JP2021090219A - Encoder, decoder and program - Google Patents

Abstract

To improve coding performance by reducing entropy efficiently, in intra-prediction.SOLUTION: An encoder 1 includes an intra-prediction unit 14a for generating a prediction image by using intra-prediction mode, a residual signal generation unit 14b for generating a residual signal by the difference of a prediction image and an original image, an orthogonal transformation unit 14c1 performing orthogonal transformation processing after inverting the residual signal to at least one of horizontal direction and vertical direction, when at least one of the right side and underside is included in the position of a reference pixel used for generation of the prediction image, and a secondary orthogonal transformation unit 14c2 for selecting secondary orthogonal transformation processing to be applied among a prescribed secondary orthogonal transformation group, according to the intra-prediction mode and the position of a reference pixel, and applying the selected secondary orthogonal transformation processing to a signal outputted from the orthogonal transformation unit 14c1.SELECTED DRAWING: Figure 2

Description

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

In the moving image (video) coding method represented by H.265 / HEVC (High Efficiency Video Coding), there are two types of inter-prediction using temporal correlation between frames and intra-prediction using spatial correlation within frames. It is configured to output a stream obtained by performing orthogonal conversion processing, loop filtering processing, and entropy coding processing after performing prediction while switching between types of prediction to generate a residual signal.

In intra-prediction in HEVC, a total of 35 types of intra-prediction modes such as Planar prediction, DC prediction, and direction prediction are prepared, and intra-prediction is performed using adjacent decoded reference pixels according to the intra-prediction mode determined by the encoder. It is configured to do. Hereinafter, unless otherwise specified, the description "reference pixel" shall indicate a decoded reference pixel.

Here, in the intra prediction in HEVC, in the CU in which there is no adjacent reference pixel such as the coded target block (hereinafter referred to as “CU: Coding Unit”) located at the upper left in the frame, the specified value (10). If it is a moving image of a bit, it is configured to create a reference pixel to be used when generating a predicted image by a process of filling "512").

Further, in the conventional HEVC, since the coding process is performed in the raster scan order from the upper left, the reference pixel may not be decoded. In such a case, the predicted image is generated by using the value obtained by extrapolating the nearest decoded reference pixel to the 0th order.

In particular, in the conventional intra-prediction in HEVC, the reference pixels located on the lower left side and the upper right side of the CU are often not decoded due to the coding process in the raster scan order. In such a case, the reference pixels that have not been decoded are not decoded. There is a problem that the prediction accuracy is lowered and the coding efficiency is lowered when the direction is predicted from the direction in which the is present.

In order to solve this problem, in intra-prediction, the raster scan order (for example, Z type) is used as the coding processing order for a plurality of conversion blocks (hereinafter, referred to as “TU: Patent Unit”) existing in the CU. In addition, there is known a technique for improving prediction accuracy by giving a degree of freedom in the coding order of U-type, X-type, etc. (see Non-Patent Document 1).

Further, the intra prediction used in HEVC is a prediction using spatially adjacent upper or left reference pixels, and the prediction pixel at a position close to the reference pixel has high accuracy, and the prediction at a position far from the reference pixel is performed. Pixel accuracy tends to be low (see FIG. 10).

In addition, in the figure of this specification, the arrow indicating the direction (prediction direction) of the intra prediction mode is assumed to go from the pixel to be the target of the intra prediction to the reference pixel as described in the HEVC standard (the same applies hereinafter). ..

In conventional HEVC, by utilizing such a property, discrete sine transform (DST: Discrete Cosine Transform) or discrete cosine transform (DCT: Discrete Cosine Transform) or the like is performed in the horizontal and vertical directions from the left and upper directions where the reference pixel is located. The orthogonal transform process of is applied to reduce the entropy of the residual signal.

In particular, as shown in FIG. 11, the shape of the impulse response of the DST is an asymmetrical shape in which one of the end points is closed and the other end point is widened. Therefore, as shown in FIG. By applying DST according to the signal strength of the residual signal, the entropy can be effectively reduced.

By the way, in Non-Patent Document 2, in the orthogonal transformation process (DCT or DST) applied in the conventional HEVC, a secondary orthogonal transform process (hereinafter, quadratic orthogonal matrix) is applied to a residual signal whose entropy is difficult to reduce. A technique for efficiently reducing entropy by applying conversion processing) is disclosed.

Specifically, in the technique described in Non-Patent Document 2, after applying the conventional orthogonal transformation processing to the residual signal obtained by the intra prediction, the obtained orthogonal transformation coefficient is reduced to a small block. It is configured to be divided and a quadratic orthogonal transformation process is applied to each block.

Here, the encoding device selects the optimum quadratic orthogonal transformation process from the quadratic orthogonal transform process group (set of quadratic orthogonal transform processes) in which a plurality of types of bases are prepared, and selects the second orthogonal transform process. Output the flag information indicating the next orthogonal transformation process as a stream (output the flag information indicating that the secondary orthogonal transformation process is not applied when it is optimal not to apply the secondary orthogonal transform process). It is configured.

Further, in the technique described in Non-Patent Document 2, since the characteristics of the residual signal and the characteristics of the orthogonal transformation coefficient differ depending on the direction of the intra prediction mode, the quadratic orthogonal transformation that can be selected according to the intra prediction mode It is configured to switch processing groups.

As a result, the optimum quadratic orthogonal transformation processing can be selected from the quadratic orthogonal transformation processing group specified for each intra prediction mode, and the amount of information required for the flag indicating which quadratic orthogonal transformation processing is used. It is possible to reduce.

Mochizuki et al., "Applied intra-prediction method based on average value coordinates", IPSJ Research Report, vol, 2012-AVM-77, No.12 X.Zhao, J.Chen, M.Karkzewicz, "Mode-dependent non-separable secarable transition", ITU-T SG16 / Q6 Doc. COM16-C1044, October 2015

However, in the technique described in Non-Patent Document 2, the optimum quadratic from the quadratic orthogonal transformation processing group is selected according to the intra prediction mode without considering the position of the reference pixel used in the intra prediction mode. It is configured to determine the orthogonal transformation process.

Here, the characteristics of the residual signal obtained by the intra prediction using the reference pixels on the right side and the lower side are different from the characteristics of the residual signal obtained by the intra prediction using the reference signals on the upper side and the left side.

Therefore, in the technique described in Non-Patent Document 2, when intra-prediction is performed using the reference pixels on the right side or the lower side, if the quadratic orthogonal transformation processing group is switched only in the intra-prediction mode, instead. There is a problem that the entropy may increase and the coding performance may decrease.

Therefore, the present invention has been made to solve the above-mentioned problems, and provides a coding device, a decoding device, and a program capable of efficiently reducing entropy and improving coding performance in intra-prediction. The purpose is to provide.

The first feature of the present invention is a coding device configured to divide the original image of each frame constituting the moving image into coding target blocks and encode the original image, using the intra-prediction mode. An intra prediction unit configured to generate a prediction image, and a residual signal configured to generate a residual signal based on the difference between the prediction image generated by the intra prediction unit and the original image. When at least one of the right side and the lower side is included in the position of the generation unit and the reference pixel used for generating the predicted image, the residual signal generated by the residual signal generation unit is at least horizontal and vertical. Among the orthogonal transforming units configured to perform orthogonal transform processing after being inverted to one side, and the quadratic orthogonal transform group defined in advance according to the intra prediction mode and the position of the reference pixel. It is provided with a quadratic orthogonal transform unit configured to select the quadratic orthogonal transform process to be applied from the above and to perform the selected quadratic orthogonal transform process on the signal output from the orthogonal transform unit. The gist is that.

The second feature of the present invention is a decoding device configured to divide the original image of each frame constituting the moving image into coding target blocks and decode it, and the prediction image using the intra prediction mode. The intra-prediction unit configured to generate the above, the inverse quantization unit configured to perform the inverse quantization process on the quantized conversion coefficient, the intra-prediction mode and the prediction image. The quadratic inverse orthogonal transform process to be applied is selected from the predetermined quadratic inverse orthogonal transform group according to the position of the reference pixel used for the generation of the signal, and the signal output from the inverse quantization unit is selected. On the other hand, when the quadratic inverse orthogonal transform unit configured to perform the selected quadratic inverse orthogonal transform process and the position of the reference pixel include at least one of the right side and the lower side, the quadratic It is a gist to include an inverse orthogonal transform unit configured to perform an inverse orthogonal transform process after inverting a signal output from the inverse orthogonal transform unit in at least one of a horizontal direction and a vertical direction.

The third feature of the present invention is a coding device configured to divide the original image of each frame constituting the moving image into coding target blocks and encode the original image, using the intra-prediction mode. An intra prediction unit configured to generate a prediction image, and a residual signal configured to generate a residual signal based on the difference between the prediction image generated by the intra prediction unit and the original image. When at least one of the right side and the lower side is included in the position of the generation unit and the reference pixel used to generate the predicted image, the residual signal generated by the residual signal generation unit is orthogonal and orthogonal to the residual signal. An orthogonal transform unit configured to perform orthogonal transform processing after inverting at least one base in the direction, and a pre-defined secondary degree according to the intra prediction mode and the position of the reference pixel. The quadratic orthogonal transformation process to be applied is selected from the orthogonal transform group, and the selected quadratic orthogonal transform process is applied to the signal output from the orthogonal transform unit. The gist is to have a department.

The fourth feature of the present invention is a decoding device configured to divide the original image of each frame constituting the moving image into coding target blocks and decode it, and the prediction image is predicted by using the intra prediction mode. The intra-prediction unit configured to generate the above, the inverse-quantization unit configured to perform the inverse quantization process on the quantized conversion coefficient, the intra-prediction mode and the prediction image. The quadratic inverse orthogonal transform process to be applied is selected from the predetermined quadratic inverse orthogonal transform group according to the position of the reference pixel used for the generation of the signal, and the signal output from the inverse quantization unit is selected. On the other hand, when the quadratic inverse orthogonal transform unit configured to perform the selected quadratic inverse orthogonal transform process and the position of the reference pixel include at least one of the right side and the lower side, the quadratic Provided with an inverse orthogonal transform unit configured to perform an inverse orthogonal transform process after inverting at least one of the bases in the horizontal direction and the vertical direction with respect to the signal output from the inverse orthogonal transform unit. Is the gist.

A fifth feature of the present invention is a program for making a computer function as a coding device according to the first and third features described above.

A sixth feature of the present invention is a program for making a computer function as a decoding device according to the second and fourth features described above.

According to the present invention, it is possible to provide a coding device, a decoding device and a program capable of efficiently reducing entropy and improving coding performance in intra-prediction.

FIG. 1 is a diagram showing an example of a functional block of the coding device 1 according to the first embodiment. FIG. 2 is a diagram showing an example of a functional block of the orthogonal transformation / quantization unit 14c of the coding apparatus 1 according to the first embodiment. FIG. 3 is a diagram showing an example of the direction of the intra prediction mode used in the first embodiment. FIG. 4 is a diagram showing an example of a method for generating a predicted image according to the first embodiment. FIG. 5 is a diagram showing an example of a method for generating a predicted image according to the first embodiment. FIG. 6 is a flowchart showing an example of the operation of the coding device 1 according to the first embodiment. FIG. 7 is a diagram showing an example of a functional block of the decoding device 3 according to the first embodiment. FIG. 8 is a diagram showing an example of a functional block of the inverse quantization / inverse transformation unit 33b of the decoding apparatus 3 according to the first embodiment. FIG. 9 is a flowchart showing an example of the operation of the decoding device 3 according to the first embodiment. FIG. 10 is a diagram for explaining the prior art. FIG. 11 is a diagram for explaining the prior art. FIG. 12 is a diagram for explaining the prior art.

(First Embodiment)
Hereinafter, the coding device 1 and the decoding device 3 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 9.

Here, the coding device 1 and the decoding device 3 according to the present embodiment are configured to correspond to the intra prediction in the moving image coding method such as HEVC. The coding device 1 and the decoding device 3 according to the present embodiment are configured to be compatible with any moving image coding method as long as it is a moving image coding method that performs intra-prediction.

The coding device 1 according to the present embodiment is configured to divide the original image of each frame constituting the moving image into CUs and encode the original image. Further, the coding device 1 according to the present embodiment may be configured so that the CU can be divided into a plurality of TUs. Hereinafter, in the present embodiment, a case where the CU is divided into a plurality of TUs will be described as an example. However, in the present invention, the CU is not divided into a plurality of TUs, and the position of the reference pixel of the CU is determined. It is also applicable to cases including the lower side and the right side.

In the present embodiment, the specified value (“512” in the case of a 10-bit moving image) is used for the CU to be encoded in which the adjacent decoded reference pixel does not exist, such as the CU located at the upper left in the frame. Since it is configured to create reference pixels to be used when generating a predicted image by the process of filling in, it is possible that all the pixels adjacent to the left side of the CU to be encoded can be used as reference pixels.

As shown in FIG. 1, the coding apparatus 1 according to the present embodiment includes an intra prediction mode determination unit 11, a TU division determination unit 12, a coding order control unit 13, and a sequential local decoding image generation unit 14. It includes a memory 15 and an entropy coding unit 16.

The intra prediction mode determination unit 11 is configured to determine the optimum intra prediction mode to be applied to the CU.

The TU division determination unit 12 is configured to determine whether or not to divide the CU into a plurality of TUs. In the present embodiment, as a method of dividing the CU into a plurality of TUs, a case of four divisions is described as an example, but the number of divisions and the division shape when the CU is divided into a plurality of TUs are described. , Not limited to such cases.

The coding order control unit 13 is configured to determine the coding order of the TUs in the CU based on the intra prediction mode (for example, the direction of the intra prediction mode).

For example, in the coding order control unit 13, when the TU division determination unit 12 determines that the CU is divided into a plurality of TUs, the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is from the lower left. When the direction is toward the upper right (that is, when the direction is predicted from the lower left to the upper right), the coding order of the TUs in the CU is not the conventional raster scan order but the lower left TU in the CU → The coding order is TU at the lower right in the CU → TU at the upper left in the CU → TU at the upper right in the CU, or TU at the lower left in the CU → TU at the upper left in the CU → TU at the lower right in the CU → Of the coding order of TU on the upper right in the CU, a predetermined coding order may be adopted.

The sequential locally decoded image generation unit 14 is configured to generate a locally decoded image (decoded image for each TU) based on the coding order determined by the coding order control unit 13 and the method of dividing the CU into TUs. ing.

Specifically, the sequential local decoding image generation unit 14 follows the coding order determined by the coding order control unit 13 when the TU division determination unit 12 determines that the CU is divided into a plurality of TUs. , Sequentially configured to generate locally decoded images.

As shown in FIG. 1, the sequential local decoding image generation unit 14 includes an intra prediction unit 14a, a residual signal generation unit 14b, an orthogonal transformation / quantization unit 14c, and an inverse quantization unit / inverse orthogonal conversion unit 14d. , A locally decoded image generation unit 14e.

The intra prediction unit 14a is configured to generate a prediction image using the intra prediction mode determined by the intra prediction mode determination unit 11. That is, the intra prediction unit 14a is configured to determine the position of the reference pixel used when generating the prediction image according to the intra prediction mode, and generate the prediction image using the reference pixel.

Further, the intra prediction unit 14a may be configured to generate a prediction image in the coding order determined by the coding order control unit 13.

The residual signal generation unit 14b is configured to generate a residual signal based on the difference between the predicted image generated by the intra prediction unit 14a and the original image.

The orthogonal transformation / quantization unit 14c is configured to perform orthogonal conversion processing and quantization processing on the residual signal generated by the residual signal generation unit 14b to generate a quantized conversion coefficient. ..

As shown in FIG. 2, the orthogonal transform / quantization unit 14c includes an orthogonal transform unit 14c1, a quadratic orthogonal transform unit 14c2, and a quantization unit 14c3.

The orthogonal transform unit 14c1 is configured to perform orthogonal transform processing on the residual signal generated by the residual signal generation unit 14b.

Specifically, the orthogonal transform unit 14c1 predicts when the position of the reference pixel used for generating the predicted image includes at least one of the right side and the lower side (using the reference pixel adjacent to at least one of the right side and the lower side). (When an image is generated), the orthogonal transformation coefficient is obtained by inverting the residual signal generated by the residual signal generation unit 14b in at least one of the horizontal direction and the vertical direction and then performing an orthogonal transformation process. It is configured.

For example, the orthogonal transform unit 14c1 inverts the residual signal in the vertical direction when the position of the reference pixel includes the lower side (when the predicted image is generated by using the reference pixel adjacent to the lower side). It may be configured to perform the orthogonal transformation process.

Alternatively, when the position of the reference pixel includes the right side (when the predicted image is generated using the reference pixel adjacent to the right side), the orthogonal transform unit 14c1 reverses the residual signal in the horizontal direction and then orthogonalizes the signal. It may be configured to perform a conversion process.

The quadratic orthogonal transform unit 14c2 selects the quadratic orthogonal transform process to be applied from the predetermined quadratic orthogonal transform group according to the intra prediction mode and the position of the reference pixel, and from the orthogonal transform unit 14c1. The output signal (orthogonal conversion coefficient) is configured to perform the selected quadratic orthogonal conversion process.

FIG. 3 shows an example of the intra prediction mode used in this embodiment. As shown in FIG. 3, in the present embodiment, the intra prediction modes 2 to 9 are classified into category A, the intra prediction modes 10 to 26 are classified into category B, and the intra prediction modes 27 to 34 are classified into category C. It shall be classified into.

In the present embodiment, an example using the intra prediction mode in HEVC shown in FIG. 3 will be described, but the present invention is also applicable to an example in which another intra prediction mode is used.

Here, the quadratic orthogonal transformation process is a conversion process applied to further reduce the entropy of the orthogonal transform coefficient obtained by applying the orthogonal transform process to the residual signal.

The energy distribution of the residual signal is statistically proportional to the distance from the reference pixel used for the intra prediction. Therefore, the energy distribution of the residual signal is different between the intra prediction mode using only the reference pixels located on the left side and the intra prediction mode using only the reference pixels located on the left side and the upper side. Further, the energy distribution of the orthogonal transformation coefficients obtained by applying the orthogonal transformation processing to these residual signals also differs depending on the intra prediction mode.

Therefore, the technique described in Non-Patent Document 2 utilizes the correlation between the energy bias of the orthogonal transformation coefficient and the direction of the intra prediction mode, and is a quadratic orthogonal matrix that can be selected according to the direction of the intra prediction mode. It is configured to switch the conversion processing group.

In FIGS. 4 (a) and 4 (b), as an example of the energy distribution of the residual signal, the intra prediction mode 2 (intra prediction mode using only the reference pixel located on the left side) and the intra prediction mode 18 (left side) in HEVC are shown. And the difference in the energy distribution of the residual signal in the intra prediction mode) using the reference pixel located on the upper side is shown.

However, as shown in FIG. 5, when the direction prediction of the intra prediction mode 2 is performed using the reference pixels located on the left side and the lower side, the direction prediction of the intra prediction mode 2 is performed using only the reference pixels located on the left side. The energy distribution of the residual signal is also different due to the difference in the position of the reference pixel as compared with the case of performing.

The energy distribution of the residual signal by the direction prediction in the intra prediction mode 2 using the reference pixels located on the left side and the lower side (see FIG. 5) uses the reference pixels located on the left side and the upper side shown in FIG. 4 (b). The energy distribution is the same as that obtained by inverting the residual signal obtained by the direction prediction of the intra prediction mode 18 in the vertical direction.

That is, when the direction prediction in the intra prediction mode 2 is performed, it is obtained when the left side and the lower side are included as the positions of the reference pixels and the orthogonal transformation process is applied after the residual signal is inverted in the vertical direction. The energy distribution of the orthogonal transform coefficient to be obtained is that when the direction prediction of the intra prediction mode 18 is performed, the position of the reference pixel includes the left side and the upper side, and the residual signal is not inverted in the horizontal direction and the vertical direction. The energy distribution of the orthogonal transformation coefficient obtained when the orthogonal transformation processing is applied is the same (see FIGS. 4 (b) and 5).

Since the energy distribution of the orthogonal transformation coefficient obtained by the orthogonal transformation processing for the residual signal by the direction prediction of the intra prediction mode 2 differs depending on the position of the reference pixel used for the intra prediction, it can be applied only based on the intra prediction mode. Determining the next orthogonal transformation processing group may increase the entropy and reduce the coding performance.

Therefore, the quadratic orthogonal transform unit 14c2 is predetermined according to the direction in which the direction of the intra prediction mode is inverted to at least one of the vertical and horizontal directions according to the position of the reference pixel, not the direction of the intra prediction mode. It is configured to use the next orthogonal transformation processing group.

That is, when the intra prediction mode belongs to category B, the quadratic orthogonal transform unit 14c2 applies the quadratic orthogonal transform process to be applied from the quadratic orthogonal transform group defined in advance according to the direction of the intra prediction mode. May be configured to select.

For example, when the intra prediction mode is 18, the quadratic orthogonal transform unit 14c2 selects a quadratic orthogonal transform process to be applied from a predetermined quadratic orthogonal transform group according to the direction of the intra prediction mode 18. It may be configured to do so.

Alternatively, the quadratic orthogonal transform unit 14c2 is predetermined according to the direction of the intra prediction mode when the intra prediction mode belongs to category A and the lower side is not included as the position of the reference pixel. It may be configured to select the quadratic orthogonal transformation process to be applied from the quadratic orthogonal transformation group.

For example, the quadratic orthogonal transform unit 14c2 is predetermined according to the direction of the intra prediction mode 2 when the intra prediction mode is 2 and the lower side is not included as the position of the reference pixel. It may be configured to select the quadratic orthogonal transformation process to be applied from the quadratic orthogonal transformation group.

Alternatively, the quadratic orthogonal transform unit 14c2 is predetermined according to the direction of the intra prediction mode when the intra prediction mode belongs to category C and the right side is not included as the position of the reference pixel. It may be configured to select the quadratic orthogonal transformation process to be applied from the quadratic orthogonal transformation group.

For example, the quadratic orthogonal transform unit 14c2 is predetermined according to the direction of the intra prediction mode 34 when the intra prediction mode is 34 and the right side is not included as the position of the reference pixel. It may be configured to select the quadratic orthogonal transformation process to be applied from the quadratic orthogonal transformation group.

Further, when the position of the reference pixel includes the lower side, the quadratic orthogonal transform unit 14c2 is selected from the quadratic orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is reversed in the vertical direction. It may be configured to select the quadratic orthogonal transformation process to be applied.

Here, "reversing the direction of the intra prediction mode to the vertical direction" means that in the example of FIG. 3, the direction of the intra prediction modes 2 to 9 and the direction of the intra prediction modes 18 to 11 are converted, respectively. That is, it means that the direction of each intra prediction mode is converted to the direction of the intra prediction mode having a line-symmetrical positional relationship with reference to the direction of the intra prediction mode 10.

That is, when the intra-prediction mode belongs to category A and the lower side is included as the position of the reference pixel, the quadratic orthogonal transform unit 14c2 reverses the direction of the intra-prediction mode in the vertical direction. It may be configured to select the quadratic orthogonal transformation process to be applied from the quadratic orthogonal transformation group defined in advance according to the above.

For example, the quadratic orthogonal transform unit 14c2 reverses the direction of the intra prediction mode 2 in the vertical direction (intra) when the intra prediction mode is 2 and the lower side is included as the position of the reference pixel. It may be configured to select the quadratic orthogonal transform process to be applied from the quadratic orthogonal transform group defined in advance according to the direction of the prediction mode 18).

Alternatively, when the position of the reference pixel includes the right side, the quadratic orthogonal transform unit 14c2 is selected from the quadratic orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is reversed in the horizontal direction. It may be configured to select the quadratic orthogonal transformation process to be applied.

Here, "reversing the direction of the intra prediction mode in the horizontal direction" means that in the example of FIG. 3, the direction of the intra prediction mode 18 to 25 and the direction of the intra prediction mode 34 to 27 are converted, respectively. That is, it means that the direction of each intra prediction mode is converted to the direction of the intra prediction mode having a line-symmetrical positional relationship with reference to the direction of the intra prediction mode 26.

That is, when the intra-prediction mode belongs to category C and the right side is included as the position of the reference pixel, the quadratic orthogonal transform unit 14c2 reverses the direction of the intra-prediction mode in the horizontal direction. It may be configured to select the quadratic orthogonal transformation process to be applied from the quadratic orthogonal transformation group defined in advance according to the above.

For example, the quadratic orthogonal transform unit 14c2 reverses the direction of the intra prediction mode 34 in the horizontal direction (intra) when the intra prediction mode is 34 and the right side is included as the position of the reference pixel. It may be configured to select the quadratic orthogonal transform process to be applied from the quadratic orthogonal transform group defined in advance according to the direction of the prediction mode 18).

The quantization unit 14c3 is configured to perform a quantization process on the signal output from the quadratic orthogonal transform unit 14c2 to generate a quantized conversion coefficient.

The inverse quantization unit / inverse orthogonal transform unit 14d again performs inverse quantization processing, quadratic inverse orthogonal transformation, and inverse orthogonal transformation processing on the quantized conversion coefficient generated by the orthogonal transformation / quantization unit 14c. It is configured to be applied to generate a residual signal.

The locally decoded image generation unit 14e generates a locally decoded image by adding the prediction image generated by the intra prediction unit 14a to the residual signal generated by the inverse quantization unit and the inverse orthogonal transform unit 14d. It is configured.

The memory 15 is configured to hold the locally decoded image generated by the sequential locally decoded image generation unit 14 so as to be available as a reference image.

The entropy coding unit 16 is configured to perform entropy coding processing on flag information including an intra prediction mode determined by the intra prediction mode determination unit 11 and a quantized conversion coefficient, and output a stream. There is.

FIG. 6 shows a flowchart for explaining an example of the operation of the coding device 1 according to the present embodiment.

As shown in FIG. 6, in step S101, the coding apparatus 1 determines the position of the reference pixel used when generating the predicted image according to the determined intra prediction mode, and uses the reference pixel to generate the predicted image. Generate.

In step S102, the coding device 1 generates a residual signal based on the difference between the predicted image and the original image.

In step S103, when the position of the reference pixel used to generate the predicted image includes at least one of the right side and the lower side, the coding apparatus 1 transmits the residual signal to at least one of the horizontal direction and the vertical direction. After inverting, the orthogonal transformation process is performed.

In step S104, the coding apparatus 1 selects the quadratic orthogonal transformation process to be applied from the predetermined quadratic orthogonal transform group according to the intra prediction mode and the position of the reference pixel, and the orthogonal transform coefficient. Is subjected to the selected quadratic orthogonal transformation process.

In step S105, the coding apparatus 1 performs a quantization process on the signal subjected to the quadratic orthogonal conversion process to generate a quantized conversion coefficient.

In step S106, the coding device 1 performs entropy coding processing on the flag information including the intra prediction mode and the quantized conversion coefficient, and outputs the stream.

Further, the decoding device 3 according to the present embodiment is configured to divide the original image of each frame constituting the moving image into CUs and decode it. Further, the decoding device 3 according to the present embodiment is configured so that the CU can be divided into a plurality of TUs, similarly to the coding device 1 according to the present embodiment.

As shown in FIG. 7, the decoding device 3 according to the present embodiment includes an entropy decoding unit 31, a decoding order control unit 32, a sequential decoding image generation unit 33, and a memory 34.

The entropy decoding unit 31 is configured to perform entropy decoding processing on the stream output from the coding device 1 to decode the conversion coefficient, flag information, and the like from the stream output from the coding device 1. ing. Here, the conversion coefficient is a quantized conversion coefficient obtained as a signal encoded by dividing the original image in frame units into CUs by the coding device 1.

The decoding order control unit 32 is configured to determine the decoding order of the TUs in the CU based on the intra prediction mode.

Specifically, the decoding order control unit 32 has a flag indicating whether or not the TU division output by the entropy decoding unit 31 has been performed (whether or not the CU is divided into a plurality of TUs) and an intra prediction mode. It is configured to determine the decoding order of the TUs in the CU according to the direction.

For example, in the decoding order control unit 32, similarly to the coding order control unit 13, when the CU is divided into a plurality of TUs and the direction of the intra prediction mode is from the lower left to the upper right. Decoding order of lower left TU in CU → lower right TU in CU → upper left TU in CU → upper right TU in CU, or lower left TU in CU → upper left TU in CU → in CU Of the decoding order of TU at the lower right of TU → TU at the upper right in the CU, the decoding process may be performed in a predetermined decoding order.

The sequential decoding image generation unit 33 is configured to generate a decoded image (decoded image for each TU) based on the decoding order determined by the decoding order control unit 32 and the method of dividing the CU into TUs.

Specifically, when the CU is divided into a plurality of TUs, the sequential decoding image generation unit 33 is quantized and output by the entropy decoding unit 31 according to the decoding order determined by the decoding order control unit 32. It is configured to generate a decoded image by sequentially performing inverse quantization processing, inverse orthogonal conversion processing, and intra-prediction with respect to the conversion coefficient.

As shown in FIG. 7, the sequential decoding image generation unit 33 includes an intra prediction unit 33a, an inverse quantization / inverse conversion unit 33b, and a decoding image generation unit 33c.

The intra prediction unit 33a may be configured to generate a prediction image using the intra prediction mode output by the entropy decoding unit 31 according to the decoding order determined by the decoding order control unit 32.

The inverse quantization / inverse transformation unit 33b performs the inverse quantization processing and the inverse transformation processing (for example, the inverse orthogonal transformation processing) on the quantized conversion coefficient output by the entropy decoding unit 31, and the residual. It is configured to generate a signal.

As shown in FIG. 8, the inverse quantization / inverse conversion unit 33b includes an inverse quantization unit 33b1, a quadratic inverse orthogonal transformation unit 33b2, and an inverse orthogonal transformation unit 33b3.

The inverse quantization unit 33b1 is configured to perform an inverse quantization process on the quantized conversion coefficient output by the entropy decoding unit 31.

The quadratic inverse orthogonal transform unit 33b2 is configured to perform a quadratic inverse orthogonal transform process on the signal (conversion coefficient) output from the inverse quantization unit 33b1.

Specifically, the quadratic inverse orthogonal transform unit 33b2, like the quadratic orthogonal transform unit 14c2, has a predetermined quadratic according to the intra prediction mode and the position of the reference pixel used to generate the predicted image. The quadratic inverse orthogonal transform process to be applied is selected from the inverse orthogonal transform group, and the selected quadratic inverse orthogonal transform process is applied to the signal output from the inverse quantization unit 33b1.

That is, when the intra prediction mode belongs to category B, the quadratic inverse orthogonal transform unit 33b2 applies the quadratic inverse to the quadratic inverse orthogonal transform group defined in advance according to the direction of the intra prediction mode. It may be configured to select the orthogonal transformation process.

For example, when the intra prediction mode is 18, the quadratic inverse orthogonal transform unit 33b2 applies the quadratic inverse orthogonal transform applied from the quadratic inverse orthogonal transform group defined in advance according to the direction of the intra prediction mode 18. It may be configured to select a process.

Alternatively, the quadratic inverse orthogonal transform unit 33b2 is predetermined according to the direction of the intra prediction mode when the intra prediction mode belongs to category A and the lower side is not included as the position of the reference pixel. It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group.

For example, the quadratic inverse orthogonal transform unit 33b2 is predetermined according to the direction of the intra prediction mode 2 when the intra prediction mode is 2 and the lower side is not included as the position of the reference pixel. It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group.

Alternatively, the quadratic inverse orthogonal transform unit 33b2 is predetermined according to the direction of the intra prediction mode when the intra prediction mode belongs to category C and the right side is not included as the position of the reference pixel. It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group.

For example, the quadratic inverse orthogonal transform unit 33b2 is predetermined according to the direction of the intra prediction mode 34 when the intra prediction mode is 34 and the right side is not included as the position of the reference pixel. It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group.

Further, the quadratic inverse orthogonal transform unit 33b2 of the quadratic inverse orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is vertically inverted when the lower side is included in the position of the reference pixel. It may be configured to select the quadratic inverse orthogonal transform process to be applied from among them.

That is, the quadratic inverse orthogonal transform unit 33b2 reverses the direction of the intra-prediction mode in the vertical direction when the intra-prediction mode belongs to category A and the lower side is included as the position of the reference pixel. It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group defined in advance according to the direction.

For example, when the intra-prediction mode is 2 and the lower side is included as the position of the reference pixel, the quadratic inverse orthogonal transform unit 33b2 reverses the direction of the intra-prediction mode 2 vertically ( It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group defined in advance according to the direction of the intra prediction mode 18).

Alternatively, when the position of the reference pixel includes the right side, the quadratic inverse orthogonal transform unit 33b2 of the quadratic inverse orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is reversed in the horizontal direction. It may be configured to select the quadratic inverse orthogonal transform process to be applied from among them.

That is, when the intra-prediction mode belongs to category C and the right side is included as the position of the reference pixel, the quadratic inverse orthogonal transform unit 33b2 reverses the direction of the intra-prediction mode in the horizontal direction. It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group defined in advance according to the direction.

For example, when the intra-prediction mode is 34 and the right side is included as the position of the reference pixel, the quadratic inverse orthogonal transform unit 33b2 reverses the direction of the intra-prediction mode 34 horizontally ( It may be configured to select the quadratic inverse orthogonal transform process to be applied from the quadratic inverse orthogonal transform group defined in advance according to the direction of the intra prediction mode 18).

The inverse orthogonal transform unit 33b3 is configured to perform an inverse orthogonal transform process on the signal output from the quadratic inverse orthogonal transform unit 33b2.

Specifically, when the position of the reference pixel includes at least one of the right side and the lower side, the inverse orthogonal transform unit 33b3 outputs a signal output from the secondary inverse orthogonal transform unit 33b2 at least in the horizontal direction and the vertical direction. It is configured to invert to one side and then perform an inverse orthogonal transformation process.

For example, when the position of the reference pixel includes the lower side, the inverse orthogonal transform unit 33b3 performs the inverse orthogonal transform process after inverting the signal output from the quadratic inverse orthogonal transform unit 33b2 in the vertical direction. It may be configured.

Alternatively, when the position of the reference pixel includes the right side, the inverse orthogonal transform unit 33b3 performs the inverse orthogonal transform process after inverting the signal output from the secondary inverse orthogonal transform unit 33b2 in the horizontal direction. It may be configured.

The decoded image generation unit 33c is configured to generate a decoded image by adding the predicted image generated by the intra prediction unit 33a and the residual signal generated by the inverse quantization / inverse conversion unit 33b.

The memory 34 is configured to hold the decoded image generated by the sequential decoding image generation unit 33 so that it can be used as a reference image for intra-prediction and inter-prediction.

FIG. 9 shows a flowchart for explaining an example of the operation of the decoding device 3 according to the present embodiment.

As shown in FIG. 9, in step S201, the decoding device 3 uses the intra prediction mode to generate a prediction image.

In step S202, the decoding device 3 performs an inverse quantization process on the quantized conversion coefficient.

In step S203, the decoding device 3 applies a quadratic inverse orthogonal transform process applied from a predetermined quadratic inverse orthogonal transform group according to the intra prediction mode and the position of the reference pixel used for generating the predicted image. Is selected, and the selected quadratic inverse orthogonal transformation process is applied to the signal subjected to the inverse quantization process.

In step S204, when the position of the reference pixel includes at least one of the right side and the lower side, the decoding device 3 inverts the signal subjected to the quadratic inverse orthogonal transformation process in at least one of the horizontal direction and the vertical direction. After that, the inverse orthogonal transformation process is performed.

According to the coding device 1 and the decoding device 3 according to the present embodiment, the position of the reference pixel is set with respect to the orthogonal conversion coefficient obtained by performing the orthogonal conversion process on the residual signal obtained by the intra prediction. It becomes possible to switch and use different quadratic orthogonal transformation processing groups according to the situation, the entropy can be reduced, and the coding efficiency is improved.

(Second Embodiment)
Hereinafter, the coding device 1 and the decoding device 3 according to the second embodiment of the present invention will be described focusing on the differences from the coding device 1 and the decoding device 3 according to the first embodiment described above.

In the coding apparatus 1 according to the present embodiment, the orthogonal transform unit 14c1 is generated by the residual signal generation unit 14b when at least one of the right side and the lower side is included in the position of the reference pixel used for generating the predicted image. Instead of inverting the residual signal in at least one of the horizontal and vertical directions, at least one of the bases in the horizontal and vertical directions was inverted with respect to the residual signal generated by the residual signal generation unit 14b. It is configured to perform the orthogonal transformation process above.

For example, the orthogonal transform unit 14c1 may be configured to perform the orthogonal transform process after inverting the base in the vertical direction with respect to the residual signal when the position of the reference pixel includes the lower side.

Alternatively, the orthogonal transform unit 14c1 may be configured to perform the orthogonal transform process after inverting the base in the horizontal direction with respect to the residual signal when the position of the reference pixel includes the right side.

In the coding apparatus 1 according to the present embodiment, the quadratic orthogonal transform unit 14c2 applies the quadratic orthogonal matrix from a predetermined quadratic orthogonal transform group according to the intra prediction mode and the position of the reference pixel. The conversion process is selected, and the selected quadratic orthogonal conversion process is applied to the signal (orthogonal conversion coefficient) output from the orthogonal transform unit 14c1.

For example, when the position of the reference pixel includes the lower side, the quadratic orthogonal transform unit 14c2 is selected from the quadratic orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is vertically inverted. It may be configured to select the quadratic orthogonal transformation process to be applied.

Alternatively, when the position of the reference pixel includes the right side, the quadratic orthogonal transform unit 14c2 is selected from the quadratic orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is reversed in the horizontal direction. It may be configured to select the quadratic orthogonal transformation process to be applied.

Further, in the decoding device 3 according to the present embodiment, the quadratic inverse orthogonal transform unit 33b2 performs a predetermined quadratic inverse orthogonal transform according to the intra prediction mode and the position of the reference pixel used for generating the predicted image. The quadratic inverse orthogonal transform process to be applied is selected from the group, and the selected quadratic inverse orthogonal transform process is applied to the signal output from the inverse quantization unit.

For example, the quadratic inverse orthogonal transform unit 33b2 of the quadratic inverse orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is vertically inverted when the position of the reference pixel includes the lower side. It may be configured to select the quadratic inverse orthogonal transform process to be applied from among them.

Alternatively, when the position of the reference pixel includes the right side, the quadratic inverse orthogonal transform unit 33b2 of the quadratic inverse orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is reversed in the horizontal direction. It may be configured to select the quadratic inverse orthogonal transform process to be applied from among them.

In the decoding device 3 according to the present embodiment, the inverse orthogonal transform unit 33b3 outputs a signal output from the quadratic inverse orthogonal transform unit 33b2 in the horizontal direction when at least one of the right side and the lower side is included in the position of the reference pixel. And, instead of inverting at least one in the vertical direction, the signal output from the quadratic inverse orthogonal transform unit 33b2 is subjected to the inverse orthogonal transform process after inverting at least one of the bases in the horizontal direction and the vertical direction. It is configured as follows.

For example, when the position of the reference pixel includes the lower side, the inverse orthogonal transform unit 33b3 reverses the base in the vertical direction with respect to the signal output from the secondary inverse orthogonal transform unit 33b2, and then performs the inverse orthogonal transform process. May be configured to apply.

Alternatively, when the position of the reference pixel includes the right side, the inverse orthogonal transform unit 33b3 reverses the base in the horizontal direction with respect to the signal output from the secondary inverse orthogonal transform unit 33b2, and then performs the inverse orthogonal transform process. May be configured to apply.

(Other embodiments)
As mentioned above, the invention has been described by the embodiments described above, but the statements and drawings that form part of the disclosure in such embodiments should not be understood as limiting the invention. Such disclosure will reveal to those skilled in the art various alternative embodiments, examples and operational techniques.

Further, although not particularly mentioned in the above-described embodiment, a program for causing a computer to execute each process performed by the above-mentioned coding device 1 and decoding device 3 may be provided. The program may also be recorded on a computer-readable medium. Computer-readable media can be used to install such programs on computers. Here, the computer-readable medium on which such a 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.

Alternatively, even if a chip composed of a memory for storing a program for realizing at least a part of the functions in the encoding device 1 and the decoding device 3 described above and a processor for executing the program stored in the memory is provided. Good.

1 ... Coding device 11 ... Intra prediction mode determination unit 12 ... TU division determination unit 13 ... Coding order control unit 14 ... Sequential local decoding image generation unit 14a ... Intra prediction unit 14b ... Residual signal generation unit 14c ... Orthogonal conversion Quantization unit 14c1 ... Orthogonal conversion unit 14c2 ... Secondary orthogonal conversion unit 14c3 ... Quantization unit 14d ... Inverse quantization unit / inverse orthogonal conversion unit 14e ... Local decoding Image generation unit 15 ... Memory 16 ... Entropy coding unit 3 ... Decoding Device 31 ... Entropy decoding unit 32 ... Decoding order control unit 33 ... Sequential local decoding image generation unit 33a ... Intra prediction unit 33b ... Inverse quantization / inverse conversion unit 33b1 ... Inverse quantization unit 33b2 ... Secondary inverse orthogonal transformation unit 33b3 ... Inverse orthogonal conversion unit 33c ... Decrypted image generation unit 34 ... Memory

Claims (4)

A coding device that divides the original image of each frame that constitutes a moving image into blocks and encodes them.
An intra-prediction unit that generates a prediction image corresponding to the coded target block using the intra-prediction mode,
A residual signal generation unit that generates a residual signal based on the difference between the predicted image generated by the intra prediction unit and the original image, and a residual signal generation unit.
A conversion unit that performs conversion processing on the residual signal generated by the residual signal generation unit, and a conversion unit.
It is provided with a secondary conversion unit that controls a secondary conversion process for a signal output from the conversion unit according to the position of a reference pixel used for generating the prediction image and the intra prediction mode.
The secondary conversion unit determines whether or not at least one pixel included in the pixel line adjacent to the left side of the target block and the pixel line adjacent to the upper side of the target block is used as the reference pixel in the intra prediction. A coding apparatus characterized in that the prediction mode and the secondary conversion process selected from the secondary conversion group determined according to the prediction mode are applied. It is a decoding device that decodes the original image of the frame unit that constitutes the moving image in block units obtained by dividing it.
An intra-prediction unit that uses the intra-prediction mode to generate a prediction image corresponding to the block to be decoded.
An inverse quantization unit that performs inverse quantization processing on the quantized conversion coefficient,
A secondary inverse transformation unit that controls the secondary inverse transformation processing for the signal output from the inverse quantization unit according to the intra prediction mode and the position of the reference pixel used to generate the predicted image.
A reverse conversion unit that performs reverse conversion processing on the signal output from the secondary reverse conversion unit is provided.
Whether or not the secondary inverse conversion unit uses at least one pixel included in the pixel line adjacent to the left side of the target block and the pixel line adjacent to the upper side of the target block as the reference pixel for intra-prediction. A decoding apparatus characterized in that an intra prediction mode and the secondary inverse conversion process selected from the secondary inverse conversion group determined according to the above are applied. A program for causing a computer to function as the coding device according to claim 1. A program for causing a computer to function as the decoding device according to claim 2.

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