JP2022186939A - Encoder, decoder and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2023,JPO&INPIT

Description

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

In moving picture (video) coding systems represented by H.265/HEVC (High Efficiency Video Coding), there are two methods: inter prediction using temporal correlation between frames and intra prediction using spatial correlation within frames. After performing prediction while switching the type of prediction and generating a residual signal, it is configured to perform orthogonal transform processing, loop filter processing, and entropy coding processing and output the obtained stream.

In intra prediction in HEVC, a total of 35 types of intra prediction modes, including planar prediction, DC prediction, and directional prediction, are prepared. According to the intra prediction mode determined by the encoder, intra prediction is performed using adjacent decoded reference pixels. configured to do so. Hereinafter, unless otherwise specified, the term "reference pixel" indicates a decoded reference pixel.

Here, in intra prediction in HEVC, a specified value (10 It is configured to create reference pixels to be used when generating a predicted image by filling in "512" in the case of a bit moving image).

In addition, in conventional HEVC, encoding processing is performed in raster scan order from the upper left, so there are cases where reference pixels have not been decoded. In such a case, a prediction image is generated using a value obtained by extrapolating the nearest decoded reference pixel to the 0th order.

In particular, in intra prediction in conventional HEVC, there are many cases where reference pixels located on the lower left side and upper right side of the CU have not been decoded due to encoding processing in raster scan order. However, there is a problem that the prediction accuracy is lowered and the coding efficiency is reduced when the direction prediction is performed from the direction in which there is a .

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

In addition, the intra prediction used in HEVC is prediction using spatially adjacent upper or left reference pixels. Pixel accuracy tends to be low (see FIG. 10).

In the drawings of this specification, the arrow indicating the direction of the intra prediction mode (prediction direction) is directed from the target pixel for intra prediction to the reference pixel, as described in the HEVC standard (the same applies hereinafter). .

Conventional HEVC utilizes this property to perform discrete sine transform (DST) or discrete cosine transform (DCT) in the horizontal and vertical directions from the left side and the upper side where the reference pixel is located. 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 has an asymmetrical shape in which one end point is closed and the other end point is widened. Entropy can be effectively reduced by applying DST according to the signal strength of the residual signal.

By the way, in non-patent document 2, in orthogonal transform processing (DCT and DST) applied in conventional HEVC, secondary orthogonal transform processing (hereinafter referred to as quadratic orthogonal A technique for efficiently reducing entropy by applying transformation processing) is disclosed.

Specifically, in the technique described in Non-Patent Document 2, after conventional orthogonal transform processing is applied to residual signals obtained by intra prediction, the obtained orthogonal transform coefficients are divided into small blocks. It is configured to divide and apply quadratic orthogonal transform processing block by block.

Here, the encoding apparatus selects an optimum quadratic orthogonal transform process from among a group of quadratic orthogonal transform processes (a set of quadratic orthogonal transform processes) for which a plurality of types of bases are prepared, and Output as a stream the flag information indicating the quadratic orthogonal transform processing (if not applying the quadratic orthogonal transform processing is optimal, output the flag information indicating that the quadratic orthogonal transform processing is not applied as a stream) It is configured.

Further, in the technique described in Non-Patent Document 2, the characteristics of the residual signal and the characteristics of the orthogonal transform coefficients differ depending on the direction of the intra prediction mode. It is configured to switch treatment groups.

As a result, it becomes possible to select the optimal quadratic orthogonal transform processing from among the quadratic orthogonal transform processing groups specified for each intra prediction mode, and the amount of information required for the flag indicating which quadratic orthogonal transform processing was used. It is possible to reduce

Mochizuki et al., "Applied intra-prediction method based on mean value coordinates", Information Processing Society of Japan research report, vol, 2012-AVM-77, No.12 X. Zhao, J. Chen, M. Karczewicz, "Mode-dependent non-separable secondary transform", ITU-T SG16/Q6 Doc. COM16-C1044, October 2015.

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

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

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

Accordingly, the present invention has been made to solve the above-described problems, and provides an encoding device, a decoding device, and a program capable of efficiently reducing entropy and improving encoding performance in intra prediction. intended to provide

A first feature of the present invention is an encoding device that is configured to divide and encode an original image in units of frames that constitute a moving image into encoding target blocks, and uses an intra prediction mode to encode an intra predictor configured to generate a predicted image; and a residual signal configured to generate a residual signal by a difference between the predicted image generated by the intra predictor and the original image. generating unit, and generating the residual signal generated by the residual signal generating unit in at least the horizontal direction and the vertical direction when the positions of the reference pixels used for generating the predicted image include at least one of the right side and the lower side; Among the quadratic orthogonal transform groups defined in advance according to the orthogonal transform unit configured to perform the orthogonal transform processing after inverting to one side, and the intra prediction mode and the position of the reference pixel a quadratic orthogonal transform unit configured to select a quadratic orthogonal transform process to be applied from and to perform the selected quadratic orthogonal transform process on the signal output from the orthogonal transform unit This is the gist of it.

A second feature of the present invention is a decoding device configured to divide an original image in units of frames constituting a moving image into encoding target blocks and decode the predicted image using an intra prediction mode. an intra prediction unit configured to generate an inverse quantization unit configured to perform inverse quantization processing on the quantized transform coefficients; the intra prediction mode and the predicted image Selects the secondary inverse orthogonal transform process to be applied from the predefined secondary inverse orthogonal transform group according to the position of the reference pixel used for generating the On the other hand, a secondary inverse orthogonal transform unit configured to perform the selected secondary inverse orthogonal transform processing, and a secondary inverse orthogonal transform unit that performs the secondary An inverse orthogonal transform unit configured to perform inverse orthogonal transform processing after inverting a signal output from the inverse orthogonal transform unit in at least one of the horizontal direction and the vertical direction.

A third feature of the present invention is an encoding device configured to divide and encode an original image in units of frames constituting a moving image into encoding target blocks, wherein the intra prediction mode is used to encode an intra predictor configured to generate a predicted image; and a residual signal configured to generate a residual signal by a difference between the predicted image generated by the intra predictor and the original image. generating unit, and horizontal direction and vertical direction for the residual signal generated by the residual signal generating unit when at least one of the right side and the lower side is included in the position of the reference pixel used to generate the predicted image. An orthogonal transform unit configured to perform orthogonal transform processing after inverting the basis of at least one of the directions, and a predetermined quadratic transform according to the intra prediction mode and the position of the reference pixel. A quadratic orthogonal transform configured to select a quadratic orthogonal transform process to be applied from an orthogonal transform group and apply the selected quadratic orthogonal transform process to a signal output from the orthogonal transform unit. The gist is to comprise a part.

A fourth feature of the present invention is a decoding device configured to divide an original image in units of frames constituting a moving image into encoding target blocks and decode the predicted image using an intra prediction mode. an intra prediction unit configured to generate an inverse quantization unit configured to perform inverse quantization processing on the quantized transform coefficients; the intra prediction mode and the predicted image Selects the secondary inverse orthogonal transform process to be applied from the predefined secondary inverse orthogonal transform group according to the position of the reference pixel used for generating the On the other hand, a secondary inverse orthogonal transform unit configured to perform the selected secondary inverse orthogonal transform processing, and a secondary inverse orthogonal transform unit that performs the secondary an inverse orthogonal transform unit configured to perform inverse orthogonal transform processing on the signal output from the inverse orthogonal transform unit after inverting at least one of the bases in the horizontal direction and the vertical direction; is the gist.

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

A gist of a sixth aspect of the present invention is a program for causing a computer to function as the decryption device according to the above-described second and fourth aspects.

Advantageous Effects of Invention According to the present invention, it is possible to provide an encoding device, a decoding device, and a program capable of efficiently reducing entropy and improving encoding performance in intra prediction.

FIG. 1 is a diagram showing an example of functional blocks of an encoding device 1 according to the first embodiment. FIG. 2 is a diagram showing an example of functional blocks of the orthogonal transform/quantization unit 14c of the encoding device 1 according to the first embodiment. FIG. 3 is a diagram showing an example of directions of intra prediction modes used in the first embodiment. FIG. 4 is a diagram illustrating an example of a predicted image generation method according to the first embodiment. FIG. 5 is a diagram illustrating an example of a predicted image generation method according to the first embodiment. FIG. 6 is a flow chart showing an example of the operation of the encoding device 1 according to the first embodiment. FIG. 7 is a diagram showing an example of functional blocks of the decoding device 3 according to the first embodiment. FIG. 8 is a diagram showing an example of functional blocks of the inverse quantization/inverse transform unit 33b of the decoding device 3 according to the first embodiment. FIG. 9 is a flow chart showing an example of the operation of the decoding device 3 according to the first embodiment. FIG. 10 is a diagram for explaining the conventional technology. FIG. 11 is a diagram for explaining the conventional technology. FIG. 12 is a diagram for explaining the conventional technology.

(First embodiment)
An encoding device 1 and a decoding device 3 according to the first embodiment of the present invention will be described below with reference to FIGS. 1 to 9. FIG.

Here, the encoding device 1 and the decoding device 3 according to this embodiment are configured to support intra prediction in a video encoding method such as HEVC. Note that the encoding device 1 and the decoding device 3 according to the present embodiment are configured to be compatible with any video encoding method as long as it is a video encoding method that performs intra prediction.

The encoding device 1 according to the present embodiment is configured to divide an original image in units of frames constituting a moving image into CUs and encode the CUs. Also, the encoding device 1 according to the present embodiment may be configured to be able to divide a CU into a plurality of TUs. Hereinafter, in the present embodiment, a case in which a CU is divided into a plurality of TUs will be described as an example. It is also applicable to cases involving the lower side and the right side.

Note that, in the present embodiment, a CU to be encoded that does not have an adjacent decoded reference pixel, such as the CU located at the upper leftmost position in the frame, has a prescribed value ("512" for a 10-bit moving image). is configured to generate reference pixels used when generating a predicted image by filling in, all pixels adjacent to the left side of the CU to be coded can be used as reference pixels.

As shown in FIG. 1, the encoding device 1 according to the present embodiment includes an intra prediction mode determination unit 11, a TU partition determination unit 12, a coding order control unit 13, a sequential local decoded image generation unit 14, It comprises 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 apply to the CU.

The TU partition decision unit 12 is configured to decide whether to partition a CU into a plurality of TUs. In this embodiment, as a method of dividing a CU into a plurality of TUs, a case of 4 divisions is described as an example. , is not limited to such cases.

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

For example, when the TU division determination unit 12 determines to divide a CU into a plurality of TUs, the coding order control unit 13 determines that the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is from the lower left to If the direction is to the upper right (i.e., the directional prediction is performed from the lower left to the upper right), the encoding order of the TUs in the CU is the lower left TU in the CU, instead of the conventional raster scan order. Lower right TU in CU → Upper left TU in CU → Upper right TU in CU → Lower left TU in CU → Upper left TU in CU → Lower right TU in CU → It may be configured to adopt a predetermined encoding order among the encoding orders of the upper right TU in the CU.

The sequential locally decoded image generation unit 14 is configured to generate a locally decoded image (a 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, when the TU division determination unit 12 determines to divide the CU into a plurality of TUs, the sequential locally decoded image generation unit 14 follows the coding order determined by the coding order control unit 13. , is configured to sequentially generate a locally decoded image.

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

The intra prediction unit 14 a is configured to generate a predicted 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 positions of reference pixels used when generating a predicted image according to the intra prediction mode, and generate the predicted image using the reference pixels.

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

The residual signal generation unit 14b is configured to generate a residual signal from 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 transformation processing and quantization processing on the residual signal generated by the residual signal generation unit 14b, and generate quantized transform coefficients. .

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

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

Specifically, the orthogonal transform unit 14c1 performs prediction using reference pixels adjacent to at least one of the right side and the bottom side when at least one of the right side and the bottom side is included in the position of the reference pixel used to generate the predicted image. image), the residual signal generated by the residual signal generator 14b is inverted in at least one of the horizontal direction and the vertical direction, and then subjected to orthogonal transform processing to obtain orthogonal transform coefficients. It is configured.

For example, the orthogonal transform unit 14c1 vertically inverts the residual signal and It may be configured to perform the orthogonal transform processing.

Alternatively, when the right side is included in the position of the reference pixel (when the predicted image is generated using the reference pixel adjacent to the right side), the orthogonal transform unit 14c1 inverts the residual signal in the horizontal direction and converts it into an orthogonal image. It may be configured to perform conversion processing.

The quadratic orthogonal transform unit 14c2 selects a quadratic orthogonal transform process to be applied from a predefined quadratic orthogonal transform group according to the intra prediction mode and the position of the reference pixel, It is configured to apply selected quadratic orthogonal transform processing to the output signal (orthogonal transform coefficient).

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

In this 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 examples using other intra prediction modes.

Here, the quadratic orthogonal transform processing is transform processing applied to further reduce the entropy of the orthogonal transform coefficients obtained by applying the orthogonal transform processing to the residual signal.

Note that the energy distribution of the residual signal is statistically proportional to the distance from the reference pixel used for intra prediction. Therefore, the energy distribution of the residual signal differs between the intra prediction mode using only the reference pixels located on the left side and the intra prediction mode using the reference pixels located on the left side and above. In addition, the energy distribution of orthogonal transform coefficients obtained by applying orthogonal transform 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 transform coefficients and the direction of the intra prediction mode, and selectable quadratic orthogonal It is configured to switch conversion processing groups.

FIGS. 4(a) and 4(b) show examples of the energy distribution of the residual signal as intra prediction mode 2 (intra prediction mode using only reference pixels located on the left side) and intra prediction mode 18 (intra prediction mode using only reference pixels located on the left side) in HEVC. and intra-prediction modes using upper reference pixels).

However, as shown in FIG. 5 , when directional prediction in intra prediction mode 2 is performed using reference pixels positioned on the left side and lower side, directional prediction in intra prediction mode 2 is performed using only the reference pixels positioned 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.

The energy distribution (see FIG. 5) of the residual signal by directional prediction in intra prediction mode 2 using the reference pixels positioned on the left and the bottom is shown in FIG. The energy distribution is the same as that obtained by vertically inverting the residual signal resulting from the directional prediction of the intra prediction mode 18 .

That is, when performing directional prediction in intra prediction mode 2, when the position of the reference pixel includes the left side and the lower side, and the residual signal is inverted in the vertical direction and the orthogonal transform processing is applied, When performing directional prediction in intra prediction mode 18, the energy distribution of the orthogonal transform coefficients obtained is such that when the positions of the reference pixels include the left side and the upper side, the residual signal is not horizontally and vertically inverted. The energy distribution of orthogonal transform coefficients obtained when orthogonal transform processing is applied is the same (see FIGS. 4B and 5).

Since the energy distribution of orthogonal transform coefficients obtained by orthogonal transform processing on residual signals from directional prediction in intra prediction mode 2 differs depending on the positions of reference pixels used for intra prediction, the two applicable Determining the next orthogonal transform process group may increase entropy and degrade coding performance.

Therefore, the quadratic orthogonal transform unit 14c2 is not the direction of the intra prediction mode, but 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. It is configured to use the next order orthogonal transform processing group.

That is, when the intra prediction mode belongs to category B, the quadratic orthogonal transform unit 14c2 applies quadratic orthogonal transform processing from among 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 quadratic orthogonal transform group predefined according to the direction of the intra prediction mode 18. may be configured to

Alternatively, the quadratic orthogonal transform unit 14c2 is defined in advance according to the direction of the intra prediction mode when the intra prediction mode belongs to category A and the position of the reference pixel does not include the lower side. The quadratic orthogonal transform processing to be applied may be selected from among the quadratic orthogonal transform group.

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

Alternatively, if the intra prediction mode belongs to category C and the right side is not included as the position of the reference pixel, the quadratic orthogonal transform unit 14c2 is defined in advance according to the direction of the intra prediction mode. The quadratic orthogonal transform processing to be applied may be selected from among the quadratic orthogonal transform group.

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

Further, when the position of the reference pixel includes the lower side, the quadratic orthogonal transform unit 14c2 selects from among 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 transform process to be applied.

Here, "reversing the direction of the intra prediction mode in the vertical direction" means converting between the directions of intra prediction modes 2 to 9 and the directions of intra prediction modes 18 to 11, 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 linearly symmetrical positional relationship with respect to the direction of the intra prediction mode 10 .

That is, when the intra prediction mode belongs to category A, and when the position of the reference pixel includes the lower side, the quadratic orthogonal transform unit 14c2 converts the direction of the intra prediction mode to the direction reversed in the vertical direction. The secondary orthogonal transform processing to be applied may be selected from a group of quadratic orthogonal transforms predefined according to .

For example, when the intra prediction mode is 2 and the lower side is included as the position of the reference pixel, the quadratic orthogonal transform unit 14c2 performs a direction obtained by vertically reversing the direction of intra prediction mode 2 (intra prediction mode). 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 right side is included in the position of the reference pixel, the quadratic orthogonal transform unit 14c2 selects from among the quadratic orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is horizontally inverted. It may be configured to select the quadratic orthogonal transform process to be applied.

Here, "reversing the direction of the intra prediction mode horizontally" means converting between the direction of the intra prediction modes 18 to 25 and the direction of the intra prediction modes 34 to 27 in the example of FIG. That is, it means that the direction of each intra prediction mode is converted to the direction of the intra prediction mode having a linearly symmetrical positional relationship with respect 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 performs the direction in which the direction of the intra prediction mode is reversed in the horizontal direction. The secondary orthogonal transform processing to be applied may be selected from a group of quadratic orthogonal transforms predefined according to .

For example, when the intra prediction mode is 34 and the right side is included as the position of the reference pixel, the quadratic orthogonal transform unit 14c2 performs a direction obtained by horizontally reversing the direction of the intra prediction mode 34 (intra prediction mode). 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 quantization processing on the signal output from the quadratic orthogonal transform unit 14c2 and generate quantized transform coefficients.

The inverse quantization unit/inverse orthogonal transform unit 14d again performs the inverse quantization process, the secondary inverse orthogonal transform process, and the inverse orthogonal transform process on the quantized transform coefficients generated by the orthogonal transform/quantization unit 14c. to generate a residual signal.

The local decoded image generation unit 14e generates a local decoded image by adding the predicted image generated by the intra prediction unit 14a to the residual signal generated by the inverse quantization unit/inverse orthogonal transformation unit 14d. It is configured.

The memory 15 is configured to retain locally decoded images generated by the sequential local decoded image generator 14 so as to be usable as reference images.

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

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

As shown in FIG. 6, in step S101, the encoding device 1 determines the positions of reference pixels used when generating a predicted image according to the determined intra prediction mode, and uses the reference pixels to generate a predicted image. Generate.

In step S102, the encoding device 1 generates a residual signal from the difference between the predicted image and the original image.

In step S103, if the position of the reference pixel used to generate the predicted image includes at least one of the right side and the bottom side, the encoding device 1 converts the residual signal to at least one of the horizontal direction and the vertical direction. Orthogonal transformation processing is applied after inversion.

In step S104, the encoding device 1 selects a quadratic orthogonal transform process to be applied from a predefined quadratic orthogonal transform group according to the intra prediction mode and the position of the reference pixel, is subjected to the selected quadratic orthogonal transformation process.

In step S105, the encoding device 1 performs quantization processing on the signal subjected to the quadratic orthogonal transform processing to generate quantized transform coefficients.

In step S106, the encoding device 1 performs entropy encoding processing on the flag information including the intra prediction mode and the quantized transform coefficients, and outputs them as a stream.

Further, the decoding device 3 according to the present embodiment is configured to divide an original image of each frame constituting a moving image into CUs and decode the CUs. Also, the decoding device 3 according to this embodiment is configured to be able to divide a CU into a plurality of TUs, like the encoding device 1 according to this embodiment.

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

The entropy decoding unit 31 is configured to decode transform coefficients, flag information, and the like from the stream output from the encoding device 1 by performing entropy decoding processing on the stream output from the encoding device 1. ing. Here, the transform coefficients are quantized transform coefficients obtained by the encoding apparatus 1 as signals encoded by dividing the original image in units of frames into CUs.

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

Specifically, the decoding order control unit 32 uses 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 the intra prediction mode. The direction is configured to determine the decoding order of the TUs within the CU.

For example, similar to the encoding order control unit 13, the decoding order control unit 32, 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, The decoding order of the lower left TU within the CU→the lower right TU within the CU→the upper left TU within the CU→the upper right TU within the CU, or the lower left TU within the CU→the upper left TU within the CU→the inside of the CU The decoding process may be performed in a predetermined decoding order from the lower right TU in the CU to the upper right TU in the CU.

The sequentially decoded image generation unit 33 is configured to generate a decoded image (a 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 decoded image generation unit 33 follows the decoding order determined by the decoding order control unit 32 to generate the quantized quantized data output by the entropy decoding unit 31. A decoded image is generated by successively performing inverse quantization processing, inverse orthogonal transformation processing, and intra prediction on the obtained transform coefficients.

As shown in FIG. 7, the sequentially decoded image generation unit 33 includes an intra prediction unit 33a, an inverse quantization/inverse transform unit 33b, and a decoded image generation unit 33c.

The intra prediction unit 33 a 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 transform unit 33b performs inverse quantization processing and inverse transform processing (for example, inverse orthogonal transform processing) on the quantized transform coefficients output from the entropy decoding unit 31, thereby generating a residual configured to generate a signal;

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

The inverse quantization unit 33b1 is configured to perform inverse quantization processing on the quantized transform coefficients output from the entropy decoding unit 31. FIG.

The secondary inverse orthogonal transform section 33b2 is configured to perform secondary inverse orthogonal transform processing on the signal (transform coefficient) output from the inverse quantization section 33b1.

Specifically, the quadratic inverse orthogonal transform unit 33b2, similarly to the quadratic orthogonal transform unit 14c2, uses a predefined quadratic transform unit 33b2 according to the intra prediction mode and the position of the reference pixel used to generate the predicted image. A secondary inverse orthogonal transform process to be applied is selected from the inverse orthogonal transform group, and the selected secondary inverse orthogonal transform process is performed on the signal output from the inverse quantization section 33b1.

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

For example, when the intra prediction mode is 18, the secondary inverse orthogonal transform unit 33b2 applies the secondary inverse orthogonal transform from the group of secondary inverse orthogonal transforms predefined according to the direction of the intra prediction mode 18. It may be configured to select a treatment.

Alternatively, the secondary inverse orthogonal transform unit 33b2 is defined in advance 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. The secondary inverse orthogonal transform processing to be applied may be selected from the secondary inverse orthogonal transform group.

For example, the secondary inverse orthogonal transform unit 33b2 is defined in advance according to the direction of intra prediction mode 2 when the intra prediction mode is 2 and the position of the reference pixel does not include the lower side. It may be configured to select a quadratic inverse orthogonal transform process to be applied from a quadratic inverse orthogonal transform group.

Alternatively, if the intra prediction mode belongs to category C and the right side is not included as the position of the reference pixel, the secondary inverse orthogonal transform unit 33b2 is defined in advance according to the direction of the intra prediction mode. The secondary inverse orthogonal transform processing to be applied may be selected from the secondary inverse orthogonal transform group.

For example, the secondary inverse orthogonal transform unit 33b2 is defined in advance 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 a quadratic inverse orthogonal transform process to be applied from a quadratic inverse orthogonal transform group.

In addition, when the position of the reference pixel includes the lower side, the secondary inverse orthogonal transform unit 33b2 performs a predetermined secondary inverse orthogonal transform group according to the direction obtained by vertically inverting the direction of the intra prediction mode. It may be configured to select the quadratic inverse orthogonal transform process to be applied from among them.

That is, the secondary 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. The secondary inverse orthogonal transform process to be applied may be selected from a group of secondary inverse orthogonal transforms 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 secondary inverse orthogonal transform unit 33b2 performs the direction in which the direction of the intra prediction mode 2 is reversed in the vertical direction ( The secondary inverse orthogonal transform process to be applied may be selected from a group of secondary inverse orthogonal transforms defined in advance according to the direction of the intra prediction mode 18).

Alternatively, when the right side is included in the position of the reference pixel, the secondary inverse orthogonal transform unit 33b2 performs a predetermined secondary inverse orthogonal transform group according to the horizontally inverted direction of the intra prediction mode. 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 secondary inverse orthogonal transform unit 33b2 horizontally reverses the direction of the intra prediction mode. The secondary inverse orthogonal transform process to be applied may be selected from a group of secondary inverse orthogonal transforms 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 performs the direction in which the direction of the intra prediction mode 34 is reversed in the horizontal direction ( The secondary inverse orthogonal transform process to be applied may be selected from a group of secondary inverse orthogonal transforms defined in advance according to the direction of the intra prediction mode 18).

The inverse orthogonal transform section 33b3 is configured to perform inverse orthogonal transform processing on the signal output from the secondary inverse orthogonal transform section 33b2.

Specifically, when the position of the reference pixel includes at least one of the right side and the bottom side, the inverse orthogonal transformation unit 33b3 converts the signal output from the secondary inverse orthogonal transformation unit 33b2 into at least one of the horizontal direction and the vertical direction. It is configured to perform inverse orthogonal transform processing after inverting to one side.

For example, when the position of the reference pixel includes the lower side, the inverse orthogonal transformation unit 33b3 vertically inverts the signal output from the secondary inverse orthogonal transformation unit 33b2 and then performs the inverse orthogonal transformation process. may be configured.

Alternatively, when the right side is included in the position of the reference pixel, the inverse orthogonal transformation unit 33b3 horizontally inverts the signal output from the secondary inverse orthogonal transformation unit 33b2 and then performs the inverse orthogonal transformation process. may be configured.

The decoded image generator 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 transform unit 33b.

The memory 34 is configured to hold the decoded images generated by the sequential decoded image generation unit 33 so that they can be used as reference images 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 this embodiment.

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

In step S202, the decoding device 3 performs inverse quantization processing on the quantized transform coefficients.

In step S203, the decoding device 3 performs secondary inverse orthogonal transform processing to be applied from a predetermined secondary 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 transform process is performed on the signal that has been subjected to the inverse quantization process.

In step S204, if the position of the reference pixel includes at least one of the right side and the bottom side, the decoding device 3 inverts the signal subjected to the secondary inverse orthogonal transform processing in at least one of the horizontal direction and the vertical direction. After that, inverse orthogonal transform processing is applied.

According to the encoding device 1 and the decoding device 3 according to the present embodiment, the orthogonal transform coefficient obtained by performing the orthogonal transform process on the residual signal obtained by intra prediction is set to the position of the reference pixel. Accordingly, different quadratic orthogonal transform processing groups can be switched and used, entropy can be reduced, and coding efficiency can be improved.

(Second embodiment)
An encoding device 1 and a decoding device 3 according to the second embodiment of the present invention will be described below, focusing on differences from the encoding device 1 and the decoding device 3 according to the above-described first embodiment.

In the encoding device 1 according to the present embodiment, the orthogonal transform unit 14c1 generates a Instead of inverting the residual signal in at least one of the horizontal and vertical directions, the basis of at least one of the horizontal and vertical directions is inverted for the residual signal generated by the residual signal generation unit 14b. It is configured to perform orthogonal transform processing on the above.

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

Alternatively, the orthogonal transform unit 14c1 may be configured to perform orthogonal transform processing after inverting the horizontal base of the residual signal when the right side is included in the position of the reference pixel.

In the encoding device 1 according to the present embodiment, the quadratic orthogonal transform unit 14c2 applies a quadratic orthogonal transform from a predetermined quadratic orthogonal transform group according to the intra prediction mode and the position of the reference pixel. It is configured to select a transform process and apply the selected quadratic orthogonal transform process to the signal (orthogonal transform coefficient) output from the orthogonal transform section 14c1.

For example, when the position of the reference pixel includes the lower side, the quadratic orthogonal transform unit 14c2 selects from among 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 transform process to be applied.

Alternatively, when the right side is included in the position of the reference pixel, the quadratic orthogonal transform unit 14c2 selects from among the quadratic orthogonal transform group defined in advance according to the direction in which the direction of the intra prediction mode is horizontally inverted. It may be configured to select the quadratic orthogonal transform process to be applied.

Further, in the decoding device 3 according to the present embodiment, the secondary inverse orthogonal transform unit 33b2 performs a predetermined secondary inverse orthogonal transform according to the intra prediction mode and the position of the reference pixel used for generating the predicted image. A 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, when the position of the reference pixel includes the lower side, the secondary inverse orthogonal transform unit 33b2 performs a predetermined secondary inverse orthogonal transform group 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 inverse orthogonal transform process to be applied from among them.

Alternatively, when the right side is included in the position of the reference pixel, the secondary inverse orthogonal transform unit 33b2 performs a predetermined secondary inverse orthogonal transform group according to the horizontally inverted direction of the intra prediction mode. 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 converts the signal output from the secondary 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 in at least one of the vertical directions, the signal output from the secondary inverse orthogonal transform unit 33b2 is subjected to inverse orthogonal transform processing after inverting at least one base in the horizontal direction and vertical direction. is configured as

For example, when the lower side is included in the position of the reference pixel, the inverse orthogonal transform unit 33b3 performs inverse orthogonal transform processing after inverting the base in the vertical direction for the signal output from the secondary inverse orthogonal transform unit 33b2. may be configured to apply

Alternatively, when the right side is included in the position of the reference pixel, the inverse orthogonal transform unit 33b3 inverts the base in the horizontal direction of 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 noted above, the present invention has been described through the above-described embodiments, but the statements and drawings forming part of the disclosure in such embodiments should not be understood to limit the present invention. From such disclosure, various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art.

Moreover, although not particularly mentioned in the above-described embodiment, a program may be provided that causes a computer to execute each process performed by the above-described encoding device 1 and decoding device 3 . Also, such a program may be recorded on a computer-readable medium. Such programs can be installed on a computer using a computer readable medium. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

Alternatively, a chip configured by a memory storing a program for realizing at least part of the functions in the encoding device 1 and the decoding device 3 described above and a processor executing the program stored in the memory may be provided. good.

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

Claims (4)

An encoding device that encodes a frame-based original image that constitutes a moving image by dividing it into blocks,
an intra prediction unit that generates a predicted image using an intra prediction mode that indicates the type of intra prediction processing;
a residual signal generation unit that generates a residual signal from a difference between the predicted image generated by the intra prediction unit and the original image;
a conversion unit that performs conversion processing on the residual signal generated by the residual signal generation unit;
a secondary conversion unit that controls secondary conversion processing for the signal output from the conversion unit according to the position of the reference pixel used to generate the predicted image and the intra prediction mode;
An encoding device characterized by comprising: A decoding device for decoding in units of blocks obtained by dividing an original image in units of frames constituting a moving image,
an intra prediction unit that generates a predicted image using an intra prediction mode that indicates the type of intra prediction processing;
an inverse quantization unit that performs inverse quantization processing on the quantized transform coefficients;
a secondary inverse transform unit that controls secondary inverse transform 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 decoding device characterized by comprising: A program for causing a computer to function as the encoding 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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