 122 denotes a decoded image, and reference numeral 123 denotes a switching unit. Note that reference numeral 110a is a mode instruction flag included in the additional information 110.

FIG. 16 is a diagram showing the internal configuration of the variable length decoding unit 107 in FIG. In the figure, 107a is a shape data variable length decoding unit, 107b is a transform coefficient variable length decoding unit, 107c is an additional information variable length decoding unit, and 107d is a motion vector variable length decoding unit. Note that reference numeral 110 b denotes an encoding condition used in texture encoding, which is the transform coefficient prediction determination information 31 on the encoding side or the quantization step size 32 included in the additional information 110.

Next, the operation of the entire apparatus will be described with reference to FIGS. First, the coded bit stream 101 is subjected to a shape data codeword 103, a block data codeword 104,
It is separated into an additional information codeword 105 and a motion vector codeword 106,
After being subjected to variable-length decoding by the transform coefficient variable-length decoding unit 107b, the additional information variable-length decoding unit 107c, and the motion vector variable-length decoding unit 107d, the shape encoded data 108 is sent to the shape decoding unit 112, and the quantized transform coefficient data is sent to the shape decoding unit 112. 109 and various kinds of additional information 110 are sent to the texture decoding unit 113, and the motion vector 111 is sent to the motion compensation unit 114. It should be noted that the motion compensation unit 114 inputs the decoded macroblock in-screen position information 119 from the variable length decoding unit 107.

The shape decoding unit 112 outputs the shape encoded data 1
08 is decoded and output as decoded shape data 115.
In the texture decoding unit 113 and the motion compensation unit 114, the decoded shape data 115
It is used for decoding texture data and performing motion compensation.

The texture decoding unit 113 inversely transforms the quantized transform coefficient data 109 using the quantization step size included in the additional information 110, and then performs inverse orthogonal transform to obtain a decoded prediction error signal 116. Decoding prediction error signal 116
Is sent to the decoding addition section 121.

The motion compensator 114 converts the position information 119 of the macroblock to be decoded in the picture and the encoded bit stream 1
The predicted image 120 is extracted from the reference image 118 in the memory 117 in accordance with the decoded motion vector 111 from 01 and output to the switching unit 123.

The switching section 123 outputs the decoded additional information 11
When the intra-encoding is indicated based on the mode instruction flag 110a indicating the encoding mode on the encoding side included in 0, the predicted image 120 is not required for generating the decoded image, and thus the output is switched to the 0 output side. On the other hand, in the case of the inter encoding, since the predicted image 120 is necessary for generating the decoded image, the output side of the predicted image 120 is switched.

The decoding addition section 121 outputs the decoded prediction error signal 116 output from the texture decoding section 113 as it is to the decoded image 122 based on the mode instruction flag 110 a included in the additional information 110 in the case of an intra-coded block. On the other hand, in the case of an inter-coded block, the prediction image 120 is added to the decoded prediction error signal 116 output from the texture decoding unit 113, and the resultant is output as a decoded image 122. Note that the decoded image 122 is
The data is written to the memory 117 for use as the reference image 118 in the subsequent VOP decoding processing.

Next, the operations of the transform coefficient variable length decoding unit 107b and the texture decoding unit 113, which are the most important elements of the sixth embodiment, will be described.

FIG. 17 is an internal block diagram of the transform coefficient variable length decoding unit 107b of FIG. In FIG. 17, 107
b1 is a switching unit, 107b2 is a DC coefficient data decoding unit, 1
07b3 is the decoded DC coefficient, 107b4 is the AC coefficient data codeword, and 107b5 is VLD (Variable Length deco).
ding; variable length decoding) Table storage unit, 107b6 is V
LD table group selection unit, 107b7 VLD table group information, 107b8 area data decoding unit, 1
07b9 is VLC table selection information, 107b10 is V
LD table selection unit, 107b11 is a VLD table,
107b12 is a decoded AC coefficient. The VLD table storage unit 107b5 stores a VLD table group and a VLD table having the same contents, for example, corresponding to the VLC table group and the VLC table of the VLC table storage unit 4C1 (see FIG. 5 and the like) on the encoding side. Have been.

FIG. 18 shows a transform coefficient variable length decoding section 107b.
6 is a flowchart showing the operation of the first embodiment. Switching unit 107b1
Is the mode instruction flag 110 included in the additional information 110
Based on a, it is determined whether the coding mode of the coding block to be decoded is intra coding or inter coding (step S101). If the coding mode is an intra coding block (step S101 “ Intra ”),
Block data codeword 104 is converted to DC coefficient data decoding unit 1
07b2, and decodes the DC coefficient data included in the block data codeword 104 (step S102).
It is output as the decoded DC coefficient 107b3, and then the AC coefficient data is decoded.

On the other hand, in the case of the inter mode (“inter” in step S101), since the decoding processing of the DC coefficient data in step S102 is not performed, only the decoding of the AC coefficient data is performed. Since the AC coefficient data is encoded for each of a plurality of divided regions in the block, decoding is performed for each region.

That is, first, the AC in each area is
Variable-length decoding (hereinafter referred to as V
A table group (abbreviated as LD (Variable Length Decoding)) is selected (step S103). The selection of the VLD table group is performed by the VLD table group selection unit 10.
7b6, the position of the region in the block and the coding condition for texture coding of the transform coefficient prediction determination information 31 or the quantization step size 32 used in the transform coefficient variable length coding unit 4c on the coding side. This is performed based on 110b.

Since the transform coefficient prediction determination information 31 or the quantization step size 32 is necessary at the time of texture decoding, the bit stream 10
Since they are multiplexed into 1, they can be decoded and used. The operation of VLD table group selection section 107b6 is the same as the operation of VLC table group selection section 4c6 described in the first or second embodiment.

On the encoding side, AC coefficient data is encoded by performing variable length encoding on (RUN, LEVEL) data obtained by scanning the area in a predetermined order. At this time, the variable length coding table used for coding each (RUN, LEVEL) data is selected from the VLC table groups selected by the VLC table group selection unit 4c6. In the transform coefficient variable length coding unit 4c described in the first or second embodiment, each (RUN,
LEVEL) The type of the VLC table used to encode the data is encoded as VLC table selection information 4c9.

Therefore, in transform coefficient variable length decoding section 107b described in the sixth embodiment, area data decoding section 1
07b8 is included in each block data codeword 104.
The VLC table selection information 107b9 used for encoding the (RUN, LEVEL) data is decoded, and the VLC table selection information 107b9 is decoded by the VLD table selection unit 107b1.
Output to 0.

In the VLD table selection unit 107b10,
Based on the VLC table group information 107b9, (RUN, LEVEL) is read from the VLD table storage 107b5.
VLD table 107b1 used to decrypt data
Select 1 and output to area data decoding section 107b8
(Step S104).

In the area data decoding section 107b8, the VLD
VLD table 10 from table selector 107b10
Using (7b11), the (RUN, LEVEL) data in the area is decoded.

Specifically, first, the AC coefficient data codeword 107b4 included in the block data codeword 104 is
A search is made in the VLD table 107b11 and the corresponding
If (RUN, LEVEL) data is found, it is output as decoded AC coefficient data 107b12.

On the other hand, if the corresponding (RUN, LEVEL) data is not found and an escape code is detected, the AC coefficient data codeword 107b4, which is the next fixed-length codeword of RUN and LEVEL, is used. Fixed-length decoding and (R
UN, LEVEL) data can be obtained, and this is output as decoded AC coefficient data 107b12. The above processing of steps S104 to S105 is performed for all (RUs) in the area.
Repeat until N, LEVEL) data is decoded (step S1).
06 “No”).

Then, all (RUN, LEVE) in a certain area
L) When the decoding of the data is completed (step S106)
"Yes"), it is determined whether or not the processing of steps S103 to S106 has been performed for all the areas in the block (step S107). If not (step S107 "No"), the process proceeds to step S107. While the processing of S103 to S106 is performed, if performed ("Yes" in S107), the above processing is terminated.

Then, as described in the first embodiment, (R
UN, LEVEL) data and VLC table selection information 107b9 used to encode the next (RUN, LEVEL) data
In the case of decoding (NEXT, RUN, LEVEL) data in which (NEXT) is combined, the (LC, RUN) data and the VLC table selection information 107 used to decode the next (RUN, LEVEL) data are also used.
The basic operation is the same except that variable length decoding is performed together with b9 (NEXT).

The above decoding process is performed on all the regions in the block, and the obtained decoded DC coefficient 107b3
Then, based on (RUN, LEVEL) of the decoded AC coefficient data 107b12, a process reverse to the scan on the encoding side is performed to obtain quantized transform coefficient data 109. Note that the quantized transform coefficient data 109 is output to the texture decoding unit 113.

Next, the detailed configuration and operation of the texture decoding unit 113 will be described. FIG. 19 shows the structure of the texture decoding unit 11.
3 is an internal configuration diagram of FIG. In the figure, 113a is a switching unit, 110b1 is transform coefficient prediction determination information, 113c is a transform coefficient predictor, 113d is a differential quantization transform coefficient, 113d
e is an adjacent block quantized transform coefficient, 113f is a quantized transform coefficient, 113g is an inverse quantization unit, 113h is a quantization step, 113i is a DCT coefficient, 113j is an inverse DCT unit,
It is. 110b1 is transform coefficient prediction determination information which is one of the encoding conditions 110b for texture encoding included in the additional information 110.

Next, the operation will be described. First, the switching unit 113
As for a, when the transform coefficient prediction determination information 110b1 included in the decoded additional information 110 indicates that transform coefficient prediction is to be performed, the transform coefficient prediction unit 113c performs transform coefficient prediction.

The transform coefficient predicting unit 113c receives the difference quantized transform coefficient 113d, adds the quantized transform coefficient 113e of the neighboring block, and obtains the quantized transform coefficient 113f.
Here, the prediction of the quantized DC coefficient is performed by adding the quantized DC coefficient of a nearby block as a predicted value to the differential quantized DC coefficient. Selection of a block used for prediction is performed in the same manner as on the encoding side.

The prediction of the quantized AC coefficient is performed by first determining the transform coefficient prediction determination information 110b included in the additional information 110.
1 to determine whether or not a transform coefficient prediction has been performed,
When transform coefficient prediction is performed on the quantized AC coefficient, the quantized AC coefficient of the neighboring block is added to the differential quantized AC coefficient as a predicted value, as in the encoding side.

Thus, the transform coefficient predicting section 113c
Calculates the quantized DC coefficient and the quantized AC coefficient, and outputs the obtained quantized DC coefficient and the quantized AC coefficient to the inverse quantization unit 113g as the quantized transform coefficient 113f.

In the inverse quantization unit 113g, the additional information 110
Are inversely quantized using the quantization step size 113h included in the DCT coefficient 113i.
The inverse DCT section 113j performs inverse DCT on the DCT coefficient 113i and outputs the result as a decoded prediction error signal 116.

Therefore, according to the sixth embodiment, on the encoding side, a block is divided into a plurality of regions, and a VLC table group used for encoding AC coefficient data for each region is defined as a transform coefficient of each block. The VLC table is selected based on the prediction determination information or the quantization step size.
Even when coefficient data ((RUN, LEVEL) data) is encoded and a bit stream is transmitted, decoding can be performed correctly.

Embodiment 7 FIG. The seventh embodiment shows another embodiment of the transform coefficient variable length decoding unit described in the sixth embodiment. The variable length coding unit 4c described in the third embodiment performs variable length coding. The transform coefficient variable length decoding unit that decodes the encoded transform coefficients will be described.

FIG. 20 is an internal configuration diagram of the transform coefficient variable length decoding unit 107b according to the seventh embodiment. In the figure, reference numeral 107b13 denotes position information, and the area data decoding unit 107b8 of the seventh embodiment outputs VLC table selection information 107b9 (see FIG. 17) to the VLD table selection unit 107b10 as in the sixth embodiment. , But the position information 107b13 is output.

Next, the operation will be described. The switching unit 107
The operations of b1, the DC coefficient data decoding unit 107b2, and the VLD table group selection unit 107b6 are the same as those in the sixth embodiment, and the VLD table group selection unit 107b6
May be performed in the same manner as in the VLC table group selection unit 4c6 on the encoding side described in the third embodiment.

Next, the VLD table selector 107b10
Selects a VLD table used to decode (RUN, LEVEL) data according to the position of the scan in the area.
Position information 107b13 indicating the position of the scan in the area
Is obtained from the area data decoding unit 107b8. The area data decoding unit 107b8 decodes the (RUN, LEVEL) data in the order of scanning on the encoding side.
Based on the (RUN, LEVEL) data, the next (RUN, LE
VEL) The position of the data can be specified, and the position information 10
7b13.

In the area data decoding section 107b8, the VLD
The (RUN, LEVEL) data is decoded using the VLD table 107b11 selected by the table selection unit 107b8. Based on the decoded (RUN, LEVEL) data, the scan position of the next (RUN, LEVEL) data to be decoded is specified, and the position information 107b13 is used as the VLD table selecting unit 10.
7b10.

Therefore, in the seventh embodiment, a block is divided into a plurality of regions, a VLC table group used for encoding AC coefficient data is selected for each region, and a VLC table group is selected from the selected VLC table groups. Since the VLD table used to decode the AC coefficient data is selected based on the scan position of the (RUN, LEVEL) data which is the AC coefficient data to be encoded, the encoding side of the third embodiment is selected. As described above, even when a bit stream in which the AC coefficient data encoded by selecting the VLC table in accordance with the scan position in each area is transmitted, decoding can be performed correctly.

Embodiment 8 FIG. The eighth embodiment is another embodiment of the transform coefficient variable length decoding unit described in the sixth embodiment or the seventh embodiment, and is performed by the transform coefficient variable length coding unit 4c described in the fourth embodiment. A description is given of a transform coefficient variable length decoding unit that decodes transform coefficients that have been subjected to variable length coding.

FIG. 21 shows an internal configuration diagram of transform coefficient variable length decoding section 107b in the present embodiment. In the figure, reference numeral 107b13 denotes an area valid / invalid information codeword;
b14 is an area valid / invalid information decoding unit, 107b15 is area valid / invalid information, 107b16 is an area valid / invalid determination unit, and 107b17 is an area data zero setting unit.

In FIG. 21, the operations differ from each other in area valid / invalid information decoding section 107b14, area valid / invalid determination section 107b16, and area data zero setting section 107b17. And so on, so that the area valid / invalid information decoding unit 10 will be described below.
7b14, the operation of the area valid / invalid determination section 107b16, and the operation of the in-area AC coefficient zero setting section 107b17 will be mainly described.

In the eighth embodiment, first, area valid / invalid information decoding section 107b14 sets block data code word 1
04 area valid / invalid information codeword 107b13
Is input and decoded, and area valid / invalid information 107b1 indicating whether or not the AC coefficient data in each area is coded.
Output as 5. Area valid / invalid determination section 107b16
Then, based on the area valid / invalid information 107b15 decoded by the area valid / invalid information decoding unit 107b14, it is determined whether or not the AC coefficient data in the area is encoded.

Here, the area valid / invalid information 107b15
Indicates that the AC coefficient data in the area has been encoded, the area valid / invalid determination unit 107b16
It outputs AC coefficient data codeword 107b4 included in block data codeword 104 to area data decoding section 107b8. In the area data decoding unit 107b8, the seventh embodiment
And the like, the VLC table selection information 107b9
(RUN, LEVEL) data in the area is decoded using the VLD table 107b11 selected by the VLD table selection unit 107b10 based on
Output as 07b12.

On the other hand, the area valid / invalid information 107b
15 indicates that the area is skipped, that is, that the AC coefficient data in the area is not encoded, the area valid / invalid determination unit 107b16 sets the area data zero setting unit 10
7b17, and the area data zero setting unit 107b1
7 sets all the AC coefficients in the area to zero, and
Output as C coefficient data 107b12.

Therefore, in the eighth embodiment, in order to reduce the code amount on the encoding side, the AC coefficient data in a certain area is not encoded, and the area valid / invalid information 10 indicating the same is not encoded.
7b15 is multiplexed into the coded bit stream, the area valid / invalid information 107b15 in the received coded bit stream is decoded, and
It is determined whether or not the AC coefficient data is zero for each area in the block, and when all the AC coefficients in the area indicate zero, encoding of the AC coefficient data in the area is not performed. As in the case of the encoding side of the fourth embodiment, even when an encoded bit stream in which the area valid / invalid information 107b15 is multiplexed is transmitted, decoding can be performed correctly.

Embodiment 9 FIG. The ninth embodiment shows another embodiment of the area data decoding unit of the transform coefficient variable length decoding unit described in the sixth to eighth embodiments, and the transform coefficient variable length described in the fifth embodiment. The transform coefficient variable length decoding unit that decodes the transform coefficient that has been subjected to the variable length coding by the coding unit 4c will be described.

FIG. 22 is an internal configuration diagram of the area data decoding unit 107b8 according to the ninth embodiment. In the figure, 107b81 is a VLD table search unit, 107b8
2 is an escape code, 107b83 is a conversion flag determination unit, 107b84 is a decoded conversion AC coefficient, 107b85 is a conversion coefficient inverse conversion unit, 107b86 is a conversion coefficient fixed length decoding unit, and 107b87 is a conversion AC coefficient codeword.

Next, the operation will be described. In the area data decoding unit 107b8, the VLD table selecting unit 107b10
(See FIG. 21.) VLD table 1 selected by
Using (07b11), the (RUN, LEVEL) data in the area is decoded.

At this time, in the area data decoding section 107b8, first, the VLD table search section 107b81 converts the (RUN, LEVEL) data corresponding to the AC coefficient data codeword 107b4 included in the block data codeword 104 into the VLD table selection section. VLD table 107 from 107b10
b11, and when the corresponding (RUN, LEVEL) data is found, this is decoded AC coefficient data 107b1.
Output as 2.

On the other hand, AC coefficient data codeword 107
When (RUN, LEVEL) corresponding to b4 is not found and the escape code 107b82 is detected, the VLD table search unit 107b81 of the area data decoding unit 107b8 sets
The escape code 107b82 and the subsequent AC coefficient data codeword 107b4 are
7b83, and the conversion flag determination unit 107b83 determines the conversion flag following the escape code 107b82.

If the conversion flag indicates that LEVEL or RUN has been converted, the conversion flag determination unit 107
b83 is a conversion AC coefficient codeword 1 following the conversion flag
07b87 is returned to the VLD table search unit 107b81.

The VLD table search section 107b81 converts the converted AC coefficient codeword 107b87 into the VLD table 107b.
b11, performs variable length decoding and decode conversion AC coefficient 107b
As 84, it is output to the transform coefficient inverse transform unit 107b85. In transform coefficient inverse transform section 107b85, decoding transform AC
The coefficient 107b84 is subjected to a process reverse to the process of the transform coefficient conversion unit 4c103 (see FIG. 14) of the encoding apparatus described in the fourth embodiment, and the decoded AC coefficient data 107 is processed.
b12 is obtained.

If the conversion flag indicates that RUN and LEVEL are each fixed-length coded, conversion flag determination section 107b83 outputs AC coefficient data codeword 107b.
4 is output to the transform coefficient fixed length decoding section 107b86. The conversion coefficient fixed-length decoding unit 107b86 performs fixed-length decoding on the RUN and LEVEL fixed-length codewords following the conversion flag to obtain decoded AC coefficient data 107b12. Similarly, the above process is repeated until all (RUN, LEVEL) data in the area is decoded.

The above decoding process is performed on all the areas in the block, and the obtained decoded DC coefficient 10
7b3 and the decoded AC coefficient data 107b12, and output by arranging them in the reverse order of the scan order on the encoding side, so that the decoded quantized transform coefficient data 109
Becomes The decoded quantized transform coefficient data 109 is output to the texture decoding unit 113 (see FIG. 15).

As described in the sixth embodiment, (RU
(N, LEVEL) data and VLC table selection information 107b9 (N
The basic operation is the same when decoding (NEXT, RUN, LEVEL) data that is a set of (EXT).

Therefore, in the ninth embodiment, when the coding side performs variable length coding of AC coefficient data in a region using a VLC table selected for each region, the coding should be performed in the VLC table. If there is no code word corresponding to the AC coefficient data, even if the AC coefficient data is converted and multiplexed again into a bit stream including the AC coefficient data encoded by the VLC table, the conversion flag determination unit The conversion of the AC coefficient data on the encoding side is determined by 107b83, and the processing opposite to that on the encoding side is performed in the area data decoding unit 107b8. Therefore, as in the encoding side of the fifth embodiment, Even when an encoded bit stream obtained by converting AC coefficient data using an escape code and multiplexing the same is transmitted, decoding can be performed correctly.

[0188]

As described above, according to the present invention, a block is divided into a plurality of regions, and the VLC is determined for each region in accordance with the position of the region in the block and the encoding conditions at the time of quantization.
Select a table group and select the selected VL
Since the VLC table can be selected from the C table group and the transform coefficient can be subjected to variable length coding, the transform coefficient can be coded with a smaller code amount. In addition, by selecting a VLC table group to be switched in the region based on the position of the region and the encoding conditions at the time of quantization, the amount of code required to encode information indicating the VLC table to be switched is reduced. be able to.

In the next invention, when a VLC table is selected from the selected VLC table group, the VLC table is selected according to the scan position in the area, and as additional information, information indicating the VLC table to be switched Need not be multiplexed into the bit stream, and VL
The effect that the code amount of the additional information required for switching the C table can be reduced is obtained.

Further, in the next invention, it is determined whether or not the quantized transform coefficient in the area is zero for each area. If the coefficient in the area is all zero, it is determined that the area is invalid. For regions where information is encoded and there are non-zero coefficients in the region, the VL used to encode the coefficients
Conventionally, by encoding the information indicating the C table,
The structure of different bit streams can be made common depending on the encoding mode, and an effect is obtained that a circuit for syntax analysis can be simplified in the decoding device.

In the next invention, when performing variable length encoding of AC coefficient data, if there is no data corresponding to the AC coefficient data to be encoded in the VLC table, the AC coefficient data is converted and converted. By searching the VLC table again based on the AC coefficient data and performing variable length coding, an effect of increasing the compression efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a video encoding device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing an internal configuration of a variable length coding unit according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing an internal configuration of a texture encoding unit according to Embodiment 1 of the present invention.

FIG. 4 is an explanatory diagram of variable coefficient prediction according to the first embodiment of the present invention.

FIG. 5 is a block diagram showing an internal configuration of a transform coefficient variable length coding unit 4c according to Embodiment 1 of the present invention.

FIG. 6 is a flowchart showing the operation of the transform coefficient variable length coding unit 4c according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating an area serving as a unit for encoding AC coefficient data according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating a VLC table group according to the first embodiment of the present invention.

FIG. 9 is a block diagram showing an internal configuration of a transform coefficient variable length coding unit 4c according to a second embodiment of the present invention.

FIG. 10 is a block diagram showing an internal configuration of a transform coefficient variable length coding unit 4c according to Embodiment 3 of the present invention.

FIG. 11 is a block diagram showing an internal configuration of a transform coefficient variable length coding unit 4c according to a fourth embodiment of the present invention.

FIG. 12 is a diagram illustrating a macroblock data structure in the conventional MPEG-4.

FIG. 13 is a diagram illustrating a macroblock data structure according to a fourth embodiment of the present invention.

FIG. 14 is a block diagram showing an internal configuration of an area data encoding unit according to Embodiment 5 of the present invention.

FIG. 15 is a block diagram showing a configuration of a video decoding device according to Embodiment 6 of the present invention.

FIG. 16 is a block diagram showing an internal configuration of a variable length decoding unit according to Embodiment 6 of the present invention.

FIG. 17 is a block diagram showing an internal configuration of a transform coefficient variable length decoding unit according to Embodiment 6 of the present invention.

FIG. 18 is a flowchart showing an operation of a transform coefficient variable length decoding unit according to Embodiment 6 of the present invention.

FIG. 19 is a block diagram showing an internal configuration of a texture decoding unit according to Embodiment 6 of the present invention.

FIG. 20 is a block diagram showing an internal configuration of a transform coefficient variable length decoding unit according to Embodiment 7 of the present invention.

FIG. 21 is a block diagram showing an internal configuration of a transform coefficient variable length decoding unit according to Embodiment 8 of the present invention.

FIG. 22 is a block diagram showing an internal configuration of an area data decoding unit according to Embodiment 9 of the present invention.

[Explanation of symbols]

1 input shape data, 2 shape coding units, 3 shape coding data, 4 variable length coding units, 5 multiplexing units, 6 locally decoded shape data, 7 input texture data, 8 intra / inter determination unit, 9 mode instruction Flags, 10
Motion detector, 11 motion vector, 12 motion compensator, 13 predicted image signal, 14 prediction error signal, 15
Encoded image signal, 16 Texture encoding unit, 17
Quantized transform coefficient data, 18 texture local decoding unit,
19 locally decoded prediction error signal, 20 locally decoded image signal,
21 switching unit, 22 reference image signal, 23 memory, 2
4 shape data codeword, 25 additional information codeword, 26 block data codeword, 27 motion vector codeword, 28
Coded bit stream, 29 shape data variable length coding unit, 30 additional information variable length coding unit 4c transform coefficient variable length coding unit 442 motion vector variable length coding unit, 1
6a block data extraction section, 16b block data, 16c DCT section, 16d DCT coefficient, 16e
Quantization unit, 16f quantization conversion coefficient, 16g conversion coefficient prediction unit, 42 conversion coefficient prediction determination information, 43 switching unit,
44 DC coefficient data coding unit, 45 AC coefficient data, 4c5 DC coefficient codeword, 4c6 VLC table group selection unit, 4c7 VLC table group information, 4c8 VLC table selection unit, 4c9 VLC table selection information 107b9, 4c10 Area data coding Section, 4c11 AC coefficient codeword, 26 block data codeword, 54 quantization step size, 55 coding condition, 4c12 area data valid / invalidity determination section, 4c1
3 area valid / invalid information, 4c14 area valid / invalid information coding unit, 4c15 area valid / invalid information codeword, 6
0 VLC table search unit, 4c102 escape code, 4c103 conversion coefficient conversion unit, 4c104 conversion AC coefficient data, 4c105 conversion flag, 4c106
Transform coefficient fixed length decoding unit, 101 encoded bit stream, 102 syntax analysis unit, 103 shape data codeword, 104 block data codeword, 105 additional information codeword, 106 motion vector codeword, 107
Variable length decoding unit, 108 shape encoded data, 109 quantized transform coefficient data, 110 additional information, 111 motion vector, 112 shape decoding unit, 113 texture decoding unit, 114 motion compensation unit, 115 decoded shape data,
116 decoded prediction error signal, 117 memory, 118
Reference picture, 119 Decoded macroblock screen position information, 120 Predicted picture, 121 Decoding adder, 122
Decoded image, 123 switching unit, 110a mode instruction flag, 107a shape data variable length decoding unit, 107b transform coefficient variable length decoding unit, 107c additional information variable length decoding unit, 107d motion vector variable length decoding unit, 107b1
Switching section, 107b2 DC coefficient data decoding section, 107
b3 decoded DC coefficient, 107b4 AC coefficient data codeword, 110b encoding condition, 107b6 VLD table group selector, 107b7 VLD table group information, 107b8 area data decoder, 107b9
VLC table selection information 107b9, 107b10 V
LD table selector, 107b11 VLD table,
107b12 area data decoding unit, 107b12 decoded AC coefficient, 113a switching unit, 110b1 conversion coefficient prediction determination information, 113c conversion coefficient prediction unit, 113d differential quantization conversion coefficient, 113e adjacent block quantization conversion coefficient, 113f quantization conversion coefficient, 113g Inverse quantization unit, 113h quantization step, 113i DCT coefficient, 113j inverse DCT unit, 107b13 position information,
107b area valid / invalid information codeword, 107b14
Area valid / invalid information decoding unit, 107b15 Area valid / invalid
Invalid information, 107b16 area valid / invalid judgment unit, 107
b17 area data zero setting unit, 107b81 VLD table search unit, 107b82 escape code, 10
7b83 Conversion flag determination unit, 107b84 Decoding conversion AC coefficient, 107b85 Conversion coefficient inverse conversion unit, 107b
86 conversion coefficient fixed length decoding unit, 107b87 conversion AC
Coefficient codeword.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kotaro Asai 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Hirofumi Nishikawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd. (72) Shinichi Kuroda, Inventor 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Sanishi Electric Co., Ltd. (72) Yuri Hasegawa 2-3-2, Marunouchi, Chiyoda-ku, Tokyo Mitsuishi F term (reference) in Denki Co., Ltd. 5C059 MA00 MA05 MA23 MB02 MB14 MB16 MC01 MC11 MC32 MC34 MC38 ME01 ME05 ME13 ME15 NN01 NN28 PP04 PP16 RC38 TA47 TA50 TB07 TC04 TC06 TC27 TC42 TD05 UA02 UA05

Claims (18)

[Claims] An input image signal is transformed and quantized in units of blocks to generate quantized transform coefficients, and the quantized transform coefficients are subjected to variable-length coding by a variable-length coding table for each predetermined area in the block. In a moving picture coding apparatus that generates a coded bit stream, a plurality of variable-length coding tables that are grouped in advance, and one variable-length coding table group among the plurality of variable-length coding tables are A variable-length coding table group selecting means for selecting, and using the variable-length coding table of the selected group, the variable-length coding of the quantized transform coefficient is performed, and the variable-length coding table of the selected group is converted. Encoding bit stream generation means for generating an encoded bit stream including information indicating Location. 2. A method according to claim 1, wherein the plurality of variable length coding table groups are grouped in advance based on coding conditions at the time of quantization. 2. The moving picture coding apparatus according to claim 1, wherein a variable length coding table group is selected based on a coding condition. 3. The variable length coding table group includes a plurality of variable length coding tables grouped based on the presence or absence of a transform coefficient prediction for calculating a difference between quantized transform coefficients between blocks. Encoding table group selecting means selects a corresponding variable length encoding table group from the plurality of variable length encoding table groups based on the presence or absence of the transform coefficient prediction, and the encoded bit stream generating means is selected. 2. The moving picture coding apparatus according to claim 1, wherein an encoded bit stream including information indicating the presence / absence of said transform coefficient prediction is generated as information indicating a variable length coding table of said group. 4. A variable-length coding table group includes a plurality of variable-length coding tables grouped according to a quantization step size. And selecting a corresponding variable length coding table group from the plurality of variable length coding table groups based on the plurality of variable length coding table groups. 2. The moving image encoding apparatus according to claim 1, wherein an encoded bit stream including information on an encoding step size is generated. 5. The variable length coding table is switched based on the position of the quantized transform coefficient in the area from among the variable length coding table groups selected by the variable length coding table group selecting means. 2. A variable length coding table switching means, comprising:
5. The moving picture coding apparatus according to any one of claims 1 to 4. 6. The variable-length coding of the quantized transform coefficients, wherein an invalid area means that all quantized transform coefficients in each area are zero, and an effective area means that there is a non-zero coefficient in each area. A region data validity / invalidity determining unit for determining the region; and a coded bit stream generating unit, based on the selected variable length encoding table, when the region data valid / invalidity determining unit determines that the region is valid. While encoding the quantized transform coefficients in the area and generating an encoded bit stream including information indicating the variable length encoding table used at that time, if the area is determined to be an invalid area, the area is determined to be invalid. The moving picture coding apparatus according to claim 1, wherein a coded bit stream including information indicating invalidity is generated. 7. The variable-length coding of a quantized transform coefficient, when a corresponding codeword is not present in a variable-length coding table, the coded bitstream generating means performs quantization without the corresponding codeword. The conversion coefficient is converted to a value included in the variable length coding table by a predetermined method, and the quantized conversion coefficient after the conversion is variable length coded by the variable length table to obtain information indicating the conversion method. The moving picture coding apparatus according to any one of claims 1 to 6, wherein the moving picture coding apparatus generates a coded bit stream including: 8. A coded bit stream is input, and coded data subjected to variable length coding for each block included in the coded bit stream is subjected to variable length decoding to restore a quantized transform coefficient. In a moving picture decoding apparatus for decoding an image signal by inversely quantizing and inversely transforming a quantized transform coefficient, a plurality of variable length decoding tables grouped into groups, and a variable length decoding table used on the encoding side from the encoded bit stream. A variable-length decoding table group selecting unit that decodes information indicating the long-length coding table group and selects a variable-length decoding table group from the variable-length decoding table group based on the variable-length coding table group information; Quantized transform coefficient for restoring the quantized transform coefficient by performing variable length decoding of the encoded data using the variable length decoding table of the selected group A moving image decoding apparatus comprising: a restoration unit. 9. The variable length decoding table group is pre-grouped based on encoding conditions at the time of quantization, and the variable length decoding table group selecting means encodes the encoded bit stream from an encoded bit stream. As information indicating the variable-length coding table group used on the side, information indicating an encoding condition at the time of quantization is decoded, and a variable-length decoding table group is selected based on the encoding condition at the time of quantization. 9. The moving picture decoding apparatus according to claim 8, wherein: 10. The variable-length decoding table group includes a plurality of variable-length decoding tables grouped based on the presence or absence of a transform coefficient prediction for calculating a difference between quantized transform coefficients between blocks. The table group selecting means decodes, from the coded bit stream, information indicating the presence or absence of a quantized transform coefficient prediction as information indicating the variable length coding table group used on the encoding side, and determines whether or not the quantized transform coefficient prediction is performed. 9. The moving picture decoding apparatus according to claim 8, wherein a variable length decoding table group is selected based on information indicating. 11. The variable-length decoding table group includes a plurality of variable-length decoding tables grouped based on a quantization step size, and the variable-length decoding table group selecting unit encodes a variable-length decoding table from an encoded bit stream. As information indicating the variable length coding table group used on the side, decoding the quantization step size, based on the decoded quantization step size,
9. The moving picture decoding apparatus according to claim 8, wherein a variable length decoding table group is selected. 12. The quantized transform coefficient restoring means decodes the quantized transform coefficient by switching a plurality of variable length decoding tables in the variable length decoding table group selected by the variable length decoding table group selecting means. When doing
The moving picture decoding apparatus according to any one of claims 8 to 11, further comprising: a variable length decoding table selecting unit that switches a variable length decoding table based on a position of the quantized transform coefficient in a region. . 13. The quantized transform coefficient restoring means, when all the quantized transform coefficients in the region are zero, indicates that the region is invalid, and there is one or more quantized transform coefficients that are not zero. In this case, the variable length coding table selection information indicating the variable length decoding table used to decode each quantized transform coefficient in the region is decoded, and the region is determined based on the decoded variable length coding table selection information. Determining means for determining whether or not the area is invalid; and quantizing transform coefficient zero setting means for setting all quantized transform coefficients in the area to zero when the area is determined to be invalid by the determining means. The moving picture decoding apparatus according to any one of claims 8 to 12, comprising: 14. A judging means for judging whether or not information indicating that a quantized transform coefficient has been converted by a predetermined method on an encoding side from an encoded bit stream has been decoded, and If it is determined that the information has been decoded, the decoding is performed using the variable-length decoding table when the quantized transform coefficient is restored, and then a process reverse to the conversion of the predetermined method is performed. 14. The moving picture decoding apparatus according to claim 8, further comprising: means for restoring a quantized transform coefficient before transform. 15. A quantized transform coefficient is created by transforming and quantizing an input image signal on a block basis, and the quantized transform coefficient is converted into a variable length code by a variable length coding table defined for each predetermined area in the block. In the moving picture coding method of coding to generate a coded bit stream, a variable length coding table group is selected from a plurality of grouped variable length coding tables, and the variable length of the selected group is selected. A moving image encoding method, comprising: encoding a quantized transform coefficient with a variable length using an encoding table; and generating an encoded bit stream including information indicating the selected variable length encoding table. 16. When selecting a variable length coding table group from a plurality of grouped variable length coding tables, the variable length coding table group is selected based on a coding condition at the time of quantization. 16. The moving image encoding method according to claim 15, wherein an encoded bit stream including information on encoding conditions at the time of the quantization is generated as information indicating a variable length encoding table. 17. A coded bit stream is input, and coded data subjected to variable length coding for each block included in the coded bit stream is subjected to variable length decoding to restore quantized transform coefficients. In a moving picture decoding method for inversely quantizing and inversely transforming a quantized transform coefficient to decode an image signal, when restoring the quantized transform coefficient, the variable-length coding used on the encoding side from the encoded bit stream. Decoding information indicating a table group, selecting a variable length decoding table group from the plurality of grouped variable length decoding table groups based on the variable length coding table group information, and selecting a variable length of the selected group. A moving picture decoding method, characterized in that the encoded data is variable-length decoded using a decoding table to restore the quantized transform coefficients. 18. When restoring a quantized transform coefficient, information of a coding condition at the time of quantization is decoded from the coded bit stream as information indicating a variable length coding table group used on the coding side. 18. The moving picture decoding method according to claim 17, wherein a variable length decoding table group is selected based on information on an encoding condition at the time of the quantization.