JP2024069638A - Prediction device, encoding device, decoding device, and program - Google Patents

Abstract

[Problem] Even when multiple synthesis methods are introduced into triangular decomposition prediction, an increase in the amount of flags to be signaled is suppressed. [Solution] A prediction device that performs prediction in units of blocks obtained by dividing an image includes a division unit that divides a block to be predicted by lines and outputs multiple prediction regions, a generation unit that generates multiple regional prediction images corresponding to the multiple prediction regions, a determination unit that determines from multiple methods a synthesis method to be used to synthesize the multiple regional prediction images, and a synthesis unit that synthesizes the multiple regional prediction images using the synthesis method determined by the determination unit, and outputs a prediction block corresponding to the block to be predicted. [Selected Figure] Figure 2

Description

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

In a video (image) coding method, the coding device divides the original image into blocks, predicts the block to be coded by switching between inter prediction, which uses the temporal correlation between frames, and intra prediction, which uses the spatial correlation within a frame, and performs conversion, quantization, and entropy coding on the prediction residual, which represents the difference between the predicted block and the block to be coded, and outputs coded data in the form of a bitstream.

Versatile Video Coding (VVC), a next-generation coding method, employs triangular partitioning prediction (TPM: Triangle Partitioning Mode) as one of the inter-prediction modes. TPM divides the coding target block diagonally, assigning motion vectors to each area, and performs motion compensation prediction.

In TPM, for predicted images near region boundaries, a mixing process (called blending) is performed in which predicted images for each region are mixed using weighted synthesis (weighted average) according to their position, thereby suppressing discontinuity caused by motion prediction compensation for each region. In sequences that contain many flat regions and edges, such as screen content, blending can cause edge blurring. For this reason, Non-Patent Document 1 introduces a non-blending mode in TPM prediction that synthesizes predicted images without blending.

JVET-O1172, "Non-CE4/8: On disabling blending process in TPM"

When multiple blending modes (multiple blending methods) are introduced in a TPM as in Non-Patent Document 1, a flag indicating which mode is to be used must be signaled from the encoding side to the decoding side. This increases the number of flags to be signaled, resulting in a problem of reduced coding efficiency.

The present invention aims to provide a prediction device, an encoding device, a decoding device, and a program that can suppress an increase in the amount of flags signaled even when multiple synthesis methods are introduced into split prediction.

The prediction device according to the first aspect is a prediction device that performs prediction in units of blocks obtained by dividing an image, and includes a division unit that divides a prediction target block by straight lines and outputs a plurality of prediction regions, a generation unit that generates a plurality of regional prediction images corresponding to the plurality of prediction regions, a determination unit that determines a synthesis method to be used for synthesizing the plurality of regional prediction images from a plurality of methods, and a synthesis unit that synthesizes the plurality of regional prediction images using the synthesis method determined by the determination unit, and outputs a prediction block corresponding to the prediction target block.

The encoding device according to the second aspect is characterized in that it includes the prediction device according to the first aspect.

The decoding device according to the third aspect is characterized in that it includes the prediction device according to the first aspect.

The gist of the program according to the fourth aspect is to cause a computer to function as the prediction device according to the first aspect.

The present invention provides a prediction device, an encoding device, a decoding device, and a program that can suppress an increase in the amount of flags signaled, even when multiple synthesis methods are introduced into split prediction.

FIG. 1 is a diagram illustrating a configuration of an encoding device according to an embodiment. FIG. 2 is a diagram illustrating a configuration of a triangular decomposition prediction unit of an encoding device according to an embodiment. 11A and 11B are diagrams illustrating an operation of a division unit according to the embodiment. 6A and 6B are diagrams illustrating operations of a calculation unit and a determination unit according to the embodiment. 6A and 6B are diagrams illustrating an operation of a synthesis unit according to the embodiment. FIG. 2 is a diagram illustrating a configuration of a decoding device according to an embodiment. FIG. 2 is a diagram illustrating a configuration of a triangular decomposition prediction unit of a decoding device according to an embodiment. FIG. 11 is a diagram showing an operation flow of a triangulation prediction unit according to the embodiment.

An encoding device and a decoding device according to an embodiment will be described with reference to the drawings. The encoding device and the decoding device according to an embodiment respectively encode and decode moving images as represented by MPEG. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

<Structure of the Encoding Device>
First, the configuration of the encoding device according to this embodiment will be described. Fig. 1 is a diagram showing the configuration of an encoding device 1 according to this embodiment. The encoding device 1 is a device that performs encoding in units of blocks obtained by dividing an image.

As shown in FIG. 1, the encoding device 1 includes a block division unit 100, a subtraction unit 110, a transformation and quantization unit 120, an entropy encoding unit 130, an inverse quantization and inverse transformation unit 140, a synthesis unit 150, a memory 160, and a prediction unit 170.

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

The block division unit 100 performs block division on the luminance signal and the color difference signal. In the following, the case where the shape of the block division is the same for the luminance signal and the color difference signal will be mainly described, but it may be possible to control the division independently for the luminance signal and the color difference signal. When there is no particular distinction between the luminance block and the color difference block, they are simply referred to as the block to be coded.

The subtraction unit 110 calculates a prediction residual that represents the difference (error) between the block to be coded output by the block division unit 100 and a predicted block obtained by predicting the block to be coded by the prediction unit 170. The subtraction unit 110 calculates the prediction residual by subtracting each pixel value of the predicted block from each pixel value of the block, and outputs the calculated prediction residual to the transformation/quantization unit 120.

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

The transform unit 121 performs a transform process on the prediction residual output by the subtraction unit 110 to calculate a transform coefficient for each frequency component, and outputs the calculated transform coefficient to the quantization unit 122. The transform process (transformation) refers to a process of converting a pixel domain signal into a frequency domain signal, such as discrete cosine transform (DCT), discrete sine transform (DST), Karhunen-Loeb transform (KLT), and transforms that convert these to integers.

The quantization unit 122 quantizes the transform coefficients output by the transform unit 121 using a quantization parameter (Qp) and a quantization matrix, and outputs the quantized transform coefficients to the entropy coding unit 130 and the inverse quantization and inverse transform unit 140. Note that the quantization parameter (Qp) is a parameter that is commonly applied to each transform coefficient in a block and determines the coarseness of quantization. The quantization matrix is a matrix whose elements are the quantization values used when quantizing each transform coefficient.

The entropy coding unit 130 performs entropy coding on the transform coefficients output by the quantization unit 122, compresses the data, generates a coded stream (bit stream), and outputs the coded stream to the outside of the coding device 1. For entropy coding, Huffman codes and CABAC (Context-based Adaptive Binary Arithmetic Coding) can be used. The entropy coding unit 130 obtains information on the size and shape of each block to be coded from the block division unit 100, obtains prediction information (e.g., prediction mode and motion vector information) from the prediction unit 170, and also codes this information.

The inverse quantization and inverse transform unit 140 performs inverse quantization and inverse transform processing on a block-by-block basis. The inverse quantization and inverse transform unit 140 includes an inverse quantization unit 141 and an inverse transform unit 142.

The inverse quantization unit 141 performs an inverse quantization process corresponding to the quantization process performed by the quantization unit 122. Specifically, the inverse quantization unit 141 restores the transform coefficients by inverse quantizing the transform coefficients output by the quantization unit 122 using a quantization parameter (Qp) and a quantization matrix, and outputs the restored transform coefficients to the inverse transform unit 142.

The inverse transform unit 142 performs an inverse transform process corresponding to the transform process performed by the transform unit 121. For example, if the transform unit 121 performs a DCT, the inverse transform unit 142 performs an inverse DCT. The inverse transform unit 142 performs an inverse transform process on the transform coefficients output by the inverse quantization unit 141 to restore the prediction residual, and outputs the restored prediction residual, which is the restored prediction residual, to the synthesis unit 150.

The synthesis unit 150 synthesizes the reconstructed prediction residual output by the inverse transform unit 142 with the predicted block output by the prediction unit 170 on a pixel-by-pixel basis. The synthesis unit 150 adds each pixel value of the reconstructed prediction residual to each pixel value of the predicted block to reconstruct (decode) the block to be coded, and outputs the reconstructed decoded image (reconstructed block) on a block-by-block basis to the memory 160.

The memory 160 accumulates the reconstructed blocks output by the synthesis unit 150 as decoded images on a frame-by-frame basis. The memory 160 outputs the stored decoded images to the prediction unit 170. Note that a loop filter may be interposed between the synthesis unit 150 and the memory 160.

The prediction unit 170 performs prediction processing on a block-by-block basis to generate a prediction block corresponding to the block to be coded, and outputs the generated prediction block to the subtraction unit 110 and the synthesis unit 150. The block to be coded on which prediction processing is performed is called the block to be predicted.

The prediction unit 170 has an intra prediction unit 171, an inter prediction unit 172, and a switching unit 173. In this embodiment, the inter prediction unit 172 corresponds to a prediction device that performs prediction processing on a block-by-block basis.

The intra prediction unit 171 selects an optimal intra prediction mode to be applied to the prediction target block from among multiple intra prediction modes, and predicts the prediction target block using the selected intra prediction mode. The intra prediction unit 171 generates an intra prediction block by referring to decoded pixel values adjacent to the prediction target block in the decoded image stored in the memory 160, and outputs the generated intra prediction block to the switching unit 173. The intra prediction unit 171 also outputs information related to the selected intra prediction mode to the entropy coding unit 130.

The inter prediction unit 172 uses the decoded image stored in the memory 160 as a reference image to calculate a motion vector by a method such as block matching, predicts the block to be predicted, generates an inter prediction block, and outputs the generated inter prediction block to the switching unit 173. The inter prediction unit 172 selects an optimal inter prediction method from inter prediction using multiple reference images (typically, bi-prediction) and inter prediction using one reference image (unidirectional prediction), and performs inter prediction using the selected inter prediction method. The inter prediction unit 172 outputs information related to the inter prediction (motion vector information, etc.) to the entropy coding unit 130.

In this embodiment, the inter prediction unit 172 has a triangular partitioning prediction unit 172a that performs triangular partitioning prediction (TPM) (see FIG. 2). The triangular partitioning prediction unit 172a assigns a motion vector to each of the regions obtained by dividing the encoding target block by diagonals, and performs motion compensation prediction. When applying triangular partitioning prediction to the encoding target block, the inter prediction unit 172 outputs a triangular partitioning prediction application flag indicating that triangular partitioning prediction is applied to this encoding target block to the entropy coding unit 130, and transmits the triangular partitioning prediction application flag from the entropy coding unit 130 to the decoding side. Details of the triangular partitioning prediction unit 172a will be described later.

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

Next, we will explain the triangular decomposition prediction unit 172a according to this embodiment. Figure 2 is a diagram showing the configuration of the triangular decomposition prediction unit 172a according to this embodiment.

As shown in FIG. 2, the triangulation prediction unit 172a includes a division unit 1721, a generation unit 1722, a calculation unit 1723, a determination unit 1724, and a synthesis unit 1725.

The division unit 1721 divides the prediction target block diagonally and outputs two triangular regions to the generation unit 1722. The triangular region is an example of a prediction region in which the prediction target block is divided by straight lines. There are two types of division methods: a method shown in FIG. 3(a) and a method shown in FIG. 3(b). In the method shown in FIG. 3(a), the division unit 1721 divides the prediction target block by a division line passing through the top left nadir position and the bottom right nadir position of the coding target block. In the method shown in FIG. 3(b), the division unit 1721 divides the prediction target block by a division line passing through the top right nadir position and the bottom left nadir position of the coding target block. The division unit 1721 outputs a division direction flag indicating whether the division direction is the diagonal direction shown in FIG. 3(a) or the diagonal direction shown in FIG. 3(b) to the entropy coding unit 130, and transmits the division direction flag from the entropy coding unit 130 to the decoding side.

The generation unit 1722 generates a region prediction image for each of the two triangular regions using a motion vector, and outputs the two region prediction images to the calculation unit 1723 and the synthesis unit 1725. Specifically, the generation unit 1722 assigns a motion vector to each region obtained by dividing the prediction target block, and generates a prediction image for each region using the assigned motion vector. Here, the generation unit 1722 arranges multiple candidates to be used as reference sources for the motion vector in order of priority, and selects one motion vector for each triangular region from a certain number of top motion vectors. The generation unit 1722 outputs motion vector information indicating the selected motion vector to the entropy coding unit 130, and transmits the motion vector information from the entropy coding unit 130 to the decoding side.

The calculation unit 1723 calculates similarity information indicating the similarity between the two region prediction images generated by the generation unit 1722, and outputs the calculated similarity information to the determination unit 1724. For example, as shown in FIG. 4(a), the calculation unit 1723 calculates similarity information indicating the similarity between a boundary region R1 between region prediction image 1 and region prediction image 2, and a boundary region R2 between region prediction image 2 and region prediction image 1. The similarity information may be any information that indicates similarity, and for example, the sum of absolute differences (SAD) may be used as the similarity information.

The calculation unit 1723 may calculate the SAD between pixel values (multiple) in the boundary region R1 and the corresponding pixel values (multiple) in the boundary region R2 as similarity information. A smaller SAD indicates a higher similarity, and a larger SAD indicates a lower similarity.

Calculating the similarity information may be calculating the similarity between two reference images corresponding to the two region prediction images. The similarity between the reference images may be calculated as the SAD between pixel values (multiple) in one reference image and corresponding pixel values (multiple) in the other reference image.

The determination unit 1724 determines a synthesis method to be used for synthesizing the two regional prediction images from among a plurality of methods based on the similarity information calculated by the calculation unit 1723, and outputs information indicating the determined synthesis method to the synthesis unit 1725. For example, the plurality of methods includes a first method (hereinafter referred to as the "blending method") in which the boundary area between the two regional prediction images is mixed by weighted synthesis using a weighting coefficient for each pixel position. The determination unit 1724 determines whether or not to use the blending method as the synthesis method to be used for synthesizing the two regional prediction images based on the similarity information calculated by the calculation unit 1723. The blending method makes it possible to suppress discontinuity due to motion prediction compensation for each region.

In this embodiment, the multiple methods further include a second method (hereinafter referred to as the "non-blending method") that does not mix boundary regions by weighted synthesis. The decision unit 1724 decides whether to use the blending method or the non-blending method as the synthesis method to be used for synthesizing two region prediction images based on the similarity information calculated by the calculation unit 1723. The non-blending method makes it possible to avoid edge blurring caused by the blending method for sequences that include many flat regions and edges.

When it is possible to switch between such blending and non-blending methods, it may be necessary to transmit a flag indicating whether the blending or non-blending method is to be applied to the decoding side. However, in background areas of an image (e.g., smooth areas such as the sky), the characteristics of the predicted image generated will not change whether the blending method or the non-blending method is used, and the coding efficiency will not be affected regardless of which method is selected.

In this embodiment, the determination unit 1724 determines either the blending method or the non-blending method based on the similarity information calculated by the calculation unit 1723. Such similarity information can also be calculated on the decoding side, so a common method can be implicitly determined on the encoding side and the decoding side without transmitting a flag indicating whether the blending method or the non-blending method is to be applied to the decoding side. This makes it unnecessary to transmit (signal) such a flag to the decoding side, and can suppress an increase in the amount of flags to be signaled.

For example, as shown in Figures 4(b) and (c), based on the similarity information calculated by the calculation unit 1723, the determination unit 1724 determines the blending method when the similarity indicated by the similarity information is lower than a threshold, and determines the non-blending method when the similarity indicated by the similarity information is higher than the threshold. This threshold may be a predetermined fixed value, or may be a variable value transmitted from the encoding side to the decoding side.

The synthesis unit 1725 synthesizes the two regional prediction images output by the generation unit 1722 using the synthesis method determined by the determination unit 1724, and outputs a prediction block corresponding to the block to be predicted. In this embodiment, if the determination unit 1724 determines the blending method, the synthesis unit 1725 synthesizes the two regional prediction images using the blending method, and if the determination unit 1724 determines the non-blending method, the synthesis unit 1725 synthesizes the two regional prediction images using the non-blending method.

FIG. 5 is a diagram showing the operation of synthesizing two area prediction images P ₁ and P _2. As shown in FIG. 5(a), when the synthesis unit 1725 synthesizes two area prediction images P ₁ and P ₂ by the blending method, the synthesis unit 1725 synthesizes the two area prediction images P ₁ and P ₂ by weighted averaging using a weighting factor map (Weight map) according to the block size and block shape of the prediction target block. As a result, the boundary regions R1 and R2 shown in FIG. 4(a) are adjusted to be continuous. On the other hand, as shown in FIG. 5(b), when the synthesis unit 1725 synthesizes two area prediction images P ₁ and P ₂ by the non-blending method, the synthesis unit 1725 synthesizes the two area prediction images P ₁ and P ₂ without weighted averaging.

<Configuration of Decoding Device>
Next, the configuration of a decoding device according to this embodiment will be described, focusing mainly on the differences from the configuration of the encoding device described above. Fig. 6 is a diagram showing the configuration of a decoding device 2 according to this embodiment. The decoding device 2 is a device that decodes a current block from an encoded stream.

As shown in FIG. 6, the decoding device 2 has an entropy decoding unit 200, an inverse quantization/inverse transform unit 210, a synthesis unit 220, a memory 230, and a prediction unit 240.

The entropy decoding unit 200 decodes the coding stream generated by the coding device 1, obtains quantized transform coefficients, and outputs the obtained transform coefficients to the inverse quantization/inverse transform unit 210 (inverse quantization unit 211). The entropy decoding unit 200 also obtains various types of signaling information. For example, the entropy decoding unit 200 obtains information related to the prediction process to be applied to the block to be decoded, and outputs the obtained information to the prediction unit 240.

The inverse quantization and inverse transform unit 210 performs inverse quantization processing and inverse transform processing on a block-by-block basis. The inverse quantization and inverse transform unit 210 has an inverse quantization unit 211 and an inverse transform unit 212.

The inverse quantization unit 211 performs an inverse quantization process corresponding to the quantization process performed by the quantization unit 122 of the encoding device 1. The inverse quantization unit 211 restores the transform coefficients of the block to be decoded by inverse quantizing the quantized transform coefficients output by the entropy decoding unit 200 using a quantization parameter (Qp) and a quantization matrix, and outputs the restored transform coefficients to the inverse transform unit 212.

The inverse transform unit 212 performs inverse transform processing corresponding to the transform processing performed by the transform unit 121 of the encoding device 1. The inverse transform unit 212 performs inverse transform processing on the transform coefficients output by the inverse quantization unit 211 to restore the prediction residual, and outputs the restored prediction residual (restored prediction residual) to the synthesis unit 220.

The synthesis unit 220 reconstructs (decodes) the block to be decoded by synthesizing the prediction residual output by the inverse transform unit 212 and the prediction block output by the prediction unit 240 on a pixel-by-pixel basis, and outputs the reconstructed block to the memory 230.

The memory 230 stores the reconstructed blocks output by the synthesis unit 220 as decoded images on a frame-by-frame basis. The memory 230 outputs the decoded images on a frame-by-frame basis to the outside of the decoding device 2. Note that a loop filter may be interposed between the synthesis unit 220 and the memory 230.

The prediction unit 240 performs prediction on a block-by-block basis. The prediction unit 240 has an intra prediction unit 241, an inter prediction unit 242, and a switching unit 243.

The intra prediction unit 241 refers to reference pixels adjacent to the block to be decoded in the decoded image stored in the memory 230, and predicts the block to be decoded by intra prediction based on the information output by the entropy decoding unit 200. The intra prediction unit 241 then generates an intra prediction block and outputs the generated intra prediction block to the switching unit 243.

The inter prediction unit 242 predicts the block to be decoded by inter prediction using the decoded image stored in the memory 230 as a reference image. The inter prediction unit 242 generates an inter prediction block by performing inter prediction using the motion vector information output by the entropy decoding unit 200, and outputs the generated inter prediction block to the switching unit 243.

In this embodiment, the inter prediction unit 242 has a triangular partition prediction unit 242a that performs triangular partition prediction (TPM) (see FIG. 7). When the entropy decoding unit 200 acquires a triangular partition prediction application flag indicating that triangular partition prediction is to be applied to the block to be predicted, the inter prediction unit 242 applies triangular partition prediction to the block to be predicted. Details of the triangular partition prediction unit 242a will be described later.

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

Next, the triangular decomposition prediction unit 242a according to this embodiment will be described. FIG. 7 is a diagram showing the configuration of the triangular decomposition prediction unit 242a according to this embodiment.

As shown in FIG. 7, the triangulation prediction unit 242a includes a division unit 2421, a generation unit 2422, a calculation unit 2423, a determination unit 2424, and a synthesis unit 2425.

The division unit 2421 divides the prediction target block diagonally based on the division direction flag acquired by the entropy decoding unit 200, and outputs two triangular regions to the generation unit 2422.

The generation unit 2422 generates a region prediction image for each of the two triangular regions based on the motion vector information acquired by the entropy decoding unit 200, and outputs the two region prediction images to the calculation unit 2423 and the synthesis unit 2425.

The calculation unit 2423 calculates similarity information indicating the similarity between the two region prediction images generated by the generation unit 2422, and outputs the calculated similarity information to the determination unit 2424. The calculation method of the similarity information is the same as that on the encoding side, and the similarity information is calculated using a rule (algorithm) that is common to the encoding side and the decoding side.

The determination unit 2424 determines the synthesis method to be used for synthesizing the two area prediction images from among a plurality of methods based on the similarity information calculated by the calculation unit 2423, and outputs information indicating the determined synthesis method to the synthesis unit 2425. In this embodiment, the determination unit 2424 determines whether to use the blending method or the non-blending method as the synthesis method to be used for synthesizing the two area prediction images based on the similarity information calculated by the calculation unit 2423. The method of determining the synthesis method is the same as that on the encoding side, and the synthesis method is determined using a rule common to the encoding side and the decoding side. In other words, the determination unit 2424 determines the synthesis method based on the similarity information, without being based on a flag indicating whether the blending method or the non-blending method is to be applied.

The synthesis unit 2425 synthesizes the two regional prediction images output by the generation unit 2422 using the synthesis method determined by the determination unit 2424, and outputs a prediction block corresponding to the block to be predicted. In this embodiment, if the determination unit 2424 determines the blending method, the synthesis unit 2425 synthesizes the two regional prediction images using the blending method, and if the determination unit 2424 determines the non-blending method, the synthesis unit 2425 synthesizes the two regional prediction images using the non-blending method.

<Operation of Triangulation Prediction Unit>
Next, the operation of the triangular decomposition prediction units 172a and 242a according to this embodiment will be described. Since the triangular decomposition prediction units 172a and 242a perform similar operations, the triangular decomposition prediction unit 242a will be taken as an example for description here. Fig. 8 is a diagram showing the operation flow of the triangular decomposition prediction unit 242a according to this embodiment.

As shown in FIG. 8, in step S1, the division unit 2421 divides the prediction target block diagonally based on the division direction flag acquired by the entropy decoding unit 200, and outputs two triangular regions to the generation unit 2422.

In step S2, the generation unit 2422 generates a region prediction image for each of the two triangular regions based on the motion vector information acquired by the entropy decoding unit 200, and outputs the two region prediction images to the calculation unit 2423 and the synthesis unit 2425.

In step S3, the calculation unit 2423 calculates similarity information indicating the similarity between the two region prediction images generated by the generation unit 2422, and outputs the calculated similarity information to the determination unit 2424.

In step S4, the determination unit 2424 determines whether the blending method or the non-blending method is to be used as the synthesis method for synthesizing the two area prediction images based on the similarity information calculated by the calculation unit 2423.

In step S5, the synthesis unit 2425 synthesizes the two area prediction images output by the generation unit 2422 using the synthesis method determined by the determination unit 2424, and outputs a prediction block corresponding to the block to be predicted.

In this way, according to this embodiment, a common method can be implicitly determined on the encoding side and the decoding side without transmitting a flag indicating whether the blending method or the non-blending method is to be applied to the decoding side. This makes it unnecessary to transmit (signal) a flag indicating the blending method to the decoding side even when multiple blending methods are introduced into the triangulation prediction, and can suppress an increase in the amount of flags to be signaled.

<Other embodiments>
In the above-mentioned embodiment, an example is described in which the blending method or the non-blending method is determined as the synthesis method used for synthesizing two area prediction images based on similarity information.However, when introducing a plurality of blending methods, it is also possible to determine which of the plurality of blending methods is used based on similarity information.

The multiple blending methods may have different parameters for blending the boundary regions. Here, the parameters may be at least one of the range of the boundary region and the set of weighting coefficients. For example, a first blending method is introduced in which the range of the boundary region to which the blending process is applied is a first range (narrow range) and a first set of weighting coefficients is used, and a second blending method is introduced in which the range of the boundary region to which the blending process is applied is a second range (wide range) and a second set of weighting coefficients is used. Here, the weighting coefficients constituting the second set are greater than those of the first set.

Under such a premise, the determination units 1724 and 2424 determine the second blending method when the similarity indicated by the similarity information calculated by the calculation units 1723 and 2423 is lower than a threshold value, and determine the first blending method when the similarity indicated by this similarity information is higher than the threshold value.

Alternatively, a first threshold and a second threshold greater than the first threshold may be introduced. The decision units 1724 and 2424 decide on the non-blending method if the similarity indicated by the similarity information calculated by the calculation units 1723 and 2423 is higher than the second threshold, decide on the second blending method if the similarity indicated by this similarity information is lower than the first threshold, and decide on the first blending method if the similarity indicated by this similarity information is within the range from the first threshold to the second threshold.

In the above embodiment, an example was described in which the prediction target block was divided by a diagonal line to output two triangular regions, but the division shape is not limited to triangles and can be any shape divided by straight lines. The prediction target block can also be divided into three or more regions. In that case, the similarity near the boundary for each pair of regions in three or more prediction regions is calculated, and a weighting coefficient to be used for combining the pairs of regions is determined based on that information.

A program may be provided that causes a computer to execute each process performed by the encoding device 1. A program may be provided that causes a computer to execute each process performed by the decoding device 2. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

The circuits that execute the processes performed by the encoding device 1 may be integrated, and the encoding device 1 may be configured as a semiconductor integrated circuit (chip set, SoC). The circuits that execute the processes performed by the decoding device 2 may be integrated, and the decoding device 2 may be configured as a semiconductor integrated circuit (chip set, SoC).

The above describes the embodiment in detail with reference to the drawings, but the specific configuration is not limited to the above, and various design changes can be made without departing from the spirit of the invention.

1: Encoding device 2: Decoding device 100: Block division unit 110: Subtraction unit 120: Transformation and quantization unit 121: Transformation unit 122: Quantization unit 130: Entropy encoding unit 140: Inverse quantization and inverse transform unit 141: Inverse quantization unit 142: Inverse transform unit 150: Synthesis unit 160: Memory 170: Prediction unit 171: Intra prediction unit 172: Inter prediction unit 172a: Triangular division prediction unit 173: Switching unit 200: Entropy decoding unit 210: Inverse transformation unit 211: Inverse quantization unit 212: Inverse transformation unit 220: Synthesis unit 230: Memory 240: Prediction unit 241: Intra prediction unit 242: Inter prediction unit 242a: Triangular division prediction unit 243: Switching unit 1721: Division unit 1722 : Generation unit 1723 : Calculation unit 1724 : Determination unit 1725 : Combination unit 2421 : Division unit 2422 : Generation unit 2423 : Calculation unit 2424 : Determination unit 2425 : Combination unit

Claims (4)

A prediction device that performs prediction on a block basis by dividing an image,
a division unit that divides a block to be predicted by straight lines and outputs a plurality of prediction regions;
a generation unit that generates a plurality of regional predicted images corresponding to the plurality of prediction regions;
a determining unit that determines a synthesis method to be used for synthesizing the plurality of regional predicted images from among a plurality of methods;
a synthesis unit that synthesizes the plurality of regional predicted images using the synthesis method determined by the determination unit, and outputs a predicted block corresponding to the block to be predicted. An encoding device comprising the prediction device according to claim 1. A decoding device comprising the prediction device according to claim 1. A program that causes a computer to function as the prediction device according to claim 1.

Images