JP2021093575A - Coding device, decoding device and program - Google Patents

Abstract

To improve coding efficiency while suppressing reduction in through-put at a decoding device side.SOLUTION: A coding device, which performs coding in a block unit constituting an image, comprises: an intra-prediction part that generates a prediction block corresponding to a block to be coded, by intra-prediction using a decoded pixel around the block to be coded; a conversion/quantization part that performs conversion processing and quantization processing for a prediction residual representing a difference between the block to be coded and the prediction block; an entropy coding part that codes a conversion coefficient which is outputted by the conversion/quantization part; and a scan control part that determines a scan order out of a plurality of candidates for scan orders at the time when the entropy encoding part codes the conversion coefficient, in accordance with syntax indicating an intra-prediction mode used in the intra-prediction. The scan control part determines the scan order directly from the syntax, without specifying the intra-prediction mode from the syntax.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coding device, a decoding device, and a program.

Research is being conducted on video coding methods for compressing the amount of data during transmission and storage of still images and moving images. In recent years, ultra-high resolution images such as 8K-SHV have become widespread, and AVC / H.A. 264 and HEVC / H. Coding methods such as 265 are known.

In the evaluation software (VTM) of VVC, which is a next-generation video coding method jointly standardized by MPEG and ITU, intra-prediction using spatial correlation within a frame is used (for example, non-standardization). See Patent Document 1).

In the intra prediction, the decoded reference pixels around the coded block are used, and the Planar prediction, the DC prediction, and the 65 direction prediction modes are selected from a total of 67 prediction modes, which is the optimum mode on the coding device side. Is selected and the information is sent to the decoding device side.

In addition, since the prediction modes used in the coded block and its peripheral blocks are highly correlated, the prediction modes used in the blocks to the left and above the coded block and the prediction modes in a direction close to those prediction modes are used. It is possible to apply a priority intra-prediction mode (MPM: Most Problem Modes) that prioritizes modes and allocates a relatively small amount of data to other prediction modes.

In HEVC, the scan order indicating the coding and decoding order at the time of binarizing the conversion coefficient is switched according to the intra prediction mode for the coded target block of a predetermined size. Specifically, it is possible to improve the coding efficiency by adaptively switching the scan order by utilizing the statistical bias of the distribution of the prediction residual according to the intra prediction mode.

JVET-O2001 Versatile Video Coding (Draft 6)

As described above, there is a statistical bias in the distribution of the forecast residuals depending on the intra-prediction mode. For example, when the intra prediction mode is a directional prediction mode close to vertical, there is a high possibility that a conversion coefficient of a large value appears at the top of the block. In that case, efficiency is improved by scanning from the bottom to the top of the block with a horizontal scan.

However, in the conventional coding method, when it is necessary to specify the intra-prediction mode at the time of parsing the streaming, the next parsing process cannot be continued at that point, which causes a problem that the throughput on the decoding device side is reduced. is there.

Therefore, an object of the present invention is to provide a coding device, a decoding device, and a program capable of improving the coding efficiency while suppressing the reduction in throughput on the decoding device side.

The coding device according to the first aspect is a coding device that encodes in units of blocks constituting an image, and the coding target block is based on intra-prediction using decoded pixels around the coding target block. An intra-prediction unit that generates a prediction block corresponding to the above, a conversion / quantization unit that performs conversion processing and quantization processing on a prediction residual representing a difference between the coding target block and the prediction block, and the conversion. -When the entropy coding unit encodes the conversion coefficient according to the entropy coding unit that encodes the conversion coefficient output by the quantization unit and the syntax indicating the intra prediction mode used for the intra prediction. The scan control unit includes a scan control unit that determines the scan order from a plurality of scan order candidates, and the scan control unit determines the scan order from the syntax without specifying the intra prediction mode from the syntax. The gist is to make a direct decision.

The decoding device according to the second aspect is a decoding device that decodes in block units constituting an image, and is a coefficient indicating an intra prediction mode used for intra prediction of a block to be decoded by decoding a coded stream. And the entropy decoding unit that outputs the conversion coefficient of the decoding target block, and the scan order when the entropy decoding unit decodes the conversion coefficient is determined from a plurality of scan order candidates according to the syntax. The scan control unit to generate the prediction block corresponding to the decoding target block by the intra prediction using the decoded pixels around the decoding target block, and the conversion coefficient output by the entropy decoding unit. On the other hand, the inverse quantization / inverse conversion unit that performs inverse quantization processing and inverse conversion processing to restore the predicted residual, and the restored predicted residual and the predicted block are combined to restore the decoding target block. The gist is that the scan control unit includes a synthesis unit and directly determines the scan order from the syntax without specifying the intra prediction mode from the syntax.

The gist of the program according to the third aspect is to make the computer function as a coding device according to the first aspect.

The gist of the program according to the fourth aspect is to make the computer function as a decoding device according to the second aspect.

According to the present invention, it is possible to provide a coding device, a decoding device, and a program capable of improving coding efficiency while suppressing a reduction in throughput on the decoding device side.

It is a figure which shows the structure of the coding apparatus which concerns on embodiment. It is a figure which shows the scan order which concerns on embodiment. It is a figure which shows an example of the non-MPM mode number which concerns on embodiment. It is a figure which shows the candidate of the intra prediction mode which concerns on embodiment. It is a figure which shows the association information which concerns on embodiment. It is a figure which shows the structure of the decoding apparatus which concerns on embodiment. It is a figure which shows the operation of the scan control part which concerns on embodiment.

The coding device and the decoding device according to the embodiment will be described with reference to the drawings. The coding device and the decoding device according to the embodiment encode and decode a moving image represented by MPEG, respectively. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals.

<Configuration of coding device>
First, the configuration of the coding apparatus according to the present embodiment will be described. FIG. 1 is a diagram showing a configuration of a coding device 1 according to the present embodiment.

As shown in FIG. 1, the coding device 1 includes a block division unit 100, a subtraction unit 110, a conversion / quantization unit 120, an entropy coding unit 130, a scan control unit 131, and an inverse quantization / inverse. It has a conversion unit 140, a synthesis unit 150, a memory 160, and a prediction unit 170.

The block division unit 100 divides an original image, which is an input image for each frame (or picture) constituting a moving image, into a plurality of image blocks, and outputs the image block obtained by the division to the subtraction unit 110. The size of the image block is, for example, 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, 4 × 4 pixels, or the like. The shape of the image block is not limited to a square and may be a rectangle (non-square). The image block is a unit for coding by the coding device 1 (that is, a block to be coded) and a unit for decoding by the decoding device (that is, a block to be decoded). Such an image block is sometimes called a CU (Coding Unit).

For example, the block division unit 100 outputs a luminance block and a luminance block by performing block partitioning on the luminance signal and the color difference signal constituting the image. The division may be independently controllable for the luminance signal and the color difference signal. When the luminance block and the color difference block are not particularly distinguished, they are simply referred to as a coded block.

The subtraction unit 110 calculates a prediction residual representing a difference (error) between the coding target block output from the block division unit 100 and the prediction block obtained by predicting the coding target block by the prediction unit 170. Specifically, the subtraction unit 110 calculates the prediction residual by subtracting each pixel value of the prediction block from each pixel value of the block, and outputs the calculated prediction residual to the conversion / quantization unit 120.

The conversion / quantization unit 120 performs conversion processing and quantization processing on a block-by-block basis. The conversion / quantization unit 120 includes a conversion unit 121 and a quantization unit 122.

The conversion unit 121 performs conversion processing on the predicted residual output from the subtraction unit 110 to calculate a conversion coefficient, and outputs the calculated conversion coefficient to the quantization unit 122. The conversion process refers to, for example, the discrete cosine transform (DCT), the discrete sine transform (DST), the carunen-reve transform (KLT), and the like. However, the conversion process may include a conversion skip that adjusts by scaling or the like without converting the signal in the pixel region into the signal in the frequency domain. The conversion unit 121 outputs information regarding the conversion process applied to the coded target block to the entropy coding unit 130.

The conversion unit 121 may use an MTS that switches a plurality of conversion bases in coding the luminance signal. Specifically, the conversion unit 121 may apply a conversion basis (conversion type) selected from DCT-2, DST-7, and DCT-8 in each of the horizontal direction and the vertical direction.

The quantization unit 122 quantizes the conversion coefficient output from the conversion unit 121 using the quantization parameter (Qp) and the quantization matrix, and the quantized conversion coefficient is the entropy coding unit 130 and the inverse quantization / inverse conversion. Output to unit 140.

The entropy coding unit 130 performs entropy coding on the conversion coefficient output from the quantization unit 122, performs data compression to generate coded data (bit stream), and encodes the coded data in the coding device 1. Output to the outside of. For the entropy coding, a Huffman code, a CABAC (Context-based Adaptive Binary Arithmetic Coding; context-adaptive binary arithmetic code) or the like can be used.

Specifically, the entropy coding unit 130 reads out the conversion coefficients arranged in two dimensions in a predetermined scan order and encodes them in subblock units. FIG. 2 is a diagram showing a scan order according to the present embodiment.

In FIG. 2, the coded block has a size of 8 pixels in the horizontal direction and 8 pixels in the vertical direction (that is, 8 × 8 pixels), and each subblock SB1 to SB4 has 4 pixels in the horizontal direction and 8 pixels in the vertical direction. An example having a size of 4 pixels (that is, 4 × 4 pixels) is shown.

As shown in FIG. 2, there are three scan order candidates: diagonal scan, vertical scan, and horizontal scan. As shown in FIG. 2A, the oblique scanning is a scanning order in which scanning is performed obliquely from the high frequency side to the low frequency side in each subblock. As shown in FIG. 2B, the vertical scan is a scan order in which scanning is performed in the vertical direction from the high frequency side to the low frequency side in each subblock. As shown in FIG. 2C, the horizontal scan is a scan order in which scanning is performed in the horizontal direction from the high frequency side to the low frequency side in each subblock.

In addition to such conversion coefficient scanning processing and coding processing, the entropy coding unit 130 encodes information related to the conversion processing output from the conversion unit 121 and information related to the prediction processing output from the prediction unit 170. Is also coded.

Here, the information regarding the prediction process includes a syntax indicating the intra prediction mode used by the prediction unit 170 for the intra prediction of the coded block (hereinafter, referred to as “intra prediction mode syntax”). Intra-prediction mode syntax indicating the intra-prediction mode for the luminance block includes, for example, intra_luma_mpm_flag, intra_luma_not_planar_flag, intra_luma_mpm_idx, and intra_luma_mpm_reminder.

The intra_luma_mpm_flag is a flag indicating whether or not the intra prediction mode used for the intra prediction is included in a plurality of priority intra prediction modes (hereinafter, referred to as “MPM mode”). When intra_luma_mpm_flag is "1", it indicates that the intra prediction mode is included in the MPM mode. On the other hand, when intra_luma_mpm_flag is "0", the intra prediction mode is not included in the MPM mode, that is, the intra prediction mode is included in a plurality of non-priority intra prediction modes (hereinafter, referred to as "non-MPM mode"). Is shown.

intra_luma_not_planar_flag is a flag indicating whether or not the intra prediction mode is Planar mode when intra_luma_mpm_flag is "1". When intra_luma_not_planar_flag is "1", it indicates that the intra prediction mode is not Planar mode. On the other hand, when intra_luma_not_planar_flag is "0", it indicates that the intra prediction mode is Planar mode.

intra_luma_mpm_idx is an index indicating the number of the MPM in the intra prediction mode when intra_luma_not_planar_flag is "1". Intra_luma_mpm_idx indicates any number from MPM1 to MPM5 using Truncated Unary encoding.

intra_luma_mpm_reminder is a non-MPM mode number indicating any of the non-MPM intra-prediction modes when intra_luma_mpm_flag is "0". FIG. 3 is a diagram showing an example of a non-MPM mode number according to the present embodiment.

As shown in FIG. 3, intra_luma_mpm_reminder indicates any number in 61 modes using Tunnelated binary encoding. In this 61 mode, 61 intra prediction modes other than the MPM mode are assigned in ascending order from the lower left to the upper right in the reference direction.

The scan control unit 131 controls the scan order when the entropy coding unit 130 encodes the conversion coefficient. Specifically, the scan control unit 131 determines the scan order from a plurality of scan order candidates according to the intra-prediction mode syntax indicating the intra-prediction mode used for the intra-prediction of the coded block, and determines the scan order. The entropy coding unit 130 is controlled according to the scanning order. In the present embodiment, as shown in FIG. 2, the plurality of scan order candidates are three, an oblique scan, a vertical scan, and a horizontal scan. The details of the scan control unit 131 will be described later.

The inverse quantization / inverse transformation unit 140 performs the inverse quantization process and the inverse transformation process on a block-by-block basis. The inverse quantization / inverse conversion unit 140 includes an inverse quantization unit 141 and an inverse conversion unit 142.

The inverse quantization unit 141 performs an inverse quantization process corresponding to the quantization process performed by the quantization unit 122. Specifically, the inverse quantization unit 141 restores and restores the conversion coefficient by inversely quantizing the conversion coefficient output from the quantization unit 122 using the quantization parameter (Qp) and the quantization matrix. The converted conversion coefficient is output to the inverse conversion unit 142.

The inverse conversion unit 142 performs an inverse conversion process corresponding to the conversion process performed by the conversion unit 121. For example, when the conversion unit 121 performs the discrete cosine transform, the inverse transform unit 142 performs the inverse discrete cosine transform. The inverse transformation unit 142 performs an inverse transformation process on the conversion coefficient output from the inverse quantization unit 141 to restore the predicted residual, and outputs the restored predicted residual, which is the restored predicted residual, to the synthesis unit 150. To do.

The synthesizing unit 150 synthesizes the restoration prediction residual output from the inverse conversion unit 142 with the prediction block output from the prediction unit 170 on a pixel-by-pixel basis. The synthesizing unit 150 adds each pixel value of the restoration prediction residual and each pixel value of the prediction block to decode (reconstruct) the coded block, and outputs the decoded block to the memory 160. The decrypted block is sometimes called a reconstructed block.

The memory 160 stores the decoded blocks output from the compositing unit 150, and stores the decoded blocks as a decoded image in frame units. The memory 160 outputs the stored decoded block or decoded image to the prediction unit 170. A loop filter may be provided between the compositing unit 150 and the memory 160.

The prediction unit 170 performs prediction processing in block units. The prediction unit 170 includes an inter-prediction unit 171, an intra-prediction unit 172, and a switching unit 173.

The inter-prediction unit 171 performs inter-prediction using the correlation between frames. Specifically, the inter-prediction unit 171 uses the decoded image stored in the memory 160 as a reference image, calculates a motion vector by a method such as block matching, predicts the target block of inter-prediction, and inter-predicts. A block is generated, and the generated inter-prediction block is output to the switching unit 173. Here, the inter-prediction unit 171 selects the optimum inter-prediction method from inter-prediction using a plurality of reference images (typically bi-prediction) and inter-prediction using one reference image (one-way prediction). Select and perform inter-prediction using the selected inter-prediction method. The inter-prediction unit 171 outputs information (motion vector, etc.) related to the inter-prediction to the entropy coding unit 130.

The intra prediction unit 172 performs intra prediction using the spatial correlation in the frame. Specifically, the intra prediction unit 172 generates an intra prediction block by referring to the decoded pixels around the target block of the intra prediction among the decoded images stored in the memory 160, and generates the intra prediction. The block is output to the switching unit 173. The intra prediction unit 172 selects an intra prediction mode to be applied to the target block of the intra prediction from the plurality of intra prediction modes, and predicts the target block using the selected intra prediction mode. The intra prediction unit 172 outputs the intra prediction mode syntax indicating the selected intra prediction mode to the entropy coding unit 130.

FIG. 4 is a diagram showing candidates for the intra prediction mode according to the present embodiment. As shown in FIG. 4, there are 67 candidates for the intra prediction mode for the luminance block from 0 to 66. The mode "0" of the intra prediction mode is Planar prediction, the mode "1" of the intra prediction mode is DC prediction, and the modes "2" to "66" of the intra prediction mode are directional prediction. In the directionality prediction, the direction of the arrow indicates the reference direction, the starting point of the arrow indicates the position of the pixel to be predicted, and the end point of the arrow indicates the position of the reference pixel used to predict the pixel to be predicted. As reference directions parallel to the diagonal line passing through the upper right and lower left vertices of the block, there are an intra prediction mode "2" that refers to the lower left direction and a mode "66" that is an intra prediction mode that refers to the upper right direction. , Mode numbers are assigned to each predetermined angle clockwise from the mode "2" to the mode "66".

The switching unit 173 switches between the inter prediction block output from the inter prediction unit 171 and the intra prediction block output from the intra prediction unit 172, and outputs one of the prediction blocks to the subtraction unit 110 and the synthesis unit 150.

As described above, the coding apparatus 1 according to the present embodiment has an intra prediction unit 172 that generates a prediction block corresponding to the code target block by intra prediction using decoded pixels around the code target block, and a code. A conversion / quantization unit 120 that performs conversion processing and quantization processing on the prediction residual that represents the difference between the conversion target block and the prediction block, and an entropy code that encodes the conversion coefficient output by the conversion / quantization unit 120. The scan order when the entropy coding unit 130 encodes the conversion coefficient is determined from a plurality of scan order candidates according to the quantization unit 130 and the intra prediction mode syntax indicating the intra prediction mode used for the intra prediction. It has a scan control unit 131 and a scan control unit 131.

In the present embodiment, the coding apparatus 1 prioritizes the prediction modes used in the blocks to the left and above the blocks to be coded and the prediction modes in the direction close to those prediction modes, and gives priority to other prediction modes. MPM that allocates a relatively small amount of data to is applied.

Specifically, the intra prediction unit 172 according to the present embodiment includes an MPM determination unit 1721 and a syntax generation unit 1722. The MPM determination unit 1721 corresponds to the priority mode determination unit.

The MPM determination unit 1721 has a plurality of priority intra prediction modes (MPM mode) that are preferentially applied to the coded target block and a plurality of priorities based on the intra prediction mode applied to the blocks surrounding the coded target block. A plurality of non-priority intra-prediction modes (non-MPM modes) other than the intra-prediction mode are determined. The MPM determination unit 1721 generates a list consisting of the determined MPM modes. Such a list is sometimes referred to as an MPM list. For example, the MPM list consists of six preferred intra-prediction modes.

The syntax generation unit 1722 generates an intra prediction mode syntax indicating the intra prediction mode used by the intra prediction unit 172 for the intra prediction of the coded block, and uses the generated intra prediction mode syntax as the entropy coding unit 130 and the entropy coding unit 130. Output to the scan control unit 131. As mentioned above, the intra-prediction mode syntax indicating the intra-prediction mode for the luminance block includes intra_luma_mpm_flag, intra_luma_not_planar_flag, intra_luma_mpm_idx, and intra_luma_mpm_reminder.

In particular, the syntax generation unit 1722 generates an intra-prediction mode syntax having intra_luma_mpm_flag, which is a flag indicating whether the intra-prediction mode used for intra-prediction is included in the MPM mode or the non-MPM mode. Further, when the intra-prediction mode used for the intra-prediction is included in the non-MPM mode, the syntax generation unit 1722 further includes the intra-prediction mode thin, which is a non-MPM mode number indicating the intra-prediction mode used for the intra-prediction. Generate tax.

In the present embodiment, the scan control unit 131 determines the scan order from a plurality of scan order candidates according to the intra-prediction mode syntax indicating the intra-prediction mode used for the intra-prediction of the coded block. Here, the scan control unit 131 directly determines the scan order from the intra prediction mode syntax indicating the intra prediction mode without specifying the intra prediction mode from the intra prediction mode syntax indicating the intra prediction mode.

Specifically, the scan control unit 131 indicates an intra prediction mode when the intra_luma_mpm_flag indicates that the intra prediction mode used for the intra prediction is included in the non-MPM mode, that is, when the intra_luma_mpm_flag is “0”. The scan order is determined directly from the prediction mode syntax.

For example, when intra_luma_mpm_flag indicates that the intra prediction mode used for intra prediction is included in the non-MPM mode, the scan control unit 131 uses the associative information for associating each non-MPM mode number with the scan order candidate to perform intra prediction. The scan order candidate corresponding to the non-MPM mode number (intra_luma_mpm_reminder) included in the intra prediction mode syntax indicating the mode is determined as the scan order.

FIG. 5 is a diagram showing association information according to the present embodiment.

As shown in FIG. 5, 61 non-MPM modes (non-MPM modes) other than the 6 MPM modes are assigned numbers in ascending order from the lower left to the upper right in the reference direction. A scan order candidate (scan) is associated with each non-MPM mode number.

Specifically, the non-MPM mode numbers are grouped into first to third groups. The first group is a directional prediction mode, and is a group associated with an intra prediction mode in which the prediction direction is closer to the horizontal direction than the vertical direction. The second group is a directional prediction mode, and is a group associated with an intra prediction mode in which the prediction direction is closer to the vertical direction than the horizontal direction. The third group is a group other than the first group and the second group.

In FIG. 5, the non-MPM mode numbers “9” to “20” correspond to the first group, the non-MPM mode numbers “39” to “52” correspond to the second group, and the other non-MPM mode numbers correspond to the first group. Corresponds to the third group. As for the association information, the first group is associated with the vertical scan (scan = 1), the second group is associated with the vertical scan (scan = 2), and the third group is associated with the diagonal scan (scan = 0). Correspond.

Here, no matter what intra prediction mode is selected as the MPM mode, the range is set so that the non-MPM mode that is close to the horizontal direction or the vertical direction to some extent is included in scan = 1 or scan = 2. Further, this range is not fixed to the example shown in FIG. 5, and the range is variable.

When intra_luma_mpm_flag indicates that the intra prediction mode is included in the non-MPM mode, the scan control unit 131 uses the table (correspondence information) as shown in FIG. 5 to use the non-MPM mode included in the intra prediction mode syntax. Since the number (intra_luma_mpm_reminder) can be converted into a scan order number (any of "0", "1", and "2"), the scan order can be directly determined from the non-MPM mode number.

<Configuration of decoding device>
Next, the configuration of the decoding device according to the present embodiment will be mainly described as being different from the coding device 1. FIG. 6 is a diagram showing a configuration of a decoding device 2 according to the present embodiment.

As shown in FIG. 6, the decoding device 2 includes an entropy decoding unit 200, a scan control unit 201, an inverse quantization / inverse conversion unit 210, a synthesis unit 220, a memory 230, and a prediction unit 240.

The entropy decoding unit 200 parses the coded data generated by the coding device 1, acquires the intra prediction mode syntax indicating the intra prediction mode used by the coding device 1 for the intra prediction, and acquires the acquired intra prediction. The mode syntax is output to the scan control unit 201 and the prediction unit 240. Luminance Blocks Intra Prediction Mode Syntax includes intra_luma_mpm_flag, intra_luma_not_planar_flag, intra_luma_mpm_idx, and intra_luma_mpm_reminder.

In decoding the intra prediction mode syntax, the entropy decoding unit 200 decodes the intra_luma_mpm_flag, and in the case of “1”, decodes the intra_luma_not_planar_flag indicating whether or not the intra prediction mode is the Planar mode. When intra_luma_not_planar_flag is "0", the Planar mode is specified as the intra prediction mode. Further, when the intra_luma_not_planar_flag is "1", the entropy decoding unit 200 next decodes the intra_luma_mpm_idx and identifies the number of the MPM. On the other hand, when the entropy decoding unit 200 is "0", the entropy decoding unit 200 decodes the intra_luma_mpm_reminder and identifies which intra prediction mode is not included in the MPM.

Further, the entropy decoding unit 200 acquires information related to the conversion process and outputs the acquired information to the inverse quantization / inverse conversion unit 210.

Further, the entropy decoding unit 200 performs a scanning process according to the scanning order in the multi-valued conversion processing of the conversion coefficient after the arithmetic decoding processing on the coded data is performed, so that the conversion coefficient corresponding to the decoding target block ( Specifically, the quantized conversion coefficient) is output to the inverse quantization / inverse conversion unit 210.

The scan control unit 201 determines the scan order when the entropy decoding unit 200 decodes the conversion coefficient from the plurality of scan order candidates according to the intra prediction mode syntax output from the entropy decoding unit 200. Specifically, the scan control unit 201 determines the scan order from a plurality of scan order candidates according to the intra prediction mode syntax to be used for the intra prediction of the block to be decoded, and the entropy code according to the determined scan order. Controls the conversion unit 130. As described above, there are three scan order candidates: diagonal scan, vertical scan, and horizontal scan. Details of the scan control unit 201 will be described later.

The inverse quantization / inverse transformation unit 210 performs the inverse quantization process and the inverse transformation process on a block-by-block basis. The inverse quantization / inverse conversion unit 210 includes an inverse quantization unit 211 and an inverse conversion unit 212.

The inverse quantization unit 211 performs an inverse quantization process corresponding to the quantization process performed by the quantization unit 122 of the coding apparatus 1. The inverse quantization unit 211 restores the conversion coefficient of the decoding target block by inversely quantizing the quantization conversion coefficient output from the entropy decoding unit 200 using the quantization parameter (Qp) and the quantization matrix. , The restored conversion coefficient is output to the inverse conversion unit 212.

The inverse conversion unit 212 performs an inverse conversion process corresponding to the conversion process performed by the conversion unit 121 of the coding apparatus 1. The inverse conversion unit 212 performs inverse transformation processing on the conversion coefficient output from the inverse quantization unit 211 to restore the predicted residual, and outputs the restored predicted residual (restored predicted residual) to the synthesis unit 220. To do.

The synthesis unit 220 decodes (reconstructs) the original block by synthesizing the prediction residual output from the inverse conversion unit 212 and the prediction block output from the prediction unit 240 on a pixel-by-pixel basis, and has already been decoded. The block is output to the memory 230.

The memory 230 stores the decoded blocks output from the compositing unit 220, and stores the decoded blocks as a decoded image in frame units. The memory 230 outputs the decoded block or the decoded image to the prediction unit 240. Further, the memory 230 outputs the decoded image in frame units to the outside of the decoding device 2. A loop filter may be provided between the compositing unit 220 and the memory 230.

The prediction unit 240 makes a prediction in block units. The prediction unit 240 has an inter prediction unit 241, an intra prediction unit 242, and a switching unit 243.

The inter-prediction unit 241 performs inter-prediction using the correlation between frames. Specifically, the inter-prediction unit 241 uses the decoded image stored in the memory 230 as a reference image based on the inter-prediction information (for example, motion vector information) output from the entropy decoding unit 200. The target block for prediction is predicted, an inter-prediction block is generated, and the generated inter-prediction block is output to the switching unit 243.

The intra prediction unit 242 performs intra prediction using the spatial correlation in the frame. Specifically, the intra-prediction unit 242 uses the intra-prediction mode corresponding to the information regarding the intra-prediction output from the entropy decoding unit 200 (that is, the intra-prediction mode syntax), and has been decoded stored in the memory 230. The intra-prediction block is generated by referring to the decoded pixels around the target block of the intra-prediction in the image, and the generated intra-prediction block is output to the switching unit 243.

In the present embodiment, the decoding device 2 prioritizes the prediction modes used in the blocks to the left and above the blocks to be encoded and the prediction modes in the direction close to those prediction modes, and sets them to other prediction modes. An MPM that allocates a relatively small amount of data is applied.

Specifically, the intra prediction unit 242 according to the present embodiment has an MPM determination unit 2421. The MPM determination unit 2421 corresponds to the priority mode determination unit.

The MPM determination unit 2421 determines an MPM mode preferentially applied to the decoding target block and a non-MPM mode other than the MPM mode based on the intra prediction mode applied to the blocks around the decoding target block. The MPM determination unit 2421 generates a list (MPM list) consisting of the determined MPM modes. For example, the MPM list consists of six preferred intra-prediction modes.

The intra prediction unit 242 specifies the Planar mode as the intra prediction mode when the intra_luma_mpm_flag is “1” and the intra_luma_not_planar_flag is “0”. Further, when the intra_luma_not_planar_flag is "1", the intra prediction unit 242 next decodes the intra_luma_mpm_idx and identifies the number of the MPM determined by the MPM determination unit 2421. On the other hand, when the intra_luma_mpm_flag is "0", the intra prediction unit 242 identifies which intra prediction mode is not included in the MPM based on the intra_luma_mpm_reminder.

The switching unit 243 switches between the inter prediction block output from the inter prediction unit 241 and the intra prediction block output from the intra prediction unit 242, and outputs one of the prediction blocks to the synthesis unit 220.

As described above, the decoding device 2 according to the present embodiment has the intra prediction mode syntax indicating the intra prediction mode used for the intra prediction of the decoding target block by decoding the coded stream, and the conversion coefficient of the decoding target block. The entropy decoding unit 200 that outputs the above, the scan control unit 201 that determines the scan order when the entropy decoding unit 200 decodes the conversion coefficient from a plurality of scan order candidates according to the intra prediction mode syntax, and the decoding. Intra-quantization processing and inverse conversion with respect to the conversion coefficient output by the intra-prediction unit 242 that generates the prediction block corresponding to the decoding target block and the entropy decoding unit 200 by intra-prediction using the decoded pixels around the target block. It has an inverse quantization / inverse conversion unit 210 that performs processing to restore the predicted residual, and a synthesis unit 220 that synthesizes the restored predicted residual and the predicted block to restore the decoding target block.

In the present embodiment, the scan control unit 201 directly orders the scan order from the intra-prediction mode syntax without specifying the intra-prediction mode from the intra-prediction mode syntax in the same manner as the scan control unit 131 of the coding device 1. To decide.

Specifically, the scan control unit 201 indicates an intra prediction mode when the intra_luma_mpm_flag indicates that the intra prediction mode to be used for the intra prediction is included in the non-MPM mode, that is, when the intra_luma_mpm_flag is “0”. The scan order is determined directly from the prediction mode syntax.

For example, when intra_luma_mpm_flag indicates that the intra prediction mode to be used for intra prediction is included in the non-MPM mode, the scan control unit 201 provides association information (see FIG. 5) for associating each non-MPM mode number with the scan order candidate. The scan order candidate corresponding to the non-MPM mode number (intra_luma_mpm_reminder) included in the intra prediction mode syntax indicating the intra prediction mode is determined as the scan order. Since the scan control unit 201 can convert the non-MPM mode number (intra_luma_mpm_reminder) into a scan order number (any of "0", "1", and "2"), the scan order can be directly changed from the non-MPM mode number. Can be decided.

As a result, the scan control unit 201 can adaptively switch the scan order in the entropy decoding unit 200 simply by parsing the intra prediction mode syntax. In other words, the scanning process can be started without waiting for the intra prediction mode to be specified by the decoding process for the intra prediction mode syntax. Therefore, it is possible to improve the coding efficiency while suppressing the reduction in the throughput on the decoding device 2 side.

<Operation of scan control unit>
Next, the operations of the scan control units 131 and 201 according to the present embodiment will be described. Since the scan control units 131 and 201 perform the same operation, the operation of the scan control unit 201 will be described here as an example. FIG. 7 is a diagram showing the operation of the scan control unit 201 according to the present embodiment.

As shown in FIG. 7, in step S1, the scan control unit 201 determines whether the intra_luma_mpm_flag included in the intra prediction mode syntax output by the entropy decoding unit 200 is “0” or “1”. ..

When intra_luma_mpm_flag is "0" (step S1: YES), in step S2, the scan control unit 201 includes the intra_luma_mpm_reminder included in the intra prediction mode syntax output by the entropy decoding unit 200, and a table as shown in FIG. Based on, the scan order is directly determined.

Specifically, the scan control unit 201 directly determines the scan order from the intra_luma_mpm_reminder by converting the intra_luma_mpm_reminder into a scan order number (any of "0", "1", and "2"). When the scan order is determined, the scan control unit 201 controls the entropy decoding unit 200 so as to perform processing in the determined scan order.

<Other Embodiments>
A program that causes a computer to execute each process performed by the coding device 1 may be provided. A program that causes a computer to execute each process performed by the decoding device 2 may be provided. The program may be recorded on a computer-readable medium. Computer-readable media allow you to install programs on your computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

A circuit that executes each process performed by the coding device 1 may be integrated, and the coding device 1 may be configured by a semiconductor integrated circuit (chipset, SoC). A circuit that executes each process performed by the decoding device 2 may be integrated, and the decoding device 2 may be configured by a semiconductor integrated circuit (chipset, SoC).

Although the embodiments have been described in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like can be made within a range that does not deviate from the gist.

1: Coding device 2: Decoding device 100: Block division unit 110: Subtraction unit 120: Conversion / quantization unit 121: Conversion unit 122: Quantization unit 130: Entropy coding unit 131: Scan control unit 140: Inverse quantization Inverse conversion unit 141: Inverse quantization unit 142: Inverse conversion unit 150: Synthesis unit 160: Memory 170: Prediction unit 171: Inter-prediction unit 172: Intra-prediction unit 173: Switching unit 200: Entropy decoding unit 201: Scan control unit 210: Inverse quantization / inverse conversion unit 211: Inverse quantization unit 212: Inverse conversion unit 220: Synthesis unit 230: Memory 240: Prediction unit 241: Inter prediction unit 242: Intra prediction unit 243: Switching unit 1721: MPM determination unit 1722: Syntax generation unit 2421: MPM determination unit

Claims (8)

A coding device that encodes in block units that make up an image.
An intra prediction unit that generates a prediction block corresponding to the code target block by intra prediction using decoded pixels around the code target block, and an intra prediction unit.
A conversion / quantization unit that performs conversion processing and quantization processing on the prediction residual that represents the difference between the coded block and the prediction block.
An entropy coding unit that encodes the conversion coefficient output by the conversion / quantization unit, and
A scan control unit that determines the scan order when the entropy coding unit encodes the conversion coefficient from a plurality of scan order candidates according to the syntax indicating the intra prediction mode used for the intra prediction. With
The scanning control unit is a coding device that directly determines the scanning order from the syntax without specifying the intra prediction mode from the syntax. The intra prediction unit
Based on the intra prediction mode applied to the blocks surrounding the coded target block, a plurality of priority intra prediction modes preferentially applied to the coded target block, and a plurality of priority intra prediction modes other than the plurality of priority intra prediction modes. Priority mode determination unit that determines the non-priority intra prediction mode,
A syntax generation unit that generates the syntax having a flag indicating whether the intra prediction mode used for the intra prediction is included in the plurality of priority intra prediction modes or the plurality of non-priority intra prediction modes. Have and
When the flag indicates that the intra prediction mode used for the intra prediction is included in the plurality of non-priority intra prediction modes, the scan control unit directly determines the scan order from the syntax. The coding apparatus according to claim 1. When the intra prediction mode used for the intra prediction is included in the plurality of non-priority intra prediction modes, the syntax generation unit further includes a non-priority intra prediction mode number indicating the intra prediction mode used for the intra prediction. Generate the syntax and
When the flag indicates that the intra prediction mode used for the intra prediction is included in the plurality of non-priority intra prediction modes, the scan control unit associates each non-priority intra prediction mode number with the scan order candidate. The coding apparatus according to claim 2, wherein a scan order candidate corresponding to the non-priority intra-prediction mode number included in the syntax is determined as the scan order by using the information. A decoding device that decodes each block that constitutes an image.
A syntax indicating an intra prediction mode used for intra prediction of a block to be decoded by decoding a coded stream, an entropy decoding unit that outputs a conversion coefficient of the block to be decoded, and an entropy decoding unit.
A scan control unit that determines the scan order when the entropy decoding unit decodes the conversion coefficient from a plurality of scan order candidates according to the syntax.
An intra prediction unit that generates a prediction block corresponding to the decoding target block by intra prediction using the decoded pixels around the decoding target block, and an intra prediction unit.
An inverse quantization / inverse transformation unit that restores the predicted residuals by performing inverse quantization processing and inverse transformation processing on the conversion coefficient output by the entropy decoding unit.
A synthesis unit for synthesizing the restored predicted residual and the predicted block to restore the decoding target block is provided.
The scanning control unit is a decoding device characterized in that the scanning order is directly determined from the syntax without specifying the intra prediction mode from the syntax. The intra prediction unit has a plurality of priority intra prediction modes that are preferentially applied to the code target block and a plurality of priority intra prediction modes that are preferentially applied to the code target block based on the intra prediction modes applied to the blocks surrounding the code target block. It has a priority mode determination unit that determines a plurality of non-priority intra-prediction modes other than the prediction mode.
The syntax has a flag indicating whether the intra prediction mode used for the intra prediction of the decryption target block is included in the plurality of priority intra prediction modes or the plurality of non-priority intra prediction modes.
When the flag indicates that the intra prediction mode used for the intra prediction of the decryption target block is included in the plurality of non-priority intra prediction modes, the scan control unit directly determines the scan order from the syntax. The decoding device according to claim 4, wherein the decoding apparatus is used. The syntax further has a non-priority intra-prediction mode number indicating the intra-prediction mode used for the intra-prediction when the intra-prediction mode used for the intra-prediction of the decryption target block is included in the plurality of non-priority intra-prediction modes. And
When the flag indicates that the intra prediction mode used for the intra prediction is included in the plurality of non-priority intra prediction modes, the scan control unit associates each non-priority intra prediction mode number with the scan order candidate. The decoding device according to claim 5, wherein a scan order candidate corresponding to the non-priority intra-prediction mode number included in the syntax is determined as the scan order. A program characterized in that a computer functions as the coding device according to any one of claims 1 to 3. A program characterized in that a computer functions as the decoding device according to any one of claims 4 to 6.

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