JP2021093574A - Coding device, decoding device and program - Google Patents

Abstract

To provide a coding device that can be improved in efficiency of coding a last significant coefficient coordinate (a last position) included in a conversion coefficient, a decoding device and a program.SOLUTION: A coding device 1 that 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 120 that performs conversion processing and quantization processing to a prediction residual in the block unit representing a difference between the block to be coded and the prediction block; and an entropy coding part that codes a conversion coefficient in the block unit which is outputted by the conversion/quantization part. The entropy coding part has a coding control part that determines a binarization method that is applied in binarizing a last significant coefficient coordinate indicating a position of a last significant coefficient included in the conversion coefficient, on the basis of an intra-prediction mode used in the intra-prediction.SELECTED DRAWING: Figure 1

Description

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

In the coding method represented by HEVC (High Efficiency Video Coding), it is said that the predicted residual obtained by the difference between the predicted image and the original image by inter-prediction or intra-prediction generally tends to concentrate energy on low frequency components. By utilizing the property and decomposing (converting) the predicted residual into frequency components by conversion processing, reduction of entropy is realized (see, for example, Non-Patent Document 1).

The upper left component of the conversion coefficient obtained by performing the conversion process on the predicted residual is the DC (Direct Current) component, with the higher frequency component in the vertical direction going down and the horizontal direction going to the right. Represents the high frequency component of. Since the coding device outputs the predicted residual as a stream, the position and value of the significance coefficient, which is a significant component of the conversion coefficient after quantization, are entropy-coded and transmitted. The significance coefficient means a conversion coefficient (non-zero coefficient) that is not zero.

The coding device serializes the conversion coefficient in the block from high frequency to low frequency according to the scan order representing the coding order, and entropy encodes the serialized conversion coefficient. At that time, the final significance coefficient coordinates (last position) indicating the position of the last significance coefficient on the highest frequency side of the serialized conversion coefficients are transmitted, and the position and value of the significance coefficient from the last position to the DC component are made efficient. Coordinated.

In HEVC, the scanning order at the time of binarizing the conversion coefficient is switched according to the intra prediction mode. Specifically, the coding efficiency is improved by adaptively switching the scan order by utilizing the statistical bias of the distribution of the prediction residual according to the intra prediction mode.

Further, in HEVC, in the entropy coding of the last position, the two values (last_sig_coeff_x, last_sig_coeff_y), which are the coordinates (relative positions with respect to the DC component) in the block of the last position, are separately entropy-coded. To do. Since the predicted residual generally tends to concentrate energy on the low frequency component, the last position is likely to occur in the upper left region of the conversion coefficient. Therefore, when binarizing to transmit last_sig_coeff_x and last_sig_coeff_y, the last position is efficiently encoded by allocating a small number of bits to a small value and a large number of bits to a large value. There is.

Recognition ITU-T H. 265, (12/2016), “High efficiency video coding”, International Telecommunication Union

As described above, there is a statistical bias in the distribution of the forecast residuals depending on the intra-prediction mode. In other words, the region where the probability that the value of the conversion coefficient becomes large changes 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 upper part of the block.

Similarly, it is considered that the position where the last position appears also changes depending on the intra prediction mode. For example, when the intra prediction mode is a directional prediction mode that is close to vertical, there is a high possibility that the last position will appear at the top of the block. However, in the conventional coding method, since the binarization for transmitting the last position is not controlled according to the intra-prediction mode, there is a problem that the coding efficiency of the last position is poor.

Therefore, an object of the present invention is to provide a coding device, a decoding device, and a program for improving the efficiency of coding the last position.

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, and a conversion / quantization unit that performs conversion processing and quantization processing on the prediction residual in block units representing the difference between the coding target block and the prediction block. , The entropy coding unit that encodes the conversion coefficient of each block output by the conversion / quantization unit, and the entropy coding unit is based on the intra prediction mode used for the intra prediction. The gist is to have a coding control unit that determines the binarization method applied to the binarization of the final significance coefficient coordinates that indicate the position of the final significance coefficient included in the coefficient.

The decoding device according to the second aspect is a decoding device that decodes in block units constituting an image, and is a prediction block corresponding to the decoding target block by intra-prediction using decoded pixels around the decoding target block. The intra-prediction unit that generates the above, the entropy decoding unit that outputs the conversion coefficient of the decoding target block by decoding the coded stream, and the dequantization processing and the inverse quantization processing for the conversion coefficient output by the entropy decoding unit. An inverse quantization / inverse conversion unit that performs inverse conversion processing to restore the predicted residual in block units, a synthesis unit that synthesizes the predicted block and the restored predicted residual, and restores the decoding target block. The entropy decoding unit is applied to binarization of the final significance coefficient coordinates indicating the position of the final significance coefficient included in the conversion coefficient based on the intra prediction mode used for the intra prediction. The gist is to have a decoding control unit that specifies the method.

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 that improve the efficiency of coding the last position.

It is a figure which shows the structure of the coding apparatus 1 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 structure of the entropy coding part which concerns on embodiment. It is a figure which shows the operation example of the serialization part which concerns on embodiment. It is a figure which shows the operation example of the serialization part which concerns on embodiment. It is a figure which shows the operation of the coding control unit and the decoding control unit which concerns on embodiment. It is a figure which shows the association information which concerns on embodiment. It is a figure which shows the number of bits required for the representation of a coordinate value. It is a figure which shows the structure of the decoding apparatus which concerns on embodiment. It is a figure which shows the structure of the entropy decoding part which concerns on embodiment. It is a figure for demonstrating another 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.

<Coding device>
The coding apparatus according to this embodiment will be described.

(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 synthesizes a block dividing unit 100, a subtracting unit 110, a conversion / quantization unit 120, an entropy coding unit 130, an inverse quantization / inverse conversion unit 140, and the like. It has a 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 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.

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.

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.

Intra-prediction mode syntax 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".

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.

FIG. 2 is a diagram showing candidates for the intra prediction mode according to the present embodiment. As shown in FIG. 2, there are 67 candidates for the intra prediction mode 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 modes "2" to "18" are prediction modes that refer to reference pixels only on the left side of the target block for intra prediction. On the other hand, the modes "50" to "66" are prediction modes that refer to reference pixels only on the upper side of the target block for intra prediction.

As described above, the coding device 1 according to the present embodiment encodes in block units constituting the image. The coding device 1 has an intra prediction unit 172 that generates a prediction block corresponding to the coding target block by intra prediction using decoded pixels around the coding target block, and a difference between the coding target block and the prediction block. The conversion / quantization unit 120 that performs conversion processing and quantization processing on the predicted residual of the block unit representing the above, and the entropy coding unit 130 that encodes the conversion coefficient of the block unit output by the conversion / quantization unit 120. And have.

(Structure of entropy encoding unit)
Next, the configuration of the entropy encoding unit 130 according to the present embodiment will be described. FIG. 3 is a diagram showing the configuration of the entropy coding unit 130 according to the present embodiment.

As shown in FIG. 3, the entropy coding unit 130 includes a serialization unit 131, a binarization unit 132, a coding unit 133, and a coding control unit 134.

The serialization unit 131 scans (serializes) the conversion coefficient in the block with respect to the conversion coefficient in the block unit in the scanning order, and outputs the serialized conversion coefficient to the binarization unit 132.

4 and 5 are diagrams showing an operation example of the serialization unit 131 according to the present embodiment. 4 and 5 show an example in which the size of the coded block is 8 × 8. Here, an example of scanning in units of subblocks in units of 4 × 4 is shown.

As shown in FIG. 4, the serialization unit 131 scans the conversion coefficient in the block from the highest frequency component toward the DC component by oblique scanning.

As shown in FIG. 5, the serialization unit 131 generates the last significance coordinate (last position) indicating the position of the last significance coefficient on the highest frequency side among the serialized conversion coefficients, and binarizes the last position. Output to unit 132. Specifically, the serialization unit 131 represents the last position in which the coordinates of the first significance coefficient in the scan order (that is, the relative position with respect to the DC component) are expressed by two values of x and y (last_sig_coeff_x, last_sig_coeff_y). Output to the binarization unit 132. Here, last_sig_coeff_x is the X coordinate value, and last_sig_coeff_y is the Y coordinate value. In the example of FIG. 5, (last_sig_coeff_x, last_sig_coeff_y) = (6, 5). Each of last_sig_coeff_x and last_sig_coeff_y is composed of a prefix portion and a suffix portion.

Further, the serialization unit 131 generates various information (syntax elements) indicating the configuration of the conversion coefficient in sub-block units, and outputs the generated information to the binarization unit 132. For example, the serialization unit 131 outputs coded_sub_block_flag, which is a flag indicating whether or not there is a significance coefficient in the subblock, to the binarization unit 132. In the example of FIG. 5, the serialization unit 131 outputs a coded_sub_block_flag indicating that there is no significance coefficient in the lower left subblock to the binarization unit 132.

Further, in the present embodiment, the coding control unit 134 is applied to the binarization of the last position indicating the position of the final significance coefficient included in the conversion coefficient based on the intra prediction mode syntax output by the intra prediction unit 172. Determine the binarization method to be performed. The coding control unit 134 controls the binarization unit 132 so as to perform binarization by the determined binarization method.

FIG. 6 is a diagram showing the operation of the coding control unit 134 according to the present embodiment.

As shown in FIG. 6A, when the intra prediction mode applied to the coded block indicates the vertical direction prediction mode, it is highly possible that there is a large conversion coefficient and a final significance coefficient at the upper part of the block. The direction prediction mode in the substantially vertical direction refers to a direction prediction mode within a certain range including the vertical direction prediction among the direction prediction modes shown in FIG.

Further, among the direction prediction modes shown in FIG. 2, the direction prediction mode within a certain range including the horizontal direction prediction is referred to as a substantially horizontal direction direction prediction mode.

In the present embodiment, the coding control unit 134 is in a substantially vertical directional prediction mode or is substantially horizontal, depending on the intra prediction mode syntax indicating the intra prediction mode used for the intra prediction of the coded block. Determines whether it is a directional prediction mode or another prediction mode. Here, the coding control unit 134 does not specify the intra prediction mode from the intra prediction mode syntax indicating the intra prediction mode, but in the direction prediction mode in the substantially vertical direction from the intra prediction mode syntax indicating the intra prediction mode. It directly determines whether there is a directional prediction mode in a substantially horizontal direction, or a prediction mode other than that.

Specifically, the coding control unit 134 indicates the 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”. From the intra prediction mode syntax, it is directly determined whether the prediction mode is the direction prediction mode in the substantially vertical direction, the direction prediction mode in the substantially horizontal direction, or the other prediction mode.

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 coding control unit 134 uses the association information that associates each non-MPM mode number with the group of the intra prediction mode. , Depending on the non-MPM mode number (intra_luma_mpm_reminder) included in the intra prediction mode syntax indicating the intra prediction mode, whether it is a substantially vertical direction prediction mode or a substantially horizontal direction prediction mode. Determine if the prediction mode is other than.

FIG. 7 is a diagram showing association information according to the present embodiment.

As shown in FIG. 7, 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. Each non-MPM mode number is associated with a group of intra-prediction modes.

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. 7, 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 substantially horizontal direction prediction mode (group = 1), the second group is associated with the substantially vertical direction prediction mode (group = 2), and the third group. Is associated with other prediction modes (group = 0).

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 group = 1 or group = 2. Further, this range is not fixed to the example shown in FIG. 7, and the range is variable.

Further, when intra_luma_mpm_flag is "1" and intra_luma_mpm_flag is "0" (that is, when intra_luma_mpm_flag indicates that the intra prediction mode used for intra prediction is included in MPM mode), group = 0 (that is). Prediction mode other than) is determined.

When intra_luma_mpm_flag indicates that the intra prediction mode is included in the non-MPM mode, the coding control unit 134 uses the table (correspondence information) as shown in FIG. 7 to use the non-MPM included in the intra prediction mode syntax. Since the mode number (intra_luma_mpm_reminder) can be converted into a scan order number (either "0", "1", or "2"), the non-MPM mode number can be converted into a direction prediction mode in a substantially horizontal direction or a direction prediction mode in a substantially horizontal direction. It is possible to directly determine whether it is the direction prediction mode of the direction or the other prediction mode.

As shown in FIG. 6A, when the intra prediction mode syntax applied to the coded block indicates a direction prediction mode in a substantially vertical direction, the coding control unit 134 sets the X coordinate constituting the last position. The fixed-length binarization method is applied to the value (last_sig_coeff_x), and the variable-length binarization method is applied to the Y coordinate value (last_sig_coeff_y) constituting the last position.

Here, the fixed-length binarization method is a binarization method in which the number of bits after binarization becomes the default number of bits. The fixed-length binarization method may be referred to as fixed-length binarization. In the following, the coordinate value to which the fixed length binarization method should be applied is appropriately referred to as "P coordinate value".

On the other hand, the variable length binarization method is a binarization method in which the number of bits after binarization increases as the coordinate value increases. In other words, the variable length binarization method is a binarization method in which the number of bits after binarization decreases as the coordinate value decreases. The variable length binarization method may be tranked rice binarization. In the following, the coordinate value to which the variable length binarization method should be applied is appropriately referred to as "Q coordinate value".

When the coordinate value is small, the variable length binarization method has a smaller number of bits after binarization than the fixed length binarization method. In the case of FIG. 6A, there is a high possibility that the final significance coefficient is at the upper part of the block, that is, there is a high possibility that the Y coordinate value is a small value. By applying, the number of bits after binarization can be reduced.

On the other hand, when the coordinate value is large, the fixed-length binarization method has a smaller number of bits after binarization than the variable-length binarization method. In the case of FIG. 6A, there is a high possibility that the final significance coefficient is at the upper part of the block, but the X coordinate value can be a large value. Therefore, by applying the fixed-length binarization method to the X coordinate value (last_sig_coeff_x), the number of bits after binarization can be reduced. However, when the block size is small, the coordinate value is small in the first place, and therefore, as an exception, the variable length binarization method may be applied to the X coordinate value.

As shown in FIG. 6B, when the intra prediction mode applied to the coded block indicates a substantially horizontal directional prediction mode, there may be a large conversion coefficient and a final significance coefficient on the left side of the block. high. As described above, the substantially horizontal directional prediction mode refers to the directional prediction mode within a certain range including the horizontal direction prediction among the directional prediction modes shown in FIG.

Further, as shown in FIG. 6B, when the intra prediction mode applied to the coded target block indicates the directional prediction mode in the substantially horizontal direction, the coding control unit 134 has the X coordinates constituting the last position. The variable length binarization method is applied to the value (last_sig_coeff_x), and the fixed length binarization method is applied to the Y coordinate value (last_sig_coeff_y) constituting the last position.

As described above, when the coordinate value is small, the variable length binarization method has a smaller number of bits after binarization than the fixed length binarization method. In the case of FIG. 6B, there is a high possibility that the final significance coefficient is on the left side of the block, that is, there is a high possibility that the X coordinate value is a small value, so that the X coordinate value (last_sig_coeff_x) is binarized to a variable length. By applying the method, the number of bits after binarization can be reduced.

On the other hand, when the coordinate value is large, the fixed-length binarization method has a smaller number of bits after binarization than the variable-length binarization method. In the case of FIG. 6B, there is a high possibility that the final significance coefficient is on the left side of the block, but the Y coordinate value can be a large value. Therefore, by applying the fixed-length binarization method to the Y coordinate value (last_sig_coeff_y), the number of bits after binarization can be reduced. However, when the block size is small, the coordinate value is small in the first place, so that the variable length binarization method may be applied to the Y coordinate value as an exception.

As shown in FIG. 6C, the intra prediction mode syntax applied to the coded block is an intra prediction mode syntax other than the substantially vertical direction prediction mode and the substantially horizontal direction direction prediction mode. In the case (that is, when the coding control unit 134 determines group = 0), it is likely that there is a large conversion coefficient and final significant coefficient in the upper left part of the block.

In the case of FIG. 7C, the coding control unit 134 applies the variable length binarization method to both the X coordinate value (last_sig_coeff_x) and the Y coordinate value (last_sig_coeff_y) constituting the last position.

As described above, when the coordinate value is small, the variable length binarization method has a smaller number of bits after binarization than the fixed length binarization method. In the case of FIG. 7C, since both the X coordinate value and the Y coordinate value are likely to be small values, the variable length binarization method is used for both the X coordinate value (last_sig_coeff_x) and the Y coordinate value (last_sig_coeff_y). By applying, the number of bits after binarization can be reduced.

Returning to FIG. 3, the binarization unit 132 converts the multi-valued signal output by the serialization unit 131 into a binary signal, and outputs the binary signal to the coding unit 133. The binarization unit 132 binarizes each of last_sig_coeff_x and last_sig_coeff_y according to the binarization method determined by the coding control unit 134.

The coding unit 133 encodes the binary signal output by the binarizing unit 132 by arithmetic coding to generate a coded stream, and outputs the generated coded stream.

(Specific example of binarization)
Next, a specific example of binarization according to the present embodiment will be described.

First, as a comparative example of the present embodiment, a binarization method of the final significance coefficient in the HEVC method will be described. In the HEVC method, the X-coordinate value and the Y-coordinate value of the last significant coefficient in the block are transmitted. The X coordinate value is transmitted separately to the prefix part last_sig_coeff_x_prefix and the suffix part last_sig_coeff_x_suffix.

Here, the minimum value of last_sig_coeff_x_prefix is 0, the maximum value is (log2TrafoSize << 1) -1, and it is binarized by TR (Truncated Rice) (RiceParam = 0). Here, "log2TrafoSize" is a logarithm with the side length of the block being 2 as the base. For example, when the width of the block size is 16, the log2TrafoSize is 4, and the maximum value of the last_sig_coeff_x_prefix to be transmitted is 7.

Here, in the TR of SpeceParam = 0, "1" is arranged by the number of values to be binarized, and if the value is less than the maximum value, "0" is arranged by N at the end to perform binarization. For example, when the maximum value is 7, when 4 is binarized by TR (RiceParam = 0), it becomes "11110", and when 7 is binarized, it becomes "1111111".

The last_sig_coeff_x_suffix is not transmitted when last_sig_coeff_x_prefix <= 3. In the case of last_sig_coeff_x_prefix> 3, the minimum value of the transmitted last_sig_coeff_x_suffix is 0, the maximum value is (1 << ((last_sig_coeff_x_prefix >> 1) -1)) -1, and FL (Fixed-Leng) To. For example, when the block size is 16 × 16 and the last_sig_coeff_x_prefix is 10, the maximum value of the last_sig_coeff_x_sufix to be transmitted is 3.

Here, FL binarizes the value to be binarized as the binary number of the ceil (log2 (maximum value to be binarized + 1)) bit. For example, when the maximum value is 7, when 4 is binarized in FL, it becomes "100", and when 7 is binarized, it becomes "111".

X coordinate values, if Last_sig_coeff_x_suffix is not transmitted determined as X = Last_sig_coeff_x_prefix, the X = (1 << if Last_sig_coeff_x_suffix is transmitted ((last_sig_coeff_x_prefix >> 1) -1) * (2+ (last_sig_coeff_x_prefix & 1)) + last_sig_coeff_x_suffix Ask as.

The same applies to the Y coordinate value, and transmission is performed using last_sig_coeff_y_prefix and last_sig_coeff_y_suffix.

In the VVC method, which is the next-generation coding method, since there are rectangular blocks, log2ZoTbWith, which is the logarithm of the block size width with the base of 2, is used for the X coordinate value instead of the above log2TrafoSize. Is different in that log2ZoTbHeight, which is a logarithm with the height of the block size of 2 as the base, is used.

As described above, the number of binarized bits used to represent the X-coordinate value and the Y-coordinate value of the final significance coefficient is the smallest at the upper left of the block and increases toward the right or lower.

FIG. 8 is a diagram showing the number of bits required to represent the coordinate values. Here, an example in the case of a block size of 16 × 16 is shown.

As shown in FIG. 8A, when the X coordinate value of the final significance coefficient is in the region shown by white, only last_sig_coeff_x_prefix is transmitted, and last_sig_coeff_x_sufix is not transmitted. Therefore, it is a region in which the X coordinate value can be expressed by the shortest binarized bit number.

As shown in FIG. 8A, when the X coordinate value of the final significance coefficient is in the area indicated by the diagonal line, last_sig_coeff_x_suffix is transmitted in addition to last_sig_coeff_x_prefix, and the maximum value of last_sig_coeff_x_suffix is 1.

As shown in FIG. 8A, when the X coordinate value of the final significance coefficient is in the shaded area, the last_sig_coeff_x_sufix is also transmitted in addition to the last_sig_coeff_x_prefix, and the maximum value of the last_sig_coeff_x_suffix is 3. Therefore, it is an area where the longest binarized bit number is required to represent the X coordinate value.

The same applies to the Y coordinate value, and each region is shown in FIG. 8 (b).

Since the binarization method of the comparative example does not consider the direction of intra-prediction, the number of bits after binarization can increase. For example, in the case of the direction prediction mode in the substantially vertical direction (that is, the direction prediction mode close to vertical), if the X coordinate value is large even though the probability that the final significance coefficient appears at the upper part of the block is high, X The number of bits required to represent the coordinate values increases.

For example, in the case of the directional prediction mode in the substantially vertical direction (that is, the directional prediction mode close to vertical), at the position of (X, Y) = (14,0) in the 16 × 16 block shown in FIG. The possibility of having a final significance coefficient is higher than the possibility of having a final significance coefficient at the position (X, Y) = (0,3). However, the case where the final significance coefficient is located at the position (X, Y) = (14,0) is higher than the case where the final significance coefficient is located at the position (X, Y) = (0,3). The number of binarized bits required to express the final significance coefficient position increases.

Specifically, when the X coordinate value “14” of (X, Y) = (14,0) is binarized, the last_sig_coeff_x_prefix = “1111111” and the last_sig_coeff_x_sufix = “10”, and the Y coordinate value “0” is obtained. When binarized, last_sig_coeff_y_prefix = "0" and last_sig_coeff_y_suffix are not transmitted, and the total number of bits after binarization is 10 bits in total of the X coordinate value and the Y coordinate value.

On the other hand, when the X coordinate value “0” of (X, Y) = (0,3) is binarized, there is no last_sig_coeff_x_prefix = “0” and last_sig_coeff_x_suffix transmission, and when the Y coordinate value “3” is binarized, Last_sig_coeff_y_prefix = "1110", last_sig_coeff_y_suffix is not transmitted, and the total number of binarized bits of the X coordinate value and the Y coordinate value is 5 bits.

Since the binarization unit 133 performs arithmetic coding on the prefix after this, the number of bits after binarization is not directly linked to the length of the stream after coding, but the number of bits before arithmetic coding is small. Generally, the encoded stream also tends to be short. On the other hand, since the suffix is encoded by bypass, the number of bits after binarization and the number of bits after encoding match.

Secondly, the binarization according to the present embodiment will be described. In the following specific example, the terms P coordinate value and Q coordinate value are used instead of the X coordinate value and the Y coordinate value.

As described above, since the P coordinate value is binarized by the fixed length binarization method, the change in the number of bits after binarization according to the position is small. On the other hand, since the Q coordinate value is binarized by the same variable length binarization method as HEVC, the number of bits after binarization changes greatly depending on the position.

In the following, the length of the side of the block corresponding to the P coordinate value is defined as pSize, and the logarithm with the base 2 of pSize is defined as log2pSize. Let qSize be the length of the side of the block corresponding to the Q coordinate value, and let log2qSize be the logarithm of qSize with 2 as the base.

In the present embodiment, when the intra prediction mode syntax is the directional prediction mode in the substantially vertical direction, the representation of the P coordinate value is used as the representation of the X coordinate value, and the representation of the Q coordinate value is used as the representation of the Y coordinate value. .. When the intra prediction mode syntax is the directional prediction mode in the substantially horizontal direction, the expression of the Q coordinate value is used as the expression of the X coordinate value, and the expression of the P coordinate value is used as the expression of the Y coordinate value. In other cases, the expression of the Q coordinate value is used for both the expression of the X coordinate value and the expression of the Y coordinate value (in this case, both the X coordinate value and the Y coordinate value are equal to the binarization method of HEVC).

The entropy encoding unit 130 transmits the last_sig_coeff_p_sufix for the P coordinate value, and does not transmit the last_sig_coeff_p_prefix. The maximum value of last_sig_coeff_p_sufix is pLength.

The entropy encoding unit 130 transmits both last_sig_coeff_q_prefix and last_sig_coeff_q_sufix for the Q coordinate value. The minimum value of last_sig_coeff_q_prefix is 0, and the maximum value is (log2qSize << 1) -1. Here, log2qSize is a logarithm with the side length of the block being 2 as the base. For example, when the width of the conversion block size is 16, log2qSize is 4, and the maximum value of the transmitted last_sig_coeff_q_prefix is 7.

The last_sig_coeff_q_suffix is not transmitted when last_sig_coeff_q_prefix <= 3. In the case of last_sig_coeff_q_prefix> 3, the minimum value of the transmitted last_sig_coeff_q_sufix is 0, and the maximum value is (1 << ((last_sig_coeff_q_prefix >> 1) -1) -1) -1.

Q coordinate values, if Last_sig_coeff_q_suffix is not transmitted determined as Q = Last_sig_coeff_q_prefix, if Last_sig_coeff_q_suffix is transmitted Q = (1 << ((last_sig_coeff_q_prefix >> 1) -1) * (2+ (last_sig_coeff_q_prefix & 1)) + last_sig_coeff_q_suffix Ask as.

In the present embodiment, under the same conditions as above, when each of (X, Y) = (14,0) and (X, Y) = (0,3) is binarized in a 16 × 16 block, It looks like this: Specifically, in the case of the direction prediction mode in the substantially vertical direction, the expression of the P coordinate value is used as the expression of the X coordinate value, and the expression of the Q coordinate value is used as the expression of the Y coordinate value.

When the X coordinate value (P coordinate value) “14” of (X, Y) = (14,0) is binarized, the last_sig_coeff_x_prefix is no transmission, the last_sig_coeff_x_sufix = “1110”, and the Y coordinate value (Q coordinate value). When "0" is binarized, last_sig_coeff_y_prefix = "0" and last_sig_coeff_y_suffix are not transmitted, and the total number of bits after binarization is 5 bits in total of the X coordinate value and the Y coordinate value.

When the X coordinate value (P coordinate value) “0” of (X, Y) = (0,3) is binarized, the last_sig_coeff_x_prefix is not transmitted, the last_sig_coeff_x_sufix = “0000”, and the Y coordinate value (Q coordinate value). When "3" is binarized, last_sig_coeff_y_prefix = "1110" and last_sig_coeff_y_suffix are not transmitted, and the total number of bits after binarization is 8 bits in total of the X coordinate value and the Y coordinate value.

In the case of the direction prediction mode in the substantially vertical direction, the probability that the final significance coefficient is at the position (X, Y) = (14,0) is the final significance coefficient at the position (X, Y) = (0,3). Therefore, according to the entropy coding unit 130 according to the present embodiment, the number of bits after binarization can be reduced as compared with the comparative example.

However, in the present embodiment, when the maximum value of the P coordinate value and the maximum value of the Q coordinate value are significantly different, that is, when the block has a vertically or horizontally long shape, the entropy coding unit 130 also has the P coordinate value. It may be binarized and transmitted in the conventional representation (ie, variable length binarization method). The term "significantly different" means that the maximum value of the larger of the P coordinate value and the Q coordinate value is, for example, twice or more the maximum value of the smaller one.

Further, in the present embodiment, when the maximum value of the P coordinate value is equal to or less than a predetermined value, the entropy coding unit 130 also binarizes the P coordinate value by the conventional expression (that is, the variable length binarization method). It may be transmitted. The predetermined value is, for example, 4.

<Decoding device>
Next, the decoding device according to the present embodiment will be mainly described as being different from the coding device 1 described above.

(Configuration of decoding device)
FIG. 9 is a diagram showing a configuration of a decoding device 2 according to the present embodiment. As shown in FIG. 9, the decoding device 2 includes an entropy decoding unit 200, an inverse quantization / inverse conversion unit 210, a synthesis unit 220, a memory 230, and a prediction unit 240.

The entropy decoding unit 200 decodes the coded stream generated by the coding device 1. The entropy decoding unit 200 acquires information on the prediction process and information on the conversion process, outputs the information on the prediction process to the prediction unit 240, and outputs the information on the conversion process to the inverse quantization / inverse conversion unit 210. Information about the prediction process includes intra-prediction mode syntax.

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 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.

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 decodes each block constituting the image. The decoding device 2 has an intra prediction unit 242 that generates a prediction block corresponding to the decoding target block by intra prediction using the decoded pixels around the decoding target block, and a decoding target block by decoding the coded stream. The entropy decoding unit 200 that outputs the conversion coefficient and the inverse quantization / inverse conversion unit 210 that restores the predicted residual in block units by performing inverse quantization processing and inverse conversion processing on the conversion coefficient output by the entropy decoding unit. And a synthesis unit 220 that restores the decoding target block by synthesizing the predicted block and the restored predicted residual.

(Structure of entropy decoding unit)
Next, the configuration of the entropy decoding unit 200 according to the present embodiment will be described. FIG. 10 is a diagram showing the configuration of the entropy decoding unit 200 according to the present embodiment.

As shown in FIG. 10, the entropy decoding unit 200 includes a decoding unit 201, a multi-valued unit 202, a deserialization unit 203, and a decoding control unit 204.

The decoding unit 201 parses the coded stream and decodes the binary signal from the coded stream. In the present embodiment, the decoding unit 201 acquires the intra prediction mode syntax and outputs the intra prediction mode syntax to the decoding control unit 204.

Under the control of the decoding control unit 204, the multi-value conversion unit 202 converts the binary signal output by the decoding unit 201 into a multi-value signal, and outputs the multi-value signal to the deserialization unit 203. This restores the quantized conversion factor. Further, the multi-valued unit 202 converts the binarized last position (last_sig_coeff_x, last_sig_coeff_y) into a coordinate value which is a multi-valued signal and outputs it.

The deserialization unit 203 outputs the conversion coefficient (quantized conversion coefficient) in block units to the inverse quantization unit 211 by deserializing the multi-valued signal output by the multi-valued unit 202 according to the scanning order. To do.

The decoding control unit 204 identifies the binarization method applied to the binarization of the last position based on the intra-prediction mode syntax indicating the intra-prediction mode applied to the decoding target block. The decoding control unit 204 controls the multi-value unit 202 so as to perform multi-value according to the specified binarization method.

In the present embodiment, the decoding control unit 204 is in a substantially vertical direction prediction mode or a substantially horizontal direction depending on the intra prediction mode syntax indicating the intra prediction mode used for the intra prediction of the block to be decoded. Determine whether it is a sex prediction mode or another prediction mode. Here, the decoding control unit 204 does not specify the intra prediction mode from the intra prediction mode syntax, and is in the direction prediction mode in the substantially vertical direction from the intra prediction mode syntax indicating the intra prediction mode, or in the substantially horizontal direction. It directly determines whether it is the direction prediction mode of or other prediction modes. Such a direct determination operation is the same as the determination operation in the coding control unit 134 described above.

As shown in FIG. 6A, when the intra prediction mode syntax applied to the decoding target block indicates the directionality prediction mode in the substantially vertical direction, the decoding control unit 204 sets the X coordinate value (last_sig_coeff_x) constituting the last position. ), The multi-valued version corresponding to the fixed-length binarization method is applied, and the multi-valued value corresponding to the variable-length binarization method is applied to the Y coordinate value (last_sig_coeff_y) constituting the last position.

As shown in FIG. 7B, when the intra prediction mode syntax applied to the decoding target block indicates the directionality prediction mode in the substantially horizontal direction, the decoding control unit 204 sets the X coordinate value (last_sig_coeff_x) constituting the last position. ), The multi-valued version corresponding to the variable-length binarization method is applied, and the multi-valued value corresponding to the fixed-length binarization method is applied to the Y coordinate value (last_sig_coeff_y) constituting the last position.

As shown in FIG. 7C, when the intra-prediction mode syntax applied to the decoding target block is an intra-prediction mode syntax other than the substantially vertical direction prediction mode and the substantially horizontal direction direction prediction mode. The decoding control unit 204 applies multi-valued corresponding to the variable length binarization method to both the X coordinate value (last_sig_coeff_x) and the Y coordinate value (last_sig_coeff_y) constituting the last position.

<Action / effect>
The entropy coding unit 130 according to the present embodiment is binarized to be applied to the binarization of the last position indicating the position of the final significance coefficient included in the conversion coefficient based on the intra prediction mode syntax used for the intra prediction. It has a coding control unit 134 that determines the method.

Further, the entropy decoding unit 200 according to the present embodiment is applied to binarize the last position indicating the position of the final significance coefficient included in the conversion coefficient based on the intra prediction mode syntax used for the intra prediction. It has a decoding control unit 204 that specifies a binarization method.

In this way, by controlling the binarization for transmitting the last position according to the intra-prediction mode syntax, the efficiency of coding the last position can be improved.

<Change example>
In the above-described embodiment, an example has been described in which the coding control unit 134 directly determines the binarization method from this syntax without specifying the intra prediction mode from the syntax indicating the intra prediction mode. Similarly, an example in which the decoding control unit 204 directly specifies the binarization method from this syntax without specifying the intra prediction mode from the syntax indicating the intra prediction mode has been described.

However, as a modification of the embodiment, the coding control unit 134 may specify the intra prediction mode from the syntax indicating the intra prediction mode, and then determine the binarization method from the specified intra prediction mode. Similarly, as a modification of the embodiment, the decoding control unit 204 may specify the intra prediction mode from the syntax indicating the intra prediction mode, and then specify the binarization method from the specified intra prediction mode.

Therefore, "determining / specifying the binarization method based on the intra-prediction mode" means that the binarization method is determined / specified by the method of the above-described embodiment and the method of the modification of the embodiment. It shall include both cases of determining and specifying the binarization method.

<Other Embodiments>
As mentioned above, in the near-vertical intra-prediction, it is highly likely that a large conversion coefficient appears at the top of the block. However, as shown in FIG. 11, it is considered that the position with a high probability of appearing changes to the left side of the block as the distance from the upper part of the block is increased. The black-painted area shown in FIG. 11 is an area in which it is highly likely that a conversion coefficient of a large value appears when an intra-prediction that is close to vertical is performed. In such a case, it is considered that the efficiency can be improved by changing the expression of the P coordinate value according to the Q coordinate value.

Therefore, the entropy coding unit 130 transmits the Q coordinate value in the same manner as in the above-described embodiment. On the other hand, with respect to the P coordinate value, the entropy coding unit 130 changes the maximum value of last_coeff_p_sufix used for expressing the P coordinate value according to the Q coordinate value. Specifically, the entropy encoding unit 130 does not transmit last_coeff_p_sufix when the maximum value of last_coeff_p_sufix is 0. For example, when the Q coordinate value is N or less, the entropy coding unit 130 sets the maximum value of last_coeff_p_sufix to 0 when transmitting the P coordinate value, and does not transmit the last_coeff_p_sufix. When the Q coordinate value is larger than N, the P coordinate value is transmitted in the same expression as before. N is preferably a small value such as 0 or 1. In this way, the entropy coding unit 130 (coding control unit 134) applies the variable length binarization method to the P coordinate value instead of the fixed length binarization method based on the Q coordinate value.

When the binarization method of the P coordinate value is changed according to the Q coordinate value, the entropy coding unit 130 transmits the Q coordinate value before the transmission of the P coordinate value. For example, when the intra prediction mode applied to the coded block is the directionality prediction mode in the substantially vertical direction, the entropy coding unit 130 sets X coordinate value = P coordinate value and Y coordinate value = Q coordinate value, and Y The coordinate value is transmitted first, and the X coordinate value is transmitted later. In other cases, the X coordinate value is transmitted first and the Y coordinate value is transmitted later as in the conventional case.

A program that causes the 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: Serialization unit 132: Binarization unit 133: Coding unit 134: Coding 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: Decoding unit 202: Multi-valued unit 203: Deserialization unit 204: Decoding 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

Claims (10)

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 predicted residual in block units representing the difference between the coded block and the predicted block.
It is provided with an entropy coding unit that encodes the conversion coefficient of each block output by the conversion / quantization unit.
The entropy encoding unit determines a binarization method applied to binarization of the final significance coefficient coordinates indicating the position of the final significance coefficient included in the conversion coefficient based on the intra prediction mode used for the intra prediction. A coding device having a coding control unit for the function of the code. When the coding control unit determines the binarization method based on the syntax indicating the intra prediction mode, the binarization method is performed from the syntax without specifying the intra prediction mode from the syntax. The coding apparatus according to claim 1, wherein the coding apparatus is directly determined. Based on the intra prediction mode, the coding control unit applies a fixed-length binarization method to one coordinate value that constitutes the final significance coefficient coordinate, and the other coordinate that constitutes the final significance coefficient coordinate. Apply the variable length binarization method to the value,
The fixed-length binarization method is a binarization method in which the number of bits after binarization becomes the default number of bits.
The coding apparatus according to claim 1 or 2, wherein the variable length binarization method is a binarization method in which the number of bits after binarization increases as the other coordinate value increases. When the intra prediction mode is a directional prediction mode in a substantially vertical direction, the coding control unit applies the fixed length binarization method to the X coordinate value as the one coordinate value, and the other coordinate. Applying the variable length binarization method to the Y coordinate value as the value,
When the intra prediction mode is a directional prediction mode in a substantially horizontal direction, the coding control unit applies the fixed length binarization method to the Y coordinate value as the one coordinate value, and the other coordinate. The coding apparatus according to claim 3, wherein the variable length binarization method is applied to an X coordinate value as a value. The coding control unit is characterized in that the variable length binarization method is applied to the one coordinate value instead of the fixed length binarization method based on the size or shape of the coded block. The coding apparatus according to claim 4. 4. The coding control unit is characterized in that the variable length binarization method is applied to the one coordinate value instead of the fixed length binarization method based on the other coordinate value. Or the coding apparatus according to 5. When the binarization method of the one coordinate value is different based on the other coordinate value, the entropy encoding unit transmits the other coordinate value before the transmission of the one coordinate value. The coding apparatus according to claim 6, wherein the coding apparatus is characterized by the above. A decoding device that decodes each block that constitutes an image.
An intra prediction unit that generates a prediction block corresponding to the decoding target block by intra prediction using decoded pixels around the decoding target block, and an intra prediction unit.
An entropy decoding unit that outputs the conversion coefficient of the block to be decoded by decoding the coded stream, and
An inverse quantization / inverse transformation unit that restores the predicted residuals in block units 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 predicted block and the restored predicted residual to restore the decoding target block is provided.
The entropy decoding unit identifies a binarization method applied to binarization of the final significance coefficient coordinates indicating the position of the final significance coefficient included in the conversion coefficient based on the intra prediction mode used for the intra prediction. A decoding device characterized by having a decoding control unit. The entropy decoding unit acquires a syntax indicating the intra prediction mode used for the intra prediction, and obtains a syntax indicating the intra prediction mode.
The decoding device according to claim 8, wherein the decoding control unit directly identifies the binarization method from the syntax without specifying the intra prediction mode from the syntax. A program comprising the computer functioning as the coding device according to any one of claims 1 to 7 or the decoding device according to claim 8 or 9.

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