Decoding device, and bit stream generation device

Abstract

To provide an encoding device capable of achieving further improvements.SOLUTION: A decoding device 200 is a decoding device that decodes an image block, which includes a circuit and a memory. The circuit acquires a quantization primary coefficient or a quantization secondary coefficient of the image block from the bit stream using the memory and determines whether to apply the inverse quadratic transformation to the image block. (i)When the inverse quadratic transformation is not applied, first inverse quantization is performed on the primary coefficient to calculate the primary coefficient. (ii) When applying the inverse quadratic transformation, the quantization secondary coefficient is calculated by performing a second inverse quantization different from the first inverse quantization on the quantization secondary coefficient, and an inverse quadratic transformation is performed from quadratic coefficients to primary coefficients, and an inverse secondary transform from primary coefficient to the residuals of the image block.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present disclosure relates to an encoding device that encodes an image block. [Background technology]

[0002] A video coding standard called HEVC (High-Efficiency Video Coding) has been standardized by the Joint Collaborative Team on Video Coding (JCT-VC). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] H.265(ISO / IEC 23008-2 HEVC(High Efficiency Video Coding)) Summary of the Invention [Problem to be solved by the invention]

[0004] Further improvements in such encoding and decoding techniques are required.

[0005] Therefore, an object of the present disclosure is to provide an encoding device and the like that can achieve further improvements. [Means for solving the problem]

[0006] A decoding device according to one aspect of the present disclosure is a decoding device for decoding an image block, comprising a circuit and a memory, wherein the circuit uses the memory to obtain quantized primary coefficients or quantized secondary coefficients of the image block from a bitstream, determine whether to apply an inverse secondary transform to the image block, (i) if the inverse secondary transform is not to be applied, calculate primary coefficients by performing a first inverse quantization on the quantized primary coefficients, and (ii) if the inverse secondary transform is to be applied, calculate secondary coefficients by performing a second inverse quantization different from the first inverse quantization on the quantized secondary coefficients, perform an inverse secondary transform from the secondary coefficients to primary coefficients, and perform an inverse primary transform from the primary coefficients to residuals of the image block.

[0007] These general or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0008] The present disclosure can provide an encoding device and the like that can achieve further improvements. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a functional configuration of a coding device according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of block division according to the first embodiment. [Figure 3] FIG. 3 is a table showing the transformation basis functions corresponding to each transformation type. [Figure 4A] FIG. 4A is a diagram showing an example of the shape of a filter used in ALF. [Figure 4B] FIG. 4B is a diagram showing another example of the shape of the filter used in ALF. [Figure 4C]FIG. 4C is a diagram showing another example of the shape of the filter used in ALF. [Figure 5A] FIG. 5A is a diagram showing 67 intra prediction modes in intra prediction. [Figure 5B] FIG. 5B is a flowchart for explaining an outline of the predicted image correction process using the OBMC process. [Figure 5C] FIG. 5C is a conceptual diagram for explaining an outline of the predicted image correction process using the OBMC process. [Figure 5D] FIG. 5D is a diagram showing an example of FRUC. [Figure 6] FIG. 6 is a diagram for explaining pattern matching (bilateral matching) between two blocks along a motion trajectory. [Figure 7] FIG. 7 is a diagram for explaining pattern matching (template matching) between a template in a current picture and a block in a reference picture. [Figure 8] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. [Figure 9A] FIG. 9A is a diagram for explaining derivation of a motion vector for each sub-block based on motion vectors of a plurality of adjacent blocks. [Figure 9B] FIG. 9B is a diagram for explaining an outline of the motion vector derivation process in the merge mode. [Figure 9C] FIG. 9C is a conceptual diagram for explaining an outline of the DMVR process. [Figure 9D] FIG. 9D is a diagram for explaining an outline of a predicted image generation method using luminance correction processing by LIC processing. [Figure 10] FIG. 10 is a block diagram showing a functional configuration of a decoding device according to the first embodiment. [Figure 11] FIG. 11 is a flowchart showing an example of the transform process, the quantization process, and the encoding process according to the first embodiment. [Figure 12]FIG. 12 shows an example of the positions of quantization matrices in a coded bitstream according to the first embodiment. [Figure 13] FIG. 13 is a flowchart showing an example of the decoding process, the inverse quantization process, and the inverse transform process according to the first embodiment. [Figure 14] FIG. 14 is a flowchart showing an example of the transform process, the quantization process, and the encoding process according to the second embodiment. [Figure 15] FIG. 15 is a flowchart showing an example of the decoding process, the inverse quantization process, and the inverse transform process according to the second embodiment. [Figure 16] FIG. 16 is a flowchart showing an example of a process of deriving a second quantization matrix in a modification of the second embodiment. [Figure 17] FIG. 17 is a flowchart showing an example of the transform process, the quantization process, and the encoding process according to the third embodiment. [Figure 18] FIG. 18 is a flowchart showing an example of the decoding process, the inverse quantization process, and the inverse transform process according to the third embodiment. [Figure 19] FIG. 19 is a flowchart showing an example of the transform process, the quantization process, and the encoding process according to the fourth embodiment. [Figure 20] FIG. 20 is a diagram illustrating an example of the secondary transformation according to the fourth embodiment. [Figure 21] FIG. 21 is a flowchart showing an example of the decoding process, the inverse quantization process, and the inverse transform process according to the fourth embodiment. [Figure 22] FIG. 22 is a diagram illustrating an example of the inverse secondary transformation according to the fourth embodiment. [Figure 23] FIG. 23 is a flowchart showing an example of the transform process, the quantization process, and the encoding process according to the fifth embodiment. [Figure 24] FIG. 24 is a flowchart showing an example of the decoding process, the inverse quantization process, and the inverse transform process according to the fifth embodiment. [Figure 25] FIG. 25 is a diagram showing the overall configuration of a content supply system that realizes a content distribution service. [Figure 26] FIG. 26 is a diagram showing an example of a coding structure for scalable coding. [Figure 27] FIG. 27 is a diagram showing an example of a coding structure for scalable coding. [Figure 28] FIG. 28 is a diagram showing an example of a display screen of a web page. [Figure 29] FIG. 29 is a diagram showing an example of a display screen of a web page. [Figure 30] FIG. 30 is a diagram illustrating an example of a smartphone. [Figure 31] FIG. 31 is a block diagram showing an example of the configuration of a smartphone. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that formed the basis of this disclosure) In the next generation of video compression standards, a secondary transform of the coefficients obtained by the primary transform of the residual is being considered to further remove spatial redundancy. Even when such a secondary transform is performed, it is expected that the coding efficiency will be improved while suppressing the degradation of subjective image quality.

[0011] Therefore, an encoding device according to one aspect of the present disclosure is an encoding device that encodes a block of an image to be encoded, and includes a circuit and a memory. The circuit uses the memory to perform a primary transformation from the residual of the block to be encoded to a primary coefficient, and determines whether to apply a secondary transformation to the block to be encoded. (i) If the secondary transformation is not to be applied, the circuit calculates quantized primary coefficients by performing a first quantization on the primary coefficients, and (ii) If the secondary transformation is to be applied, the circuit performs a secondary transformation from the primary coefficients to secondary coefficients and calculates quantized secondary coefficients by performing a second quantization on the secondary coefficients that is different from the first quantization, and generates an encoded bitstream by encoding the quantized primary coefficients or the quantized secondary coefficients.

[0012] This allows different quantization to be performed depending on whether or not a secondary transform is applied to the block to be coded. Secondary coefficients obtained by secondary transforming primary coefficients expressed in a first space are expressed in a secondary space, not a primary space. Therefore, even if quantization for primary coefficients is applied to secondary coefficients, it is difficult to improve coding efficiency while suppressing degradation of subjective image quality. For example, quantization for reducing loss of low-frequency components to suppress degradation of subjective image quality and increasing loss of high-frequency components to improve coding efficiency differs between primary space and secondary space. Therefore, by performing different quantization depending on whether or not a secondary transform is applied to the block to be coded, coding efficiency can be improved while suppressing degradation of subjective image quality, compared to when a common quantization is used.

[0013] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the first quantization may be weighted quantization using a first quantization matrix, and the second quantization may be weighted quantization using a second quantization matrix different from the first quantization matrix.

[0014] According to this, weighted quantization using a first quantization matrix can be performed as the first quantization. Furthermore, weighted quantization using a second quantization matrix different from the first quantization matrix can be performed as the second quantization. Therefore, the first quantization matrix corresponding to the primary space can be used for quantization of the primary coefficients, and the second quantization matrix corresponding to the secondary space can be used for quantization of the secondary coefficients. Therefore, it is possible to improve coding efficiency while suppressing degradation of subjective image quality, both when a secondary transform is applied and when it is not applied.

[0015] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the circuit may further write the first quantization matrix and the second quantization matrix to the encoded bitstream.

[0016] This allows the first and second quantization matrices to be included in the coded bitstream, which makes it possible to adaptively determine the first and second quantization matrices depending on the original image, thereby improving coding efficiency while suppressing degradation of subjective image quality.

[0017] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the primary coefficients may include one or more first primary coefficients and one or more second primary coefficients, the secondary transform may be applied to the one or more first primary coefficients and not to the one or more second primary coefficients, the second quantization matrix may include one or more first component values corresponding to the one or more first primary coefficients and one or more second component values corresponding to the one or more second primary coefficients, each of the one or more second component values of the second quantization matrix may match a corresponding component value of the first quantization matrix, and when writing the second quantization matrix, only the one or more first component values of the one or more first component values and the one or more second component values may be written to the encoded bitstream.

[0018] This allows each of the one or more second component values of the second quantization matrix to match the corresponding component value of the first quantization matrix, thereby eliminating the need to write the one or more second component values of the second quantization matrix into the encoded bitstream, thereby improving encoding efficiency.

[0019] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the secondary transformation may selectively use a plurality of predetermined bases, the encoded bitstream may include a plurality of second quantization matrices corresponding to the plurality of bases, and the second quantization may select a second quantization matrix corresponding to the base used in the secondary transformation from among the plurality of second quantization matrices.

[0020] According to this, second quantization can be performed using a second quantization matrix corresponding to the basis used in the secondary transformation. The characteristics of the secondary space expressing the secondary coefficients differ depending on the basis used in the secondary transformation. Therefore, by performing second quantization using a second quantization matrix corresponding to the basis used in the secondary transformation, second quantization can be performed using a quantization matrix that is more suited to the secondary space, thereby improving coding efficiency while suppressing degradation of subjective image quality.

[0021] In addition, in the encoding device according to one aspect of the present disclosure, for example, the first quantization matrix and the second quantization matrix may be predefined in a standard.

[0022] According to this, the first quantization matrix and the second quantization matrix are defined in advance in the standard specification, so that the first quantization matrix and the second quantization matrix do not need to be included in the coded bitstream, and the amount of code for the first quantization matrix and the second quantization matrix can be reduced.

[0023] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the circuit may further derive the second quantization matrix from the first quantization matrix.

[0024] This allows the second quantization matrix to be derived from the first quantization matrix, thereby eliminating the need to transmit the second quantization matrix to the decoding device, thereby improving coding efficiency.

[0025] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the primary coefficients may include one or more first primary coefficients and one or more second primary coefficients, the secondary transform may be applied to the one or more first primary coefficients and not to the one or more second primary coefficients, the second quantization matrix may include one or more first component values corresponding to the one or more first primary coefficients and one or more second component values corresponding to the one or more second primary coefficients, each of the one or more second component values of the second quantization matrix may match a corresponding component value of the first quantization matrix, and in deriving the second quantization matrix, the one or more first component values of the second quantization matrix may be derived from the first quantization matrix.

[0026] This allows each of the one or more second component values of the second quantization matrix to match the corresponding component value of the first quantization matrix, thereby eliminating the need to derive the one or more second component values of the second quantization matrix from the first quantization matrix, thereby reducing the processing load.

[0027] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the second quantization matrix may be derived by applying the secondary transformation to the first quantization matrix.

[0028] This allows the second quantization matrix to be derived by applying a secondary transformation to the first quantization matrix, thereby converting the first quantization matrix corresponding to the primary space into the second quantization matrix corresponding to the secondary space, thereby improving coding efficiency while suppressing degradation of subjective image quality.

[0029] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the circuit may further derive a third quantization matrix from the first quantization matrix, with each component value of the third quantization matrix being larger the smaller the corresponding component value of the first quantization matrix, derive a fourth quantization matrix by applying the secondary transformation to the third quantization matrix, and derive a fifth quantization matrix from the fourth quantization matrix as the second quantization matrix, with each component value of the fifth quantization matrix being larger the smaller the corresponding component value of the fourth quantization matrix.

[0030] This reduces the impact of rounding errors during secondary transformation on components with relatively small values included in the first quantization matrix. That is, it reduces the impact of rounding errors on the values of components applied to coefficients for which loss is desired to be minimized in order to suppress degradation of subjective image quality. Therefore, it is possible to further suppress degradation of subjective image quality.

[0031] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, each component value of the third quantization matrix may be the reciprocal of the corresponding component value of the first quantization matrix, and each component value of the fifth quantization matrix may be the reciprocal of the corresponding component value of the fourth quantization matrix.

[0032] This allows the reciprocal of the corresponding component value of the first quantization matrix / fourth quantization matrix to be used as each component value of the third quantization matrix / fifth quantization matrix, thereby deriving the component value with simple calculations and reducing the processing load or processing time required to derive the second quantization matrix.

[0033] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the first quantization may be weighted quantization using a quantization matrix, and the second quantization may be unweighted quantization not using a quantization matrix.

[0034] This allows for unweighted quantization, which does not use a quantization matrix, to be used as the second quantization, thereby preventing degradation of subjective image quality due to the use of the first quantization matrix for the first quantization for the second quantization, and omitting the code amount or derivation process of the quantization matrix for the second quantization.

[0035] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, the first quantization may be weighted quantization using a first quantization matrix, and the secondary transformation may involve (i) calculating weighted primary coefficients by multiplying each of the primary coefficients by a corresponding component value of a weight matrix, and (ii) converting the weighted primary coefficients into secondary coefficients, and the second quantization may involve dividing each of the secondary coefficients by a quantization step common to the secondary coefficients.

[0036] This allows weighted primary coefficients to be calculated by multiplying each primary coefficient by a corresponding component value of the weighting matrix. Quantization weighting can be applied to the primary coefficients before secondary transformation. Therefore, when secondary transformation is applied, quantization equivalent to weighted quantization can be performed without preparing a new quantization matrix corresponding to the secondary space. As a result, it is possible to improve coding efficiency while suppressing degradation of subjective image quality.

[0037] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the circuit may further derive the weight matrix from the first quantization matrix.

[0038] This allows the weight matrix to be derived from the first quantization matrix, thereby reducing the amount of code required for the weight matrix and improving coding efficiency while suppressing degradation of subjective image quality.

[0039] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the circuit may further derive the common quantization step from a quantization parameter for the current block to be encoded.

[0040] This allows a quantization step common to the secondary coefficients of the block to be coded to be derived from the quantization parameter. Therefore, new information for the common quantization step does not need to be included in the coded stream, and the amount of code for the common quantization step can be reduced.

[0041] An encoding method according to one aspect of the present disclosure is an encoding method for encoding a block of an image to be encoded, which performs a primary transformation from a residual of the block to be encoded to a primary coefficient, determines whether to apply a secondary transformation to the block to be encoded, (i) if the secondary transformation is not to be applied, calculates quantized primary coefficients by performing a first quantization on the primary coefficients, and (ii) if the secondary transformation is to be applied, performs a secondary transformation from the primary coefficients to secondary coefficients and calculates quantized secondary coefficients by performing a second quantization different from the first quantization on the secondary coefficients, and generates an encoded bitstream by encoding the quantized primary coefficients or the quantized secondary coefficients.

[0042] This makes it possible to achieve the same effect as the encoding device described above.

[0043] An encoding device according to one aspect of the present disclosure is an encoding device that encodes a block of an image to be encoded, and includes a circuit and a memory. The circuit uses the memory to perform a primary transform of a residual of the block to be encoded into a primary coefficient, and determines whether to apply a secondary transform to the block to be encoded. (i) If the secondary transform is not to be applied, the circuit calculates a first quantized primary coefficient by performing a first quantization on the primary coefficient, and (ii) If the secondary transform is to be applied, the circuit calculates a second quantized primary coefficient by performing a second quantization on the primary coefficient, and performs a secondary transform from the second quantized primary coefficient to a quantized secondary coefficient. The circuit generates an encoded bitstream by encoding the first quantized primary coefficient or the quantized secondary coefficient.

[0044] This allows quantization to be performed before secondary transformation, so if the secondary transformation process is lossless, the secondary transformation can be removed from the prediction process loop. This reduces the load on the processing pipeline. Furthermore, by performing quantization before secondary transformation, it is not necessary to separate the first quantization matrix and the second quantization matrix, which simplifies the process.

[0045] An encoding method according to one aspect of the present disclosure is an encoding method for encoding a block of an image to be encoded, which comprises: first-order transforming a residual of the block to be encoded into a first-order coefficient; determining whether to apply a second-order transform to the block to be encoded; (i) if the second-order transform is not to be applied, calculating a first quantized first-order coefficient by performing a first quantization on the first coefficient; (ii) if the second-order transform is to be applied, calculating a second quantized first-order coefficient by performing a second quantization on the first coefficient; performing a second-order transform from the second quantized first-order coefficient to a quantized second-order coefficient; and generating an encoded bitstream by encoding the first quantized first-order coefficient or the quantized second-order coefficient.

[0046] This makes it possible to achieve the same effect as the encoding device described above.

[0047] A decoding device according to one aspect of the present disclosure is a decoding device that decodes a block of an image to be decoded, and includes a circuit and a memory. The circuit uses the memory to decode quantized coefficients of the block to be decoded from an encoded bitstream, determine whether to apply an inverse secondary transform to the block to be decoded, and if the inverse secondary transform is not to be applied, calculate primary coefficients by performing a first inverse quantization on the quantized coefficients, and perform an inverse primary transform from the primary coefficients to residuals of the block to be decoded. If the inverse secondary transform is to be applied, calculate secondary coefficients by performing a second inverse quantization different from the first inverse quantization on the quantized coefficients, and perform an inverse secondary transform from the secondary coefficients to primary coefficients, and perform an inverse primary transform from the primary coefficients to residuals of the block to be decoded.

[0048] This allows different inverse quantization to be performed depending on whether or not an inverse secondary transform is applied to the block to be decoded. Secondary coefficients obtained by secondary transforming primary coefficients expressed in a first space are expressed in a secondary space, not a primary space. Therefore, even if inverse quantization for primary coefficients is applied to secondary coefficients, it is difficult to improve coding efficiency while suppressing degradation of subjective image quality. For example, quantization for reducing loss of low-frequency components to suppress degradation of subjective image quality and increasing loss of high-frequency components to improve coding efficiency differs between primary space and secondary space. Therefore, by performing different inverse quantization depending on whether or not an inverse secondary transform is applied to the block to be decoded, coding efficiency can be improved while suppressing degradation of subjective image quality, compared to when a common inverse quantization is performed.

[0049] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the first inverse quantization may be weighted inverse quantization using a first quantization matrix, and the second inverse quantization may be weighted inverse quantization using a second quantization matrix different from the first quantization matrix.

[0050] According to this, weighted inverse quantization using a first quantization matrix can be performed as the first inverse quantization. Furthermore, weighted inverse quantization using a second quantization matrix different from the first quantization matrix can be performed as the second inverse quantization. Therefore, the first quantization matrix corresponding to the primary space can be used for inverse quantization of the primary coefficients, and the second quantization matrix corresponding to the secondary space can be used for inverse quantization of the secondary coefficients. Therefore, it is possible to improve coding efficiency while suppressing degradation of subjective image quality, whether or not the inverse secondary transform is applied.

[0051] Furthermore, in the decoding device according to one aspect of the present disclosure, for example, the circuit may further decipher the first quantization matrix and the second quantization matrix from the encoded bitstream.

[0052] This allows the first and second quantization matrices to be included in the coded bitstream, which makes it possible to adaptively determine the first and second quantization matrices depending on the original image, thereby improving coding efficiency while suppressing degradation of subjective image quality.

[0053] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the secondary coefficients include one or more first secondary coefficients and one or more second secondary coefficients, the inverse secondary transform is applied to the one or more first secondary coefficients and is not applied to the one or more second secondary coefficients, the second quantization matrix includes one or more first component values corresponding to the one or more first secondary coefficients and one or more second component values corresponding to the one or more second secondary coefficients, each of the one or more second component values of the second quantization matrix matches a corresponding component value of the first quantization matrix, and when interpreting the second quantization matrix, only the one or more first component positions of the one or more first component values and the one or more second component values may be interpreted from the encoded bitstream.

[0054] This allows each of the one or more second component values of the second quantization matrix to match the corresponding component value of the first quantization matrix, eliminating the need to interpret the one or more second component values of the second quantization matrix from the coded bitstream, thereby improving coding efficiency.

[0055] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the inverse secondary transform may selectively use a plurality of predetermined bases, the encoded bitstream may include a plurality of second quantization matrices corresponding to the plurality of bases, and the second inverse quantization may select a second quantization matrix corresponding to the base used in the inverse secondary transform from among the plurality of second quantization matrices.

[0056] According to this, the characteristics of the secondary space expressing the secondary coefficients differ depending on the basis used in the inverse secondary transform. Therefore, by performing the second inverse quantization using a second quantization matrix corresponding to the basis used in the inverse secondary transform, it is possible to perform the second inverse quantization using a quantization matrix that is more suited to the secondary space, thereby improving coding efficiency while suppressing degradation of subjective image quality.

[0057] In addition, in the decoding device according to one aspect of the present disclosure, for example, the first quantization matrix and the second quantization matrix may be predefined in a standard.

[0058] According to this, the first quantization matrix and the second quantization matrix are defined in advance in the standard specification, so that the first quantization matrix and the second quantization matrix do not need to be included in the coded bitstream, and the amount of code for the first quantization matrix and the second quantization matrix can be reduced.

[0059] Furthermore, in the decoding device according to one aspect of the present disclosure, for example, the circuit may further derive the second quantization matrix from the first quantization matrix.

[0060] This allows the second quantization matrix to be derived from the first quantization matrix, eliminating the need to receive the second quantization matrix from the encoding device, thereby improving encoding efficiency.

[0061] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the secondary coefficients may include one or more first secondary coefficients and one or more second secondary coefficients, the inverse secondary transform may be applied to the one or more first secondary coefficients and not to the one or more second secondary coefficients, the second quantization matrix may include one or more first component values corresponding to the one or more first secondary coefficients and one or more second component values corresponding to the one or more second secondary coefficients, each of the one or more second component values of the second quantization matrix may match a corresponding component value of the first quantization matrix, and in deriving the second quantization matrix, the one or more first component positions may be derived from the first quantization matrix.

[0062] This allows each of the one or more second component values of the second quantization matrix to match the corresponding component value of the first quantization matrix, thereby eliminating the need to derive the one or more second component values of the second quantization matrix from the first quantization matrix, thereby reducing the processing load.

[0063] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the second quantization matrix may be derived by applying a quadratic transformation to the first quantization matrix.

[0064] This allows the second quantization matrix to be derived by applying a secondary transformation to the first quantization matrix, thereby converting the first quantization matrix corresponding to the primary space into the second quantization matrix corresponding to the secondary space, thereby improving coding efficiency while suppressing degradation of subjective image quality.

[0065] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the circuit may further derive a third quantization matrix from the first quantization matrix, with each component value of the third quantization matrix being larger the smaller the corresponding component value of the first quantization matrix; derive a fourth quantization matrix by applying a quadratic transformation to the third quantization matrix; derive a fifth quantization matrix from the fourth quantization matrix as the second quantization matrix, with each component value of the fifth quantization matrix being larger the smaller the corresponding component value of the fourth quantization matrix.

[0066] This reduces the impact of rounding errors during secondary transformation on components with relatively small values included in the first quantization matrix. That is, it reduces the impact of rounding errors on the values of components applied to coefficients for which loss is desired to be minimized in order to suppress degradation of subjective image quality. Therefore, it is possible to further suppress degradation of subjective image quality.

[0067] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, each component value of the third quantization matrix may be the reciprocal of the corresponding component value of the first quantization matrix, and each component value of the fifth quantization matrix may be the reciprocal of the corresponding component value of the fourth quantization matrix.

[0068] This allows the reciprocal of the corresponding component value of the first quantization matrix / fourth quantization matrix to be used as each component value of the third quantization matrix / fifth quantization matrix, thereby deriving the component value with simple calculations and reducing the processing load or processing time required to derive the second quantization matrix.

[0069] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the first inverse quantization may be weighted inverse quantization using a quantization matrix, and the second inverse quantization may be unweighted inverse quantization not using a quantization matrix.

[0070] This allows for unweighted inverse quantization that does not use a quantization matrix to be used as the second inverse quantization, thereby preventing degradation of subjective image quality that would otherwise occur if the first quantization matrix for the first inverse quantization were used for the second inverse quantization, and omitting the process of encoding or deriving a quantization matrix for the second quantization.

[0071] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, the first inverse quantization may be weighted inverse quantization using a first quantization matrix, the second inverse quantization may calculate the secondary coefficients by multiplying each of the quantized coefficients by a quantization step that is common to the quantized coefficients, and the inverse secondary transform may calculate the primary coefficients by (i) inversely transforming the secondary coefficients into weighted primary coefficients, and (ii) dividing each of the weighted primary coefficients by a corresponding component value of a weight matrix.

[0072] This allows the primary coefficients to be calculated by dividing each weighted primary coefficient by the corresponding component value of the weight matrix. In other words, weighting for quantization can be applied to the primary coefficients before secondary transformation. Therefore, when an inverse secondary transformation is applied, inverse quantization equivalent to weighted inverse quantization can be performed without preparing a new quantization matrix corresponding to the secondary space. As a result, it is possible to improve coding efficiency while suppressing degradation of subjective image quality.

[0073] Furthermore, in the decoding device according to one aspect of the present disclosure, for example, the circuit may further derive the weight matrix from the first quantization matrix.

[0074] This allows the weight matrix to be derived from the first quantization matrix, thereby reducing the amount of code required for the weight matrix and improving coding efficiency while suppressing degradation of subjective image quality.

[0075] Furthermore, in the decoding device according to one aspect of the present disclosure, for example, the circuit may further derive the common quantization step from a quantization parameter for the block to be decoded.

[0076] This allows a quantization step common to the secondary coefficients of the block to be decoded to be derived from the quantization parameter. Therefore, it is not necessary to include new information for the common quantization step in the coded stream, and the amount of code for the common quantization step can be reduced.

[0077] A decoding method according to one aspect of the present disclosure is a decoding method for decoding a block of an image to be decoded, which includes decoding quantized coefficients of the block to be decoded from an encoded bitstream, determining whether to apply an inverse secondary transform to the block to be decoded, and if the inverse secondary transform is not to be applied, calculating primary coefficients by performing a first inverse quantization on the quantized coefficients, and performing an inverse primary transform from the primary coefficients to residuals of the block to be decoded, and if the inverse secondary transform is to be applied, calculating secondary coefficients by performing a second inverse quantization different from the first inverse quantization on the quantized coefficients, performing an inverse secondary transform from the secondary coefficients to primary coefficients, and performing an inverse primary transform from the primary coefficients to residuals of the block to be decoded.

[0078] This makes it possible to achieve the same effect as the above-mentioned decoding device.

[0079] A decoding device according to one aspect of the present disclosure is a decoding device that decodes a block of an image to be decoded, and includes a circuit and a memory. The circuit uses the memory to decode quantized coefficients of the block to be decoded from an encoded bitstream, determine whether to apply an inverse secondary transform to the block to be decoded, and if the inverse secondary transform is not to be applied, calculate primary coefficients by performing a first inverse quantization on the quantized coefficients, and perform an inverse primary transform from the primary coefficients to residuals of the block to be decoded. If the inverse secondary transform is to be applied, perform an inverse secondary transform from the quantized coefficients to quantized primary coefficients, calculate primary coefficients by performing a second inverse quantization on the quantized primary coefficients, and perform an inverse primary transform from the primary coefficients to residuals of the block to be decoded.

[0080] According to this, in the encoding device, quantization can be performed before secondary transformation, so if the secondary transformation process is lossless, the secondary transformation can be removed from the prediction processing loop. Therefore, the load on the processing pipeline can be reduced. Furthermore, by performing quantization before secondary transformation, it is not necessary to separate the first quantization matrix and the second quantization matrix, which also simplifies the processing.

[0081] A decoding method according to one aspect of the present disclosure is a decoding method for decoding a block of an image to be decoded, which includes decoding quantized coefficients of the block to be decoded from an encoded bitstream, determining whether to apply an inverse secondary transform to the block to be decoded, and if the inverse secondary transform is not to be applied, calculating primary coefficients by performing a first inverse quantization on the quantized coefficients, and performing an inverse primary transform from the primary coefficients to residuals of the block to be decoded, and if the inverse secondary transform is to be applied, performing an inverse secondary transform from the quantized coefficients to quantized primary coefficients, calculating primary coefficients by performing a second inverse quantization on the quantized primary coefficients, and performing an inverse primary transform from the primary coefficients to residuals of the block to be decoded.

[0082] This makes it possible to achieve the same effect as the above-mentioned decoding device.

[0083] These general or specific aspects may be realized as a system, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0084] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0085] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components.

[0086] (Embodiment 1) First, an overview of the first embodiment will be described as an example of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure can be applied. However, the first embodiment is merely an example of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure can be applied, and the processes and / or configurations described in each aspect of the present disclosure can also be implemented in encoding devices and decoding devices different from the first embodiment.

[0087] When applying the processing and / or configurations described in each aspect of the present disclosure to the first embodiment, for example, any of the following may be performed.

[0088] (1) For the encoding device or decoding device of the first embodiment, among the multiple components constituting the encoding device or decoding device, components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure. (2) Any modification, such as addition, replacement, or deletion, of the functions or processes performed by some of the components constituting the encoding device or decoding device of the first embodiment may be made to the encoding device or decoding device, and then components corresponding to the components described in each aspect of the present disclosure may be replaced with the components described in each aspect of the present disclosure. (3) The method implemented by the encoding device or decoding device of the first embodiment may be modified by adding a process and / or replacing or deleting some of the processes included in the method, and then replacing the process described in each aspect of the present disclosure with the process described in each aspect of the present disclosure. (4) Some of the components constituting the encoding device or decoding device of the first embodiment may be implemented in combination with components described in each aspect of the present disclosure, components having some of the functions of the components described in each aspect of the present disclosure, or components performing some of the processing performed by the components described in each aspect of the present disclosure. (5) A component having some of the functions of some of the components constituting the encoding device or decoding device of the first embodiment, or a component that performs some of the processing performed by some of the components constituting the encoding device or decoding device of the first embodiment, is implemented in combination with a component described in each aspect of the present disclosure, a component having some of the functions of the components described in each aspect of the present disclosure, or a component that performs some of the processing performed by the components described in each aspect of the present disclosure. (6) In the method implemented by the encoding device or decoding device of the first embodiment, among the multiple processes included in the method, processes corresponding to the processes described in each aspect of the present disclosure are replaced with the processes described in each aspect of the present disclosure. (7) Some of the processes included in the method implemented by the encoding device or decoding device of the first embodiment may be implemented in combination with the processes described in each aspect of the present disclosure.

[0089] It should be noted that the manner of implementing the processes and / or configurations described in each aspect of the present disclosure is not limited to the above examples. For example, they may be implemented in a device used for a purpose different from the video / image encoding device or video / image decoding device disclosed in Embodiment 1, or the processes and / or configurations described in each aspect may be implemented independently. Furthermore, the processes and / or configurations described in different aspects may be implemented in combination.

[0090] [Outline of the encoding device] First, an overview of a coding device according to Embodiment 1 will be described. Fig. 1 is a block diagram showing a functional configuration of a coding device 100 according to Embodiment 1. The coding device 100 is a video / image coding device that codes a video / image on a block-by-block basis.

[0091] As shown in FIG. 1, the encoding device 100 is a device that encodes an image on a block-by-block basis, and includes a division unit 102, a subtraction unit 104, a transformation unit 106, a quantization unit 108, an entropy encoding unit 110, an inverse quantization unit 112, an inverse transformation unit 114, an addition unit 116, a block memory 118, a loop filter unit 120, a frame memory 122, an intra prediction unit 124, an inter prediction unit 126, and a prediction control unit 128.

[0092] The encoding device 100 is realized by, for example, a general-purpose processor and memory. In this case, when a software program stored in the memory is executed by the processor, the processor functions as the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128. Alternatively, the encoding device 100 may be realized as one or more dedicated electronic circuits corresponding to the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0093] Each component included in the encoding device 100 will be described below.

[0094] [Divided part] The division unit 102 divides each picture included in the input video into a plurality of blocks and outputs each block to the subtraction unit 104. For example, the division unit 102 first divides a picture into blocks of a fixed size (e.g., 128x128). These fixed-size blocks are sometimes called coding tree units (CTUs). The division unit 102 then divides each of the fixed-size blocks into blocks of a variable size (e.g., 64x64 or less) based on recursive quadtree and / or binary tree block division. These variable-size blocks are sometimes called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in this embodiment, there is no need to distinguish between CUs, PUs, and TUs, and some or all of the blocks in a picture may serve as the processing units of CUs, PUs, and TUs.

[0095] Fig. 2 is a diagram showing an example of block division according to embodiment 1. In Fig. 2, solid lines represent block boundaries based on quadtree block division, and dashed lines represent block boundaries based on binary tree block division.

[0096] Here, the block 10 is a square block of 128x128 pixels (128x128 block). This 128x128 block 10 is first divided into four square 64x64 blocks (quadtree block division).

[0097] The top-left 64x64 block is further divided vertically into two rectangular 32x64 blocks, and the left 32x64 block is further divided vertically into two rectangular 16x64 blocks (binary tree block division). As a result, the top-left 64x64 block is divided into two 16x64 blocks 11 and 12 and a 32x64 block 13.

[0098] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14 and 15 (binary tree block division).

[0099] The lower-left 64x64 block is divided into four square 32x32 blocks (quadtree block decomposition). Of the four 32x32 blocks, the upper-left and lower-right blocks are further divided. The upper-left 32x32 block is divided vertically into two rectangular 16x32 blocks, and the right 16x32 block is further divided horizontally into two 16x16 blocks (binary tree block decomposition). The lower-right 32x32 block is divided horizontally into two 32x16 blocks (binary tree block decomposition). As a result, the lower-left 64x64 block is divided into 16x32 block 16, two 16x16 blocks 17 and 18, two 32x32 blocks 19 and 20, and two 32x16 blocks 21 and 22.

[0100] The bottom right 64x64 block 23 is not split.

[0101] 2, block 10 is divided into 13 variable-sized blocks 11 to 23 based on recursive quad-tree and binary tree block division. This type of division is sometimes called QTBT (quad-tree plus binary tree) division.

[0102] In Fig. 2, one block is divided into four or two blocks (quadtree or binary tree block division), but the division is not limited to this. For example, one block may be divided into three blocks (ternary tree block division). Division including such ternary tree block division is sometimes called MBT (multi type tree) division.

[0103] [Subtraction section] The subtraction unit 104 subtracts a prediction signal (prediction sample) from an original signal (original sample) for each block divided by the division unit 102. That is, the subtraction unit 104 calculates a prediction error (also referred to as a residual) of a block to be coded (hereinafter referred to as a current block). Then, the subtraction unit 104 outputs the calculated prediction error to the conversion unit 106.

[0104] The original signal is an input signal to the encoding device 100, and is a signal representing an image of each picture constituting a moving image (for example, a luminance (luma) signal and two color difference (chroma) signals). Hereinafter, the signal representing an image may also be referred to as a sample.

[0105] [Conversion section] The transform unit 106 transforms the spatial domain prediction errors into frequency domain transform coefficients and outputs the transform coefficients to the quantization unit 108. Specifically, the transform unit 106 performs, for example, a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the spatial domain prediction errors.

[0106] The transform unit 106 may adaptively select a transform type from among a plurality of transform types and transform the prediction errors into transform coefficients using a transform basis function corresponding to the selected transform type. Such a transform is sometimes called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0107] The multiple transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. Fig. 3 is a table showing transform basis functions corresponding to each transform type. In Fig. 3, N represents the number of input pixels. Selection of a transform type from among these multiple transform types may depend, for example, on the type of prediction (intra prediction or inter prediction) or the intra prediction mode.

[0108] Information indicating whether EMT or AMT is applied (e.g., referred to as an AMT flag) and information indicating the selected transformation type are signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0109] Furthermore, the transform unit 106 may retransform the transform coefficients (transform results). Such retransformation may be referred to as an adaptive secondary transform (AST) or a non-separable secondary transform (NSST). For example, the transform unit 106 performs retransformation for each sub-block (e.g., 4x4 sub-block) included in a block of transform coefficients corresponding to intra-prediction errors. Information indicating whether or not to apply NSST and information regarding the transform matrix used for NSST are signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, picture level, slice level, tile level, or CTU level).

[0110] Here, a separable transformation is a method in which the transformation is performed multiple times by separating the input into directions equal to the number of dimensions, and a non-separable transformation is a method in which, when the input is multidimensional, two or more dimensions are treated as one dimension and the transformation is performed all at once.

[0111] For example, one example of a non-separable transformation is when the input is a 4x4 block, it is treated as a single array with 16 elements, and the transformation process is performed on that array using a 16x16 transformation matrix.

[0112] Similarly, a non-separable transformation is one that treats a 4x4 input block as a single array with 16 elements and then performs multiple Givens rotations on that array (Hypercube Givens Transform).

[0113] [Quantization section] The quantization unit 108 quantizes the transform coefficients output from the transform unit 106. Specifically, the quantization unit 108 scans the transform coefficients of the current block in a predetermined scanning order and quantizes the transform coefficients based on quantization parameters (QP) corresponding to the scanned transform coefficients. The quantization unit 108 then outputs the quantized transform coefficients of the current block (hereinafter referred to as quantized coefficients) to the entropy coding unit 110 and the inverse quantization unit 112.

[0114] The predetermined order is an order for quantizing / dequantizing the transform coefficients. For example, the predetermined scanning order is defined as an ascending order (low frequency to high frequency) or a descending order (high frequency to low frequency).

[0115] The quantization parameter is a parameter that defines the quantization step (quantization width). For example, as the value of the quantization parameter increases, the quantization step also increases. In other words, as the value of the quantization parameter increases, the quantization error also increases.

[0116] [Entropy coding section] The entropy coding unit 110 generates a coded signal (coded bit stream) by variable-length coding the quantized coefficients input from the quantization unit 108. Specifically, the entropy coding unit 110, for example, binarizes the quantized coefficients and arithmetically codes the binary signal.

[0117] [Dequantization section] The inverse quantization unit 112 inverse quantizes the quantized coefficients input from the quantization unit 108. Specifically, the inverse quantization unit 112 inverse quantizes the quantized coefficients of the current block in a predetermined scanning order. The inverse quantization unit 112 then outputs the inverse quantized transform coefficients of the current block to the inverse transform unit 114.

[0118] [Inverse conversion section] The inverse transform unit 114 restores the prediction error by inverse transforming the transform coefficients that are input from the inverse quantization unit 112. Specifically, the inverse transform unit 114 restores the prediction error of the current block by performing an inverse transform on the transform coefficients that corresponds to the transform performed by the transform unit 106. Then, the inverse transform unit 114 outputs the restored prediction error to the adder unit 116.

[0119] Note that the restored prediction error does not match the prediction error calculated by the subtraction unit 104 because information has been lost due to quantization. In other words, the restored prediction error includes a quantization error.

[0120] [Addition section] The adder 116 reconstructs the current block by adding the prediction error input from the inverse transformer 114 and the prediction sample input from the prediction control unit 128. The adder 116 then outputs the reconstructed block to the block memory 118 and the loop filter unit 120. The reconstructed block is sometimes called a local decoded block.

[0121] [Block Memory] The block memory 118 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be coded (hereinafter referred to as a current picture). Specifically, the block memory 118 stores the reconstructed blocks output from the adder 116.

[0122] [Loop filter section] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder 116 and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used in the encoding loop, and includes, for example, a deblocking filter (DF), a sample adaptive offset (SAO), and an adaptive loop filter (ALF).

[0123] ALF applies a least squares error filter to remove coding artifacts, for example, for each 2x2 sub-block in the current block, one filter selected from multiple filters based on local gradient direction and activity.

[0124] Specifically, first, sub-blocks (e.g., 2x2 sub-blocks) are classified into a plurality of classes (e.g., 15 or 25 classes). The sub-blocks are classified based on the gradient direction and activity. For example, a classification value C (e.g., C=5D+A) is calculated using a gradient direction value D (e.g., 0 to 2 or 0 to 4) and a gradient activity value A (e.g., 0 to 4). Then, based on the classification value C, the sub-blocks are classified into a plurality of classes (e.g., 15 or 25 classes).

[0125] The gradient direction value D is derived by, for example, comparing gradients in multiple directions (e.g., horizontal, vertical, and two diagonal directions), and the gradient activity value A is derived by, for example, adding gradients in multiple directions and quantizing the sum.

[0126] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0127] The filter shape used in ALF is, for example, a circularly symmetric shape. FIGS. 4A to 4C are diagrams showing several examples of filter shapes used in ALF. FIG. 4A shows a 5x5 diamond-shaped filter, FIG. 4B shows a 7x7 diamond-shaped filter, and FIG. 4C shows a 9x9 diamond-shaped filter. Information indicating the filter shape is signaled at the picture level. Note that signaling of the information indicating the filter shape does not need to be limited to the picture level, and may be at other levels (e.g., sequence level, slice level, tile level, CTU level, or CU level).

[0128] Whether ALF is turned on or off is determined, for example, at the picture level or the CU level. For example, whether ALF is applied to luminance is determined at the CU level, and whether ALF is applied to chrominance is determined at the picture level. Information indicating whether ALF is turned on or off is signaled at the picture level or the CU level. Note that signaling of information indicating whether ALF is turned on or off does not need to be limited to the picture level or the CU level, and may be at another level (for example, the sequence level, the slice level, the tile level, or the CTU level).

[0129] The coefficient sets of multiple selectable filters (e.g., up to 15 or 25 filters) are signaled at the picture level. Note that the signaling of the coefficient sets does not need to be limited to the picture level, but may also be at other levels (e.g., sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0130] [Frame memory] The frame memory 122 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 122 stores the reconstructed blocks filtered by the loop filter unit 120.

[0131] [Intra prediction section] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also referred to as intra-picture prediction) of the current block with reference to blocks in the current picture stored in the block memory 118. Specifically, the intra prediction unit 124 generates the intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 128.

[0132] For example, the intra prediction unit 124 performs intra prediction using one of a plurality of predefined intra prediction modes. The plurality of intra prediction modes includes one or more non-directional prediction modes and a plurality of directional prediction modes.

[0133] The one or more non-directional prediction modes include, for example, a planar prediction mode and a DC prediction mode defined in the H.265 / High-Efficiency Video Coding (HEVC) standard (Non-Patent Document 1).

[0134] The multiple directional prediction modes include, for example, the 33 prediction modes defined in the H.265 / HEVC standard. Note that the multiple directional prediction modes may also include 32 prediction modes in addition to the 33 directions (65 directional prediction modes in total). Fig. 5A is a diagram showing 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) in intra prediction. Solid arrows represent the 33 directions defined in the H.265 / HEVC standard, and dashed arrows represent the additional 32 directions.

[0135] Note that a luminance block may be referenced in intra prediction of a chrominance block. That is, the chrominance component of the current block may be predicted based on the luminance component of the current block. This type of intra prediction is sometimes called CCLM (cross-component linear model) prediction. An intra prediction mode of a chrominance block that references such a luminance block (e.g., called a CCLM mode) may be added as one of the intra prediction modes for the chrominance block.

[0136] The intra prediction unit 124 may correct pixel values after intra prediction based on gradients of reference pixels in the horizontal / vertical directions. Intra prediction involving such correction is sometimes called PDPC (position dependent intra prediction combination). Information indicating whether PDPC is applied (e.g., called a PDPC flag) is signaled, for example, at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0137] [Inter prediction section] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also referred to as inter prediction) on the current block with reference to a reference picture stored in the frame memory 122 that is different from the current picture. The inter prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) within the current block. For example, the inter prediction unit 126 performs motion estimation on the current block or sub-block within the reference picture. The inter prediction unit 126 then generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., a motion vector) obtained by the motion estimation. The inter prediction unit 126 then outputs the generated inter prediction signal to the prediction control unit 128.

[0138] The motion information used for motion compensation is signaled. For the signaling of the motion vector, a motion vector predictor may be used, i.e., the difference between the motion vector and the motion vector predictor may be signaled.

[0139] Note that an inter-prediction signal may be generated using not only the motion information of the current block obtained by motion estimation, but also the motion information of adjacent blocks. Specifically, an inter-prediction signal may be generated for each sub-block in the current block by weighting and adding a prediction signal based on the motion information obtained by motion estimation and a prediction signal based on the motion information of adjacent blocks. Such inter-prediction (motion compensation) may be called OBMC (overlapped block motion compensation).

[0140] In such an OBMC mode, information indicating the size of a sub-block for OBMC (e.g., called an OBMC block size) is signaled at the sequence level. Also, information indicating whether the OBMC mode is applied (e.g., called an OBMC flag) is signaled at the CU level. Note that the signaling level of this information is not limited to the sequence level and the CU level, and may be other levels (e.g., the picture level, slice level, tile level, CTU level, or sub-block level).

[0141] The OBMC mode will now be described in more detail. Figures 5B and 5C are a flowchart and a conceptual diagram for explaining an outline of the predictive image correction process using the OBMC process.

[0142] First, a predicted image (Pred) is obtained by normal motion compensation using a motion vector (MV) assigned to the block to be coded.

[0143] Next, the motion vector (MV_L) of the coded left adjacent block is applied to the block to be coded to obtain a predicted image (Pred_L), and the predicted image is weighted and superimposed with Pred_L to perform the first correction of the predicted image.

[0144] Similarly, the motion vector (MV_U) of the already coded upper adjacent block is applied to the block to be coded to obtain a predicted image (Pred_U), and the predicted image that has been corrected the first time is weighted and overlaid with Pred_U to perform a second correction of the predicted image, which is then used as the final predicted image.

[0145] Although a two-stage correction method using the left adjacent block and the upper adjacent block has been described here, it is also possible to configure a method in which correction is performed more than two times using the right adjacent block or the lower adjacent block.

[0146] The area to be superimposed does not have to be the pixel area of the entire block, but may be only a part of the area near the block boundary.

[0147] Although the process of correcting a predicted image from one reference picture has been described here, the process is similar when correcting a predicted image from multiple reference pictures. After obtaining corrected predicted images from each reference picture, the obtained predicted images are further superimposed to form the final predicted image.

[0148] The target block to be processed may be a prediction block unit or a sub-block unit obtained by further dividing the prediction block.

[0149] As a method for determining whether to apply OBMC processing, for example, there is a method using obmc_flag, which is a signal indicating whether to apply OBMC processing. As a specific example, an encoding device determines whether a block to be encoded belongs to an area with complex motion, and if it belongs to an area with complex motion, sets the value of obmc_flag to 1 and performs encoding by applying OBMC processing, and if it does not belong to an area with complex motion, sets the value of obmc_flag to 0 and performs encoding without applying OBMC processing. On the other hand, a decoding device decodes obmc_flag described in a stream, and switches whether to apply OBMC processing depending on the value, and performs decoding.

[0150] Alternatively, the motion information may be derived on the decoding device side without being signaled. For example, a merge mode defined in the H.265 / HEVC standard may be used. Alternatively, the motion information may be derived by performing motion estimation on the decoding device side. In this case, the motion estimation is performed without using pixel values of the current block.

[0151] Here, a mode in which motion estimation is performed on the decoding device side will be described. This mode in which motion estimation is performed on the decoding device side is sometimes called a pattern matched motion vector derivation (PMMVD) mode or a frame rate up-conversion (FRUC) mode.

[0152] An example of the FRUC process is shown in Figure 5D. First, a list of multiple candidates (which may be the same as the merge list) each having a predicted motion vector is generated by referring to the motion vectors of coded blocks spatially or temporally adjacent to the current block. Next, a best candidate MV is selected from the multiple candidate MVs registered in the candidate list. For example, an evaluation value of each candidate included in the candidate list is calculated, and one candidate is selected based on the evaluation value.

[0153] Then, a motion vector for the current block is derived based on the motion vector of the selected candidate. Specifically, for example, the motion vector of the selected candidate (best candidate MV) is derived as the motion vector for the current block as is. Also, for example, the motion vector for the current block may be derived by performing pattern matching in a peripheral area of a position in a reference picture corresponding to the motion vector of the selected candidate. That is, a search is performed in a similar manner in a peripheral area of the best candidate MV, and if an MV with a better evaluation value is found, the best candidate MV may be updated to the MV and used as the final MV for the current block. Note that a configuration may be adopted in which this process is not performed.

[0154] The same processing may be performed when processing is performed in sub-block units.

[0155] The evaluation value is calculated by finding the difference between the reconstructed image and a predetermined area by pattern matching between the area in the reference picture corresponding to the motion vector. The evaluation value may be calculated using other information in addition to the difference.

[0156] As the pattern matching, first pattern matching or second pattern matching is used. The first pattern matching and second pattern matching are sometimes called bilateral matching and template matching, respectively.

[0157] In the first pattern matching, pattern matching is performed between two blocks in two different reference pictures that are along the motion trajectory of the current block. Therefore, in the first pattern matching, an area in another reference picture that is along the motion trajectory of the current block is used as a predetermined area for calculating the evaluation value of the candidate.

[0158] FIG. 6 is a diagram illustrating an example of pattern matching (bilateral matching) between two blocks along a motion trajectory. As shown in FIG. 6, in the first pattern matching, two motion vectors (MV0, MV1) are derived by searching for the most closely matched pair of two blocks along the motion trajectory of a current block (Cur block) in two different reference pictures (Ref0, Ref1). Specifically, for the current block, a difference is derived between a reconstructed image at a specified position in a first coded reference picture (Ref0) specified by a candidate MV and a reconstructed image at a specified position in a second coded reference picture (Ref1) specified by a symmetric MV obtained by scaling the candidate MV by the display time interval, and an evaluation value is calculated using the obtained difference value. The candidate MV with the best evaluation value among multiple candidate MVs may be selected as the final MV.

[0159] Under the assumption of continuous motion trajectories, motion vectors (MV0, MV1) pointing to two reference blocks are proportional to the temporal distances (TD0, TD1) between a current picture (CurPic) and two reference pictures (Ref0, Ref1). For example, if the current picture is located between two reference pictures temporally and the temporal distances from the current picture to the two reference pictures are equal, the first pattern matching derives bidirectional motion vectors that are mirror-symmetric.

[0160] In the second pattern matching, pattern matching is performed between a template in the current picture (a block adjacent to the current block in the current picture (e.g., an upper and / or left adjacent block)) and a block in the reference picture. Therefore, in the second pattern matching, the block adjacent to the current block in the current picture is used as a predetermined area for calculating the evaluation value of the candidate.

[0161] 7 is a diagram illustrating an example of pattern matching (template matching) between a template in a current picture and a block in a reference picture. As shown in FIG. 7, in the second pattern matching, a motion vector of a current block is derived by searching a reference picture (Ref0) for a block that best matches a block adjacent to a current block (Cur block) in the current picture (Cur Pic). Specifically, a difference is derived between a reconstructed image of both or either of the coded areas adjacent to the left and / or above the current block and a reconstructed image at the same position in the coded reference picture (Ref0) specified by a candidate MV, an evaluation value is calculated using the obtained difference value, and the candidate MV with the best evaluation value among the multiple candidate MVs is selected as the best candidate MV.

[0162] Information indicating whether such a FRUC mode is applied (e.g., called an FRUC flag) is signaled at the CU level. Furthermore, when the FRUC mode is applied (e.g., when the FRUC flag is true), information indicating a pattern matching method (first pattern matching or second pattern matching) (e.g., called an FRUC mode flag) is signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, the picture level, the slice level, the tile level, the CTU level, or the sub-block level).

[0163] Here, we will explain a mode in which motion vectors are derived based on a model that assumes uniform linear motion. This mode is sometimes called BIO (bi-directional optical flow) mode.

[0164] Fig. 8 is a diagram illustrating a model assuming uniform linear motion. In Fig. 8, (vx, vy) indicate a velocity vector, and τ0 and τ1 indicate the temporal distances between the current picture (Cur Pic) and two reference pictures (Ref0, Ref1), respectively. (MVx0, MVy0) indicate the motion vector corresponding to reference picture Ref0, and (MVx1, MVy1) indicate the motion vector corresponding to reference picture Ref1.

[0165] In this case, under the assumption of uniform linear motion of the velocity vector (vx, vy), (MVx0, MVy0) and (MVx1, MVy1) are expressed as (vxτ0, vyτ0) and (-vxτ1, -vyτ1), respectively, and the following optical flow equation (1) holds.

[0166]

number

[0167] Here, I(k) denotes the luminance value of reference image k (k=0,1) after motion compensation. This optical flow equation indicates that the sum of (i) the time derivative of the luminance value, (ii) the product of the horizontal velocity and the horizontal component of the spatial gradient of the reference image, and (iii) the product of the vertical velocity and the vertical component of the spatial gradient of the reference image is equal to zero. Based on a combination of this optical flow equation and Hermite interpolation, block-wise motion vectors obtained from a merge list or the like are corrected pixel by pixel.

[0168] Note that the decoding device may derive motion vectors using a method other than that based on a model assuming constant-velocity linear motion. For example, a motion vector may be derived for each sub-block based on the motion vectors of multiple adjacent blocks.

[0169] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of multiple neighboring blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0170] 9A is a diagram illustrating the derivation of motion vectors for each sub-block based on the motion vectors of multiple adjacent blocks. In FIG. 9A, the current block includes 16 4x4 sub-blocks. Here, a motion vector v0 for the upper left corner control point of the current block is derived based on the motion vectors of the adjacent blocks, and a motion vector v1 for the upper right corner control point of the current block is derived based on the motion vectors of the adjacent sub-blocks. Then, using the two motion vectors v0 and v1, the motion vectors (vx, vy) of each sub-block within the current block are derived according to the following equation (2):

[0171]

number

[0172] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting coefficient.

[0173] Such an affine motion compensation prediction mode may include several modes in which the methods of deriving the motion vectors of the upper-left and upper-right corner control points are different. Information indicating such an affine motion compensation prediction mode (e.g., called an affine flag) is signaled at the CU level. Note that the signaling of the information indicating this affine motion compensation prediction mode does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, the picture level, the slice level, the tile level, the CTU level, or the sub-block level).

[0174] [Predictive control unit] The prediction control unit 128 selects either the intra-prediction signal or the inter-prediction signal, and outputs the selected signal to the subtraction unit 104 and the addition unit 116 as a prediction signal.

[0175] Here, an example of deriving a motion vector for a picture to be coded in merge mode will be described. Fig. 9B is a diagram for explaining an overview of the motion vector derivation process in merge mode.

[0176] First, a prediction MV list is generated in which prediction MV candidates are registered. The prediction MV candidates include spatially adjacent prediction MVs, which are MVs held by multiple coded blocks spatially located around the block to be coded, temporally adjacent prediction MVs, which are MVs held by blocks in the vicinity of the block to be coded projected onto the coded reference picture, joint prediction MVs, which are MVs generated by combining the MV values of the spatially adjacent prediction MVs and the temporally adjacent prediction MVs, and zero prediction MVs, which are MVs with a value of zero.

[0177] Next, one prediction MV is selected from the plurality of prediction MVs registered in the prediction MV list, and is determined as the MV for the block to be coded.

[0178] Furthermore, the variable length coding unit encodes the stream by describing merge_idx, which is a signal indicating which predicted MV has been selected.

[0179] Note that the predicted MVs registered in the predicted MV list described in Figure 9B are just an example, and the number may be different from the number shown in the figure, the configuration may not include some of the types of predicted MVs shown in the figure, or the configuration may include predicted MVs other than the types of predicted MVs shown in the figure.

[0180] The final MV may be determined by performing the DMVR process, which will be described later, using the MV of the block to be coded derived in the merge mode.

[0181] Here, an example of determining the MV using the DMVR process will be described.

[0182] FIG. 9C is a conceptual diagram for explaining an outline of the DMVR process.

[0183] First, the optimal MVP set for the block to be processed is set as a candidate MV, and reference pixels are obtained from the first reference picture, which is a processed picture in the L0 direction, and the second reference picture, which is a processed picture in the L1 direction, according to the candidate MV, and a template is generated by averaging each reference pixel.

[0184] Next, the template is used to search the surrounding areas of the candidate MVs in the first and second reference pictures, and the MV with the smallest cost is determined as the final MV. The cost value is calculated using the difference between each pixel value of the template and each pixel value of the search area, the MV value, etc.

[0185] The outline of the processing described here is basically the same for the encoding device and the decoding device.

[0186] Note that other processing may be used instead of the processing described here, as long as it is processing that can search the vicinity of the candidate MV and derive the final MV.

[0187] Here, a mode for generating a predicted image using LIC processing will be described.

[0188] FIG. 9D is a diagram for explaining an outline of a predicted image generation method using luminance correction processing by LIC processing.

[0189] First, an MV for obtaining a reference image corresponding to a block to be coded is derived from a reference picture that is a coded picture.

[0190] Next, for the block to be coded, the luminance pixel values of the coded surrounding reference areas adjacent to the left and above and the luminance pixel values at the equivalent positions in the reference picture specified by the MV are used to extract information indicating how the luminance values have changed between the reference picture and the picture to be coded, and a luminance correction parameter is calculated.

[0191] A predicted image for the block to be coded is generated by performing luminance correction processing on a reference image in a reference picture specified by the MV using the luminance correction parameters.

[0192] The shape of the peripheral reference region in FIG. 9D is an example, and other shapes may be used.

[0193] Although the process of generating a predicted image from one reference picture has been described here, the process is similar when generating a predicted image from multiple reference pictures, and a luminance correction process is performed in a similar manner on the reference images obtained from each reference picture before generating a predicted image.

[0194] As a method for determining whether to apply LIC processing, for example, there is a method using lic_flag, which is a signal indicating whether to apply LIC processing. As a specific example, an encoding device determines whether the encoding target block belongs to an area where a luminance change occurs, and if it belongs to an area where a luminance change occurs, sets the value of lic_flag to 1 and performs encoding by applying LIC processing, and if it does not belong to an area where a luminance change occurs, sets the value of lic_flag to 0 and performs encoding without applying LIC processing. On the other hand, a decoding device decodes lic_flag described in the stream, and switches whether to apply LIC processing depending on the value, and performs decoding.

[0195] As another method for determining whether to apply LIC processing, for example, there is also a method for determining whether LIC processing has been applied to surrounding blocks.As a specific example, when the block to be coded is in merge mode, it is determined whether the surrounding coded blocks selected when deriving MV in merge mode processing have been coded using LIC processing, and depending on the result, whether to apply LIC processing is switched and coded.In addition, in this example, the process in decoding is exactly the same.

[0196] [Overview of the decoding device] Next, an overview will be given of a decoding device capable of decoding the coded signal (coded bitstream) output from the above coding device 100. Fig. 10 is a block diagram showing the functional configuration of a decoding device 200 according to Embodiment 1. The decoding device 200 is a video / image decoding device that decodes video / images on a block-by-block basis.

[0197] As shown in FIG. 10, the decoding device 200 includes an entropy decoding unit 202, an inverse quantization unit 204, an inverse transform unit 206, an addition unit 208, a block memory 210, a loop filter unit 212, a frame memory 214, an intra prediction unit 216, an inter prediction unit 218, and a prediction control unit 220.

[0198] The decoding device 200 is realized by, for example, a general-purpose processor and memory. In this case, when a software program stored in the memory is executed by the processor, the processor functions as the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220. Alternatively, the decoding device 200 may be realized as one or more dedicated electronic circuits corresponding to the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220.

[0199] Each component included in the decoding device 200 will be described below.

[0200] [Entropy Decoding] The entropy decoding unit 202 entropy-decodes the coded bitstream. Specifically, the entropy decoding unit 202 arithmetically decodes the coded bitstream into a binary signal. The entropy decoding unit 202 then debinarizes the binary signal. As a result, the entropy decoding unit 202 outputs quantized coefficients to the inverse quantization unit 204 on a block-by-block basis.

[0201] [Dequantization section] The inverse quantization unit 204 inverse quantizes the quantized coefficients of a block to be decoded (hereinafter referred to as a current block) that is input from the entropy decoding unit 202. Specifically, the inverse quantization unit 204 inverse quantizes each quantized coefficient of the current block based on a quantization parameter corresponding to the quantized coefficient. The inverse quantization unit 204 then outputs the inverse quantized coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0202] [Inverse conversion section] The inverse transform unit 206 restores the prediction error by inverse transforming the transform coefficients input from the inverse quantization unit 204 .

[0203] For example, if the information interpreted from the encoded bitstream indicates that EMT or AMT is to be applied (e.g., the AMT flag is true), the inverse transform unit 206 inverse transforms the transform coefficients of the current block based on the interpreted information indicating the transform type.

[0204] Also, for example, if the information decoded from the coded bitstream indicates that NSST is to be applied, then inverse transform unit 206 applies an inverse re-transform to the transform coefficients.

[0205] [Adder] The adder 208 reconstructs the current block by adding the prediction error input from the inverse transformer 206 and the prediction sample input from the prediction control unit 220. The adder 208 then outputs the reconstructed block to the block memory 210 and the loop filter unit 212.

[0206] [Block Memory] The block memory 210 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be decoded (hereinafter referred to as a current picture). Specifically, the block memory 210 stores the reconstructed blocks output from the adder 208.

[0207] [Loop filter section] The loop filter unit 212 applies a loop filter to the block reconstructed by the adder unit 208, and outputs the filtered reconstructed block to a frame memory 214, a display device, or the like.

[0208] If the information indicating ALF on / off read from the encoded bitstream indicates that ALF is on, one filter is selected from multiple filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0209] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 214 stores the reconstructed blocks filtered by the loop filter unit 212.

[0210] [Intra prediction section] The intra prediction unit 216 generates a prediction signal (intra prediction signal) by performing intra prediction based on the intra prediction mode interpreted from the encoded bitstream, by referring to blocks in the current picture stored in the block memory 210. Specifically, the intra prediction unit 216 generates the intra prediction signal by performing intra prediction by referring to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0211] Note that when an intra prediction mode that references a luminance block in intra prediction of a chrominance block is selected, the intra prediction unit 216 may predict the chrominance component of the current block based on the luminance component of the current block.

[0212] Furthermore, when information interpreted from the coded bitstream indicates the application of PDPC, the intra prediction unit 216 corrects pixel values after intra prediction based on the gradients of reference pixels in the horizontal and vertical directions.

[0213] [Inter prediction section] The inter prediction unit 218 predicts the current block by referring to a reference picture stored in the frame memory 214. The prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) within the current block. For example, the inter prediction unit 218 generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) interpreted from the coded bitstream, and outputs the inter prediction signal to the prediction control unit 220.

[0214] In addition, if the information interpreted from the encoded bitstream indicates that the OBMC mode is to be applied, the inter prediction unit 218 generates an inter prediction signal using not only the motion information of the current block obtained by motion search, but also the motion information of adjacent blocks.

[0215] Furthermore, if the information interpreted from the coded bitstream indicates that the FRUC mode is to be applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) interpreted from the coded bitstream. Then, the inter prediction unit 218 performs motion compensation using the derived motion information.

[0216] Furthermore, when the BIO mode is applied, the inter prediction unit 218 derives a motion vector based on a model assuming constant-velocity linear motion. Furthermore, when information interpreted from the coded bitstream indicates that the affine motion compensation prediction mode is to be applied, the inter prediction unit 218 derives a motion vector for each sub-block based on the motion vectors of multiple adjacent blocks.

[0217] [Predictive control unit] The prediction control unit 220 selects either the intra-prediction signal or the inter-prediction signal, and outputs the selected signal to the addition unit 208 as a prediction signal.

[0218] [Transformation, quantization, and encoding processes in the encoding device] Next, the transform processing, quantization processing, and encoding processing performed by the transform unit 106, quantization unit 108, and entropy encoding unit 110 of the encoding device 100 configured as above will be described in detail with reference to the drawings.

[0219] Fig. 11 is a flowchart showing an example of a transform process, a quantization process, and a coding process according to Embodiment 1. The steps shown in Fig. 11 are performed by the transform unit 106, the quantization unit 108, or the entropy coding unit 110 of the coding device 100 according to Embodiment 1.

[0220] First, the transform unit 106 performs a linear transform from the residual of the block to be coded to linear coefficients (S101). The linear transform is, for example, a separable transform. Specifically, the linear transform is, for example, a DCT or a DST.

[0221] Next, the transform unit 106 determines whether to perform a secondary transform on the primary coefficients (S102). That is, the transform unit 106 determines whether to apply a secondary transform to the encoding target block. For example, the transform unit 106 determines whether to perform a secondary transform based on a cost based on the difference between the original image and the reconstructed image and / or the code amount. Note that the determination of whether to perform a secondary transform is not limited to such a determination based on the cost. For example, the determination of whether to perform a secondary transform may be based on a prediction mode, a block size, a picture type, or any combination thereof.

[0222] Here, if it is determined that secondary transformation is not to be performed (No in S102), the quantization unit 108 calculates quantized primary coefficients by performing first quantization on the primary coefficients (S103). The first quantization is weighted quantization using a first quantization matrix. In the first quantization, a quantization step weighted for each coefficient by the first quantization matrix is used. The first quantization matrix is a weighting matrix for adjusting the magnitude of the quantization step for each coefficient. The size of the first quantization matrix matches the size of the block to be coded. In other words, the number of components of the first quantization matrix matches the number of coefficients in the block to be coded.

[0223] On the other hand, if it is determined that a secondary transformation is to be performed (Yes in S102), the transformation unit 106 performs a secondary transformation from the linear coefficients to the secondary coefficients (S104). The secondary transformation uses a basis different from the basis of the linear transformation. For example, the secondary transformation is a non-separable transformation. The basis used in the secondary transformation is, for example, predefined by a standard.

[0224] Thereafter, the quantization unit 108 calculates quantized secondary coefficients by performing second quantization different from the first quantization on the secondary coefficients (S105). The second quantization different from the first quantization means that the parameters or quantization methods used for the first quantization and the second quantization are different. The parameters used for the quantization are, for example, a quantization matrix or a quantization parameter.

[0225] In this embodiment, the second quantization uses a quantization parameter different from that used in the first quantization. Specifically, the second quantization is weighted quantization using a second quantization matrix different from the first quantization matrix. The second quantization uses a quantization step weighted for each coefficient by the second quantization matrix.

[0226] The second quantization matrix is a weighting matrix for adjusting the size of the quantization step for each coefficient. The second quantization matrix has component values different from those of the first quantization matrix. The size of the second quantization matrix matches the size of the block to be coded. In other words, the number of components of the second quantization matrix matches the number of coefficients of the block to be coded.

[0227] The entropy coding unit 110 generates a coded bitstream by entropy coding the quantized primary coefficients or the quantized secondary coefficients (S106). At this time, the entropy coding unit 110 writes the first quantization matrix and the second quantization matrix into the coded bitstream.

[0228] In addition, when secondary transformation is performed only on one or more first primary coefficients included in the primary coefficients in the block to be coded, only one or more first component values of the second quantization matrix corresponding to the one or more first primary coefficients to which secondary transformation is performed are written into the coded bitstream, and one or more second component values of the second quantization matrix corresponding to the one or more second primary coefficients to which secondary transformation is not performed are not written into the coded bitstream, but may be common to the corresponding component values of the first quantization matrix. In other words, each of the one or more second component values of the second quantization matrix may be the same as the corresponding component value of the first quantization matrix. In addition, the one or more first primary coefficients may be, for example, coefficients in the low-frequency region, and the one or more second primary coefficients may be, for example, coefficients in the high-frequency region.

[0229] The entropy coding unit 110 may also write information indicating whether or not to apply secondary transformation to the current block to be coded into the coded bitstream.

[0230] Note that the positions of the first quantization matrix and the second quantization matrix in the coded bitstream are not particularly limited. For example, the first quantization matrix and the second quantization matrix may be written in (i) a video parameter set (VPS), (ii) a sequence parameter set (SPS), (iii) a picture parameter set (PPS), (iv) a slice header, or (v) a video system setting parameter, as shown in Fig. 12 .

[0231] As described above, in this embodiment, different quantization is performed depending on whether or not secondary transformation is performed. That is, the quantization unit 108 switches between first quantization and second quantization based on whether or not secondary transformation is applied to the block to be coded. In particular, in this embodiment, different quantization matrices are used depending on whether or not secondary transformation is performed. That is, in this embodiment, the quantization unit 108 performs quantization by switching between the first quantization matrix and the second quantization matrix based on whether or not secondary transformation is applied to the block to be coded.

[0232] [Decoding process, inverse quantization process, and inverse transform process in the decoding device] Next, the decoding process, inverse quantization process, and inverse transform process performed by the entropy decoding unit 202, inverse quantization unit 204, and inverse transform unit 206 of the decoding device 200 according to this embodiment will be specifically described with reference to the drawings.

[0233] 13 is a flowchart showing an example of the decoding process, the inverse quantization process, and the inverse transform process according to Embodiment 1. Each step shown in FIG.

[0234] First, the entropy decoding unit 202 entropy-decodes the coded quantized coefficients of the block to be decoded from the coded bitstream (S201). The decoded quantized coefficients are primary quantized coefficients or secondary quantized coefficients. The entropy decoding unit 202 further decodes a first quantization matrix and a second quantization matrix from the coded bitstream. Note that if an inverse secondary transform is performed only on one or more first secondary coefficients included in the secondary coefficients of the block to be decoded, only one or more first component values of the second quantization matrix corresponding to the one or more first secondary coefficients to be subjected to the inverse secondary transform may be decoded from the coded bitstream. For one or more second component values of the second quantization matrix corresponding to the one or more second secondary coefficients not to be subjected to the inverse secondary transform, each of the second component values may be the same as the corresponding component value of the first quantization matrix. In other words, each of the one or more second component values of the second quantization matrix may be identical to the corresponding component value of the first quantization matrix. Furthermore, the entropy decoding unit 202 may decode information indicating whether or not to apply an inverse secondary transform to the block to be decoded from the coded bitstream.

[0235] The inverse transform unit 206 determines whether to perform an inverse secondary transform based on the coded bitstream (S202). That is, the inverse transform unit 206 determines whether to apply an inverse secondary transform to the block to be decoded. For example, the inverse transform unit 206 determines whether to perform an inverse secondary transform based on information interpreted from the coded bitstream that indicates whether to apply an inverse secondary transform.

[0236] Here, if it is determined that the inverse secondary transform is not to be performed (No in S202), the inverse quantization unit 204 calculates primary coefficients by performing first inverse quantization on the decoded quantized coefficients (S203). The first inverse quantization is inverse quantization of the first quantization performed by the encoding device 100. In this embodiment, the first inverse quantization is weighted inverse quantization using a first quantization matrix.

[0237] On the other hand, if it is determined that an inverse secondary transform is to be performed (Yes in S202), the inverse quantization unit 204 calculates secondary coefficients by performing second inverse quantization, which is different from the first inverse quantization, on the decoded quantized coefficients (S204). The second inverse quantization is the inverse quantization of the second quantization performed in the encoding device 100. In this embodiment, the second inverse quantization is weighted inverse quantization using a second quantization matrix. Thereafter, the inverse transform unit 206 performs an inverse secondary transform from the secondary coefficients calculated by the second inverse quantization to primary coefficients (S205). The inverse secondary transform is the inverse transform of the secondary transform performed in the encoding device 100.

[0238] The inverse transform unit 206 performs an inverse primary transform from the primary coefficients obtained by the inverse secondary transform or the first inverse quantization to the residual of the block to be decoded (S206). The inverse primary transform is the inverse transform of the primary transform performed in the encoding device 100.

[0239] As described above, in this embodiment, different inverse quantization is performed depending on whether or not an inverse secondary transform is performed. That is, the inverse quantization unit 204 switches between the first inverse quantization and the second inverse quantization based on whether or not an inverse secondary transform is applied to the block to be decoded. In particular, in this embodiment, different quantization matrices are used depending on whether or not an inverse secondary transform is performed. That is, in this embodiment, the inverse quantization unit 204 performs inverse quantization by switching between the first quantization matrix and the second quantization matrix based on whether or not an inverse secondary transform is applied.

[0240] [Effects, etc.] As described above, the encoding device 100 and decoding device 200 according to this embodiment can perform different quantization / inverse quantization depending on whether a secondary transform / inverse secondary transform is applied to the current block. Secondary coefficients obtained by secondary transforming primary coefficients expressed in a first space are expressed in a secondary space, not a primary space. Therefore, even if the quantization / inverse quantization for the primary coefficients is applied to the secondary coefficients, it is difficult to improve coding efficiency while suppressing degradation of subjective image quality. For example, quantization for minimizing loss of low-frequency components to suppress degradation of subjective image quality and increasing loss of high-frequency components to improve coding efficiency differs between the primary space and the secondary space. Therefore, by performing different quantization / inverse quantization depending on whether a secondary transform / inverse secondary transform is applied to the current block, it is possible to improve coding efficiency while suppressing degradation of subjective image quality, compared to when a common quantization / inverse quantization is performed.

[0241] Furthermore, according to the encoding device 100 and the decoding device 200 of this embodiment, weighted quantization / inverse quantization using a first quantization matrix can be performed as the first quantization / first inverse quantization. Furthermore, weighted quantization / inverse quantization using a second quantization matrix different from the first quantization matrix can be performed as the second quantization / second inverse quantization. Therefore, a first quantization matrix corresponding to a primary space can be used for quantization / inverse quantization of primary coefficients, and a second quantization matrix corresponding to a secondary space can be used for quantization / inverse quantization of secondary coefficients. Therefore, it is possible to improve encoding efficiency while suppressing degradation of subjective image quality, whether or not a secondary transform / inverse secondary transform is applied.

[0242] Furthermore, according to the encoding device 100 and decoding device 200 of this embodiment, the first quantization matrix and the second quantization matrix can be included in the encoded bitstream. Therefore, the first quantization matrix and the second quantization matrix can be adaptively determined depending on the original image, and it is possible to improve the encoding efficiency while suppressing the deterioration of subjective image quality.

[0243] In this embodiment, the first quantization matrix and the second quantization matrix are included in the coded bitstream, but this is not limiting. For example, the first quantization matrix and the second quantization matrix may be transmitted from the coding device to the decoding device separately from the coded bitstream. Furthermore, for example, the first quantization matrix and the second quantization matrix may be defined in advance in a standard specification. In this case, the first quantization matrix and the second quantization matrix may also be referred to as default matrices. Furthermore, for example, the first quantization matrix and the second quantization matrix may be selected from a plurality of default matrices based on a given profile, level, or the like.

[0244] This eliminates the need to include the first quantization matrix and the second quantization matrix in the coded bitstream, making it possible to reduce the amount of code required for the first quantization matrix and the second quantization matrix.

[0245] In this embodiment, a case has been described in which one base is fixedly used in the secondary transform / inverse secondary transform, but the present invention is not limited to this. For example, a plurality of predetermined bases may be selectively used in the secondary transform / inverse secondary transform. In this case, for example, the coded bitstream may include a plurality of second quantization matrices corresponding to the plurality of bases. Then, in the second quantization / second inverse quantization, a second quantization matrix corresponding to the base used in the secondary transform / inverse secondary transform may be selected from the plurality of second quantization matrices.

[0246] This allows second quantization / second inverse quantization to be performed using a second quantization matrix corresponding to the basis used in the secondary transform / inverse secondary transform. The characteristics of the secondary space expressing the secondary coefficients differ depending on the basis used in the secondary transform / inverse secondary transform. Therefore, by performing second quantization / second inverse quantization using a second quantization matrix corresponding to the basis used in the secondary transform / inverse secondary transform, second quantization / second inverse quantization can be performed using a quantization matrix that better corresponds to the secondary space, and coding efficiency can be improved while suppressing degradation of subjective image quality.

[0247] (Embodiment 2) Next, a description will be given of embodiment 2. This embodiment differs from embodiment 1 above in that the second quantization matrix used in second quantization is derived from the first quantization matrix used in first quantization. Hereinafter, this embodiment will be specifically described with reference to the drawings, focusing on the differences from embodiment 1 above.

[0248] [Transformation, quantization, and encoding processes in the encoding device] The transform processing, quantization processing, and encoding processing performed by the transform unit 106, the quantization unit 108, and the entropy encoding unit 110 of the encoding device 100 according to the second embodiment will be specifically described with reference to the drawings.

[0249] Fig. 14 is a flowchart showing an example of a transform process, a quantization process, and a coding process according to Embodiment 2. In Fig. 14, the processes that are substantially the same as those in Fig. 11 are given the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0250] In this embodiment, after the secondary transformation is performed (S104), the quantization unit 108 derives a second quantization matrix from the first quantization matrix (S111). For example, the quantization unit 108 derives the second quantization matrix by applying the secondary transformation to the first quantization matrix. In other words, the quantization unit 108 transforms the first quantization matrix using the basis used in the secondary transformation of the current block to be coded.

[0251] In addition, when secondary transformation is performed only on one or more first primary coefficients included in the primary coefficients in the block to be coded, one or more first component values of the second quantization matrix corresponding to the one or more first primary coefficients on which secondary transformation is performed may be derived from the first quantization matrix, and one or more second component values of the second quantization matrix corresponding to the one or more second primary coefficients on which secondary transformation is not performed may each be common to the corresponding component value of the first quantization matrix. In other words, one or more second component values of the second quantization matrix may each be the same as the corresponding component value of the first quantization matrix.

[0252] The quantization unit 108 calculates quantized secondary coefficients by performing second quantization on the secondary coefficients (S105). In this second quantization, the second quantization matrix derived in step S111 is used.

[0253] The entropy coding unit 110 generates a coded bitstream by entropy coding the quantized primary coefficients or the quantized secondary coefficients (S112). Furthermore, in this embodiment, the entropy coding unit 110 writes the first quantization matrix into the coded bitstream. Conversely, the entropy coding unit 110 does not write the second quantization matrix into the coded bitstream.

[0254] In this way, the quantization unit 108 performs quantization by switching between the first quantization matrix and the second quantization matrix based on whether or not secondary transformation is applied to the current block to be coded. At this time, the quantization unit 108 derives the second quantization matrix from the first quantization matrix.

[0255] [Decoding process, inverse quantization process, and inverse transform process in the decoding device] Next, the decoding process, inverse quantization process, and inverse transform process performed by the entropy decoding unit 202, inverse quantization unit 204, and inverse transform unit 206 of the decoding device 200 according to this embodiment will be specifically described with reference to the drawings.

[0256] Fig. 15 is a flowchart showing an example of a decoding process, an inverse quantization process, and an inverse transform process according to Embodiment 2. In Fig. 15, the same processes as those in Fig. 13 are denoted by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0257] First, the entropy decoding unit 202 decodes the coded quantization coefficients included in the coded bitstream (S211). At this time, the entropy decoding unit 202 reads the first quantization matrix from the coded bitstream.

[0258] The inverse transform unit 206 determines whether or not to perform inverse secondary transform based on the coded bitstream (S202), as in the first embodiment. If it is determined that inverse secondary transform is not to be performed (No in S202), the inverse quantization unit 204 performs first inverse quantization on the decoded quantized coefficients (S203), as in the first embodiment.

[0259] On the other hand, if it is determined that an inverse secondary transform is to be performed (Yes in S202), the inverse quantization unit 204 derives a second quantization matrix from the first quantization matrix (S212). Specifically, the inverse quantization unit 204 derives the second quantization matrix using the same method as the encoding device 100. For example, the inverse quantization unit 204 derives the second quantization matrix by applying a secondary transform to the first quantization matrix. That is, the inverse quantization unit 204 transforms the first quantization matrix using the basis used for the secondary transform of the block to be decoded. Note that, if the inverse secondary transform is to be performed only on one or more first secondary coefficients included in the secondary coefficients in the block to be decoded, one or more first component values of the second quantization matrix corresponding to the one or more first secondary coefficients to which the inverse secondary transform is to be performed may be derived from the first quantization matrix, and one or more second component values of the second quantization matrix corresponding to the one or more second secondary coefficients to which the inverse secondary transform is not to be performed may each be the same as the corresponding component value of the first quantization matrix. That is, each of the one or more second component values of the second quantization matrix may match a corresponding component value of the first quantization matrix.

[0260] Then, the processes from step S204 onwards are carried out.

[0261] In this way, the inverse quantization unit 204 performs inverse quantization by switching between the first quantization matrix and the second quantization matrix based on whether or not the inverse secondary transform is applied to the block to be decoded. At this time, the inverse quantization unit 204 derives the second quantization matrix from the first quantization matrix. Therefore, even if the second quantization matrix is not included in the coded bitstream, the decoding device 200 can perform second inverse quantization.

[0262] [Effects, etc.] As described above, according to encoding device 100 and decoding device 200 of this embodiment, the second quantization matrix can be derived from the first quantization matrix. This eliminates the need to transmit the second quantization matrix to the decoding device, thereby improving encoding efficiency.

[0263] Furthermore, according to encoding device 100 and decoding device 200 of this embodiment, it is possible to derive a second quantization matrix by applying a secondary transformation to a first quantization matrix. Therefore, it is possible to transform a first quantization matrix corresponding to a primary space into a second quantization matrix corresponding to a secondary space, thereby improving encoding efficiency while suppressing degradation of subjective image quality.

[0264] (Modification of the second embodiment) In the present embodiment, an example of applying a secondary transformation directly to a first quantization matrix has been described as a method of deriving a second quantization matrix, but the present invention is not limited to this. Another example of a method of deriving a second quantization matrix will be described below with reference to FIG. 16 .

[0265] 16 is a flowchart showing an example of a process for deriving a second quantization matrix in a modification of Embodiment 2. This flowchart shows an example of the process in step S111 in FIG. 14 and step S212 in FIG.

[0266] In FIG. 16 , the quantization unit 108 or the inverse quantization unit 204 derives a third quantization matrix from a first quantization matrix (S301). At this time, the smaller the corresponding component value of the first quantization matrix, the larger the component value of the third quantization matrix. In other words, as the component value of the first quantization matrix increases, the corresponding component value of the third quantization matrix decreases. In other words, the component values of the first quantization matrix and the third quantization matrix have a monotonically decreasing relationship. For example, the component value of the third quantization matrix is the reciprocal of the corresponding component value of the first quantization matrix.

[0267] Next, the quantization unit 108 or the inverse quantization unit 204 derives a fourth quantization matrix by applying a secondary transformation to the third quantization matrix (S302). That is, the quantization unit 108 or the inverse quantization unit 204 transforms the third quantization matrix using the basis used in the secondary transformation of the current block.

[0268] Finally, the quantization unit 108 or the inverse quantization unit 204 derives a fifth quantization matrix from the fourth quantization matrix as the second quantization matrix (S303). At this time, the smaller the corresponding component value of the fourth quantization matrix, the larger the component value of the fifth quantization matrix. In other words, as the component value of the fourth quantization matrix increases, the corresponding component value of the fifth quantization matrix decreases. In other words, the component values of the fourth quantization matrix and the fifth quantization matrix have a monotonically decreasing relationship. For example, the component value of the fifth quantization matrix is the reciprocal of the corresponding component value of the fourth quantization matrix.

[0269] By deriving the second quantization matrix as described above, it is possible to reduce the influence of rounding errors during secondary transformation on components having relatively small values included in the first quantization matrix. In other words, it is possible to reduce the influence of rounding errors on the values of components applied to coefficients for which loss is desired to be reduced in order to suppress degradation of subjective image quality. Therefore, it is possible to further suppress degradation of subjective image quality.

[0270] Furthermore, the reciprocal of the corresponding component value of the first quantization matrix / fourth quantization matrix can be used as each component value of the third quantization matrix / fifth quantization matrix. Therefore, the component value can be derived with simple calculations, and the processing load or processing time for deriving the second quantization matrix can be reduced.

[0271] (Embodiment 3) Next, a third embodiment will be described. This embodiment differs from the first embodiment in that, when a secondary transformation is performed, secondary coefficients are quantized without using a quantization matrix. Hereinafter, this embodiment will be specifically described with reference to the drawings, focusing on the differences from the first embodiment.

[0272] [Transformation, quantization, and encoding processes in the encoding device] The transform processing, quantization processing, and encoding processing performed by the transform unit 106, quantization unit 108, and entropy encoding unit 110 of the encoding device 100 according to the third embodiment will be specifically described with reference to the drawings.

[0273] Fig. 17 is a flowchart showing an example of a transform process, a quantization process, and a coding process according to Embodiment 3. In Fig. 17, the processes that are substantially the same as those in Fig. 11 are given the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0274] After the secondary transformation from the primary coefficients to the secondary coefficients (S104), the quantization unit 108 calculates quantized secondary coefficients by performing second quantization on the secondary coefficients, which is different from the first quantization (S121). In this embodiment, the second quantization is unweighted quantization that does not use a quantization matrix. That is, the second quantization divides each secondary coefficient by a quantization step that is common to the secondary coefficients of the block to be coded. The common quantization step is derived from a quantization parameter for the block to be coded. Specifically, the common quantization step is a constant that is fixed for all secondary coefficients of the block to be coded. That is, the common quantization step is a constant that does not depend on the position or order of the secondary coefficients.

[0275] As described above, in this embodiment, the quantization unit 108 switches between weighted quantization and non-weighted quantization based on whether or not secondary transformation is applied to the current block to be coded.

[0276] [Decoding process, inverse quantization process, and inverse transform process in the decoding device] Next, the decoding process, the inverse quantization process, and the inverse transform process performed by the entropy decoding unit 202, the inverse quantization unit 204, and the inverse transform unit 206 of the decoding device 200 according to the third embodiment will be specifically described with reference to the drawings.

[0277] Fig. 18 is a flowchart showing an example of a decoding process, an inverse quantization process, and an inverse transform process according to Embodiment 3. In Fig. 18, the processes that are substantially the same as those in Fig. 13 are given the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0278] If it is determined that an inverse secondary transform is to be performed (Yes in S202), the inverse quantization unit 204 calculates secondary coefficients by performing second inverse quantization, which is different from the first inverse quantization, on the decoded quantized coefficients (S221). The second inverse quantization is inverse quantization of the second quantization performed by the encoding device 100. In this embodiment, the second inverse quantization is unweighted inverse quantization that does not use a quantization matrix.

[0279] As described above, in this embodiment, the inverse quantization unit 204 switches between weighted inverse quantization and non-weighted inverse quantization based on whether or not the inverse secondary transform is applied to the block to be decoded.

[0280] [Effects, etc.] As described above, according to the encoding device 100 and decoding device 200 of this embodiment, unweighted quantization / inverse quantization can be used for the second quantization / second inverse quantization. Therefore, it is possible to omit the process of encoding or deriving the quantization matrix for the second quantization while preventing a deterioration in subjective image quality caused by using the first quantization matrix for the first quantization / first inverse quantization for the second quantization / second inverse quantization.

[0281] (Fourth embodiment) Next, a fourth embodiment will be described. This embodiment differs from the third embodiment in that each primary coefficient obtained by the linear transformation is multiplied by the corresponding component value of the weighting matrix before the transformation is performed. This embodiment will be specifically described below with reference to the drawings, focusing on the differences from the third embodiment.

[0282] [Transformation, quantization, and encoding processes in the encoding device] The transform processing, quantization processing, and encoding processing performed by the transform unit 106, quantization unit 108, and entropy encoding unit 110 of the encoding device 100 according to the fourth embodiment will be specifically described with reference to the drawings.

[0283] Fig. 19 is a flowchart showing an example of a transform process, a quantization process, and a coding process in Embodiment 4. Fig. 20 is a diagram for explaining an example of a secondary transform in Embodiment 4. In Fig. 19, processes that are substantially the same as those in Fig. 17 are assigned the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0284] If it is determined that a secondary conversion is to be performed (Yes in S102), the conversion unit 106 performs a secondary conversion from the primary coefficients to secondary coefficients (S130). Specifically, as shown in FIG. 20, in the secondary conversion, the conversion unit 106 calculates weighted primary coefficients by multiplying each primary coefficient by a corresponding component value of a weighting matrix (S131). The weighting matrix is a matrix for weighting the primary coefficients. Then, the conversion unit 106 converts the weighted primary coefficients into secondary coefficients (S132). This conversion is substantially the same as the secondary conversion in each of the above-described embodiments, except that weighted primary coefficients are converted instead of primary coefficients.

[0285] The weighting matrix may be derived from the first quantization matrix. In this case, for example, the component values of the weighting matrix and the first quantization matrix may have a monotonically decreasing relationship. Specifically, for example, each component value of the weighting matrix may be the reciprocal of the corresponding component value of the first quantization matrix. This allows the first quantization matrix for weighting the quantization steps to be converted into a weighting matrix for weighting the coefficients.

[0286] The weighting matrix may be included in the coded bitstream or may be predefined in a standard, and multiple weighting matrices may be defined in the standard. In this case, the weighting matrix may be selected from the multiple predefined weighting matrices based on a given profile or level, etc.

[0287] The quantization unit 108 calculates quantized secondary coefficients by performing second quantization, which is different from the first quantization, on the secondary coefficients (S121). In this embodiment, the second quantization is unweighted quantization that does not use a quantization matrix. That is, the second quantization divides each secondary coefficient by a quantization step common to the secondary coefficients of the block to be coded. In this case, the common quantization step may be derived by the quantization unit 108 from a quantization parameter for the block to be coded, for example.

[0288] [Decoding process, inverse quantization process, and inverse transform process in the decoding device] Next, the decoding process, the inverse quantization process, and the inverse transform process performed by the entropy decoding unit 202, the inverse quantization unit 204, and the inverse transform unit 206 of the decoding device 200 according to the fourth embodiment will be specifically described with reference to the drawings.

[0289] Fig. 21 is a flowchart showing an example of a decoding process, an inverse quantization process, and an inverse transform process in Embodiment 4. Fig. 22 is a diagram for explaining an example of an inverse secondary transform in Embodiment 4. In Fig. 21, processes that are substantially the same as those in Fig. 18 are assigned the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0290] If it is determined that an inverse secondary transform is to be performed (Yes in S202), the inverse quantization unit 204 calculates secondary coefficients by performing second inverse quantization, which is different from the first inverse quantization, on the decoded quantized coefficients (S221). The second inverse quantization is the inverse quantization of the second quantization performed by the encoding device 100. In this embodiment, the second inverse quantization is unweighted inverse quantization that does not use a quantization matrix. That is, as shown in FIG. 22 , the inverse quantization unit 204 calculates secondary coefficients by multiplying each quantized coefficient of the quantized coefficients of the block to be decoded by a quantization step that is common to the quantized coefficients of the block to be decoded. In this case, the common quantization step may be derived, for example, from a quantization parameter for the block to be decoded.

[0291] Next, the inverse transform unit 206 performs an inverse quadratic transform from the quadratic coefficients to linear coefficients (S230). Specifically, as shown in Fig. 22, the inverse transform unit 206 performs an inverse transform from the quadratic coefficients to weighted linear coefficients (S231). This inverse transform is the inverse transform of the transform from the weighted linear coefficients to quadratic coefficients (S132) performed by the encoding device 100.

[0292] Furthermore, the inverse transform unit 206 calculates the primary coefficients by dividing each of the weighted primary coefficients by the corresponding component value of the weight matrix (S232). This weight matrix is the same as the weight matrix used in the encoding device 100.

[0293] The weighting matrix may be derived from the first quantization matrix by the inverse quantization unit 204. In this case, for example, the component values of the weighting matrix and the first quantization matrix may have a monotonically decreasing relationship. For example, each component value of the weighting matrix may be the reciprocal of the corresponding component value of the first quantization matrix.

[0294] The weighting matrix may be included in the coded bitstream or may be predefined in a standard. Alternatively, multiple weighting matrices may be predefined in a standard. In this case, the weighting matrix may be selected from the multiple predefined weighting matrices based on a given profile or level, etc.

[0295] [Effects, etc.] As described above, the encoding device 100 according to this embodiment can calculate weighted primary coefficients by multiplying each primary coefficient by a corresponding component value of a weighting matrix. Furthermore, the decoding device 200 according to this embodiment can calculate primary coefficients by dividing each weighted primary coefficient by a corresponding component value of a weighting matrix. That is, the encoding device 100 and the decoding device 200 according to this embodiment can apply quantization-related weighting to primary coefficients before secondary transform. Therefore, when secondary transform / inverse secondary transform is applied, quantization / inverse quantization equivalent to weighted quantization / inverse quantization can be performed without preparing a new quantization matrix corresponding to the secondary space. As a result, it is possible to improve coding efficiency while suppressing degradation of subjective image quality.

[0296] Furthermore, according to the encoding device 100 and the decoding device 200 of this embodiment, the weighting matrix can be derived from the first quantization matrix, which reduces the amount of code required for the weighting matrix and improves the encoding efficiency while suppressing degradation of subjective image quality.

[0297] Furthermore, according to the encoding device 100 and the decoding device 200 according to this embodiment, a quantization step common to the secondary coefficients of the current block can be derived from the quantization parameter. Therefore, new information for the common quantization step does not need to be included in the encoded stream, and the amount of code for the common quantization step can be reduced.

[0298] (Embodiment 5) Next, a fifth embodiment will be described. This embodiment differs from the above-described embodiments in that, when a secondary transform is applied, quantization is performed on the primary coefficients before the secondary transform. Hereinafter, this embodiment will be specifically described with reference to the drawings, focusing on the differences from the above-described embodiments.

[0299] [Transformation, quantization, and encoding processes in the encoding device] The transform processing, quantization processing, and encoding processing performed by the transform unit 106, quantization unit 108, and entropy encoding unit 110 of the encoding device 100 according to the fifth embodiment will be specifically described with reference to the drawings.

[0300] Fig. 23 is a flowchart showing an example of a transform process, a quantization process, and a coding process according to Embodiment 5. In Fig. 23, the processes that are substantially the same as those in Fig. 11 are given the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0301] If it is determined that secondary transformation is not to be performed (No in S102), the quantization unit 108 calculates first quantized primary coefficients by performing first quantization on the primary coefficients (S141).

[0302] On the other hand, if it is determined that secondary transformation is to be performed (Yes in S102), the quantization unit 108 calculates second quantized primary coefficients by performing second quantization on the primary coefficients (S142). In this embodiment, the first quantization and the second quantization may be different from each other, as in the above-mentioned Embodiments 1 to 4, or may be the same. That is, in this embodiment, the same process may be performed using the same quantization matrix in the first quantization and the second quantization. Next, the transformation unit 106 performs secondary transformation from the second quantized primary coefficients to quantized secondary coefficients (S143).

[0303] The entropy coding unit 110 generates a coded bitstream by coding the first quantized primary coefficients or the quantized secondary coefficients (S106).

[0304] In this manner, in this embodiment, when a secondary transform is applied to a block to be coded, second quantization is performed before the secondary transform, i.e., second quantization is performed on the primary coefficients.

[0305] [Decoding process, inverse quantization process, and inverse transform process in the decoding device] Next, the decoding process, the inverse quantization process, and the inverse transform process performed by the entropy decoding unit 202, the inverse quantization unit 204, and the inverse transform unit 206 of the decoding device 200 according to the fifth embodiment will be specifically described with reference to the drawings.

[0306] Fig. 24 is a flowchart showing an example of a decoding process, an inverse quantization process, and an inverse transform process according to Embodiment 5. In Fig. 24, the same processes as those in Fig. 13 are denoted by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0307] If it is determined that the inverse secondary transform is not to be performed (No in S202), the inverse quantization unit 204 calculates primary coefficients by performing first inverse quantization on the decoded quantized coefficients (S241). The first inverse quantization is the inverse quantization of the first quantization performed by the encoding device 100.

[0308] On the other hand, if it is determined that an inverse secondary transform is to be performed (Yes in S202), the inverse transform unit 206 performs an inverse secondary transform from the decoded quantized coefficients to quantized primary coefficients (S242). The inverse secondary transform is an inverse transform of the secondary transform performed in the encoding device 100. Next, the inverse quantization unit 204 calculates primary coefficients by performing second inverse quantization on the quantized primary coefficients (S243). The second inverse quantization is the inverse quantization of the second quantization performed in the encoding device 100. Therefore, if the second quantization is the same as the first quantization, the second inverse quantization will also be the same as the first inverse quantization.

[0309] In this manner, in this embodiment, when an inverse secondary transform is applied to a block to be decoded, the second inverse quantization is performed after the inverse secondary transform, i.e., the second inverse quantization is performed on the quantized primary coefficients.

[0310] [Effects, etc.] As described above, according to the encoding device 100 and the decoding device 200 of this embodiment, quantization can be performed before secondary transformation, and therefore, if the secondary transformation process is lossless, the secondary transformation can be removed from the prediction process loop. This reduces the load on the processing pipeline. Furthermore, by performing quantization before secondary transformation, it is not necessary to separate the first quantization matrix and the second quantization matrix, which also simplifies the process.

[0311] (Variation) While the encoding device and the decoding device according to one or more aspects of the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects of the present disclosure.

[0312] For example, in the above-mentioned second embodiment, the derivation of the second quantization matrix is performed after the secondary transform or after the determination of the inverse secondary transform, but this is not limiting. The derivation of the second quantization matrix may be performed at any time after the first quantization matrix is obtained and before the second quantization / inverse quantization. For example, the second quantization matrix may be derived at the start of encoding or decoding of the current picture including the current block. In this case, the second quantization matrix does not need to be derived for each block.

[0313] Although the above embodiments have been described focusing on the encoding / decoding of one block to be encoded / decoded, the above-described transform process, quantization process and encoding process, or decoding process, inverse quantization process and inverse transform process can be applied to multiple blocks included in the picture to be encoded / decoded. In this case, a first quantization matrix and a second quantization matrix corresponding to a prediction mode (e.g., intra prediction or inter prediction), a type of pixel value (e.g., luma or chroma), a block size, or any combination thereof may be used.

[0314] In each of the above embodiments, the quantization switching process based on whether or not secondary transform is applied may be turned on / off at the slice level, tile level, CTU level, or CU level. Also, the on / off may be determined according to the frame type (I-frame, P-frame, B-frame) and / or prediction mode.

[0315] Furthermore, the quantization switching process based on whether or not the secondary transform is applied in each of the above embodiments may be performed on one or both of the luminance block and the chrominance block.

[0316] In the above embodiments, the determination as to whether or not to perform secondary transformation is made after the primary transformation, but this is not limiting. The determination as to whether or not to perform secondary transformation may be made in advance, before processing the block to be coded.

[0317] Furthermore, in the first embodiment, the first quantization matrix and the second quantization matrix do not always have to be different.

[0318] (Embodiment 6) In each of the above embodiments, each of the functional blocks can typically be realized by an MPU, memory, etc. Furthermore, the processing by each of the functional blocks is typically realized by a program execution unit such as a processor reading and executing software (programs) recorded on a recording medium such as a ROM. The software may be distributed by downloading, etc., or may be recorded on a recording medium such as a semiconductor memory and distributed. Of course, each functional block can also be realized by hardware (dedicated circuits).

[0319] Furthermore, the processing described in each embodiment may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. The processor that executes the program may be a single processor or multiple processors. That is, centralized processing or distributed processing may be performed.

[0320] The aspects of the present disclosure are not limited to the above examples, and various modifications are possible, and these modifications are also included within the scope of the aspects of the present disclosure.

[0321] Furthermore, here, we will explain application examples of the video coding method (image coding method) or video decoding method (image decoding method) shown in each of the above embodiments and a system using the same. The system is characterized by having an image coding device using the image coding method, an image decoding device using the image decoding method, and an image coding / decoding device that includes both. Other components of the system can be appropriately changed depending on the situation.

[0322] [Usage example] 25 is a diagram showing the overall configuration of a content supply system ex100 that provides a content distribution service. The area where communication services are provided is divided into cells of a desired size, and base stations ex106, ex107, ex108, ex109, and ex110, which are fixed wireless stations, are installed in each cell.

[0323] In this content supply system ex100, devices such as a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 are connected to the Internet ex101 via an Internet service provider ex102 or a communication network ex104 and base stations ex106 to ex110. The content supply system ex100 may be configured to connect a combination of any of the above elements. The devices may be connected to each other directly or indirectly via a telephone network or short-range wireless communication, without using the base stations ex106 to ex110, which are fixed wireless stations. Furthermore, a streaming server ex103 is connected to devices such as the computer ex111, the game console ex112, the camera ex113, the home appliance ex114, and the smartphone ex115 via the Internet ex101, etc. Furthermore, the streaming server ex103 is connected to a terminal in a hotspot on an airplane ex117, etc., via a satellite ex116.

[0324] Note that wireless access points, hotspots, etc. may be used instead of the base stations ex106 to ex110. Furthermore, the streaming server ex103 may be directly connected to the communication network ex104 without going through the Internet ex101 or the Internet service provider ex102, or may be directly connected to an airplane ex117 without going through a satellite ex116.

[0325] The camera ex113 is a device capable of taking still images and videos, such as a digital camera. The smartphone ex115 is a smartphone, mobile phone, or PHS (Personal Handyphone System) that is compatible with mobile communication systems generally known as 2G, 3G, 3.9G, 4G, and 5G.

[0326] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0327] In the content supply system ex100, a terminal having a photographing function is connected to a streaming server ex103 via a base station ex106 or the like, thereby enabling live streaming and the like. In live streaming, a terminal (such as a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, a smartphone ex115, or a terminal on an airplane ex117) performs the encoding process described in each of the above embodiments on still images or video content captured by a user using the terminal, multiplexes the video data obtained by encoding with audio data obtained by encoding audio corresponding to the video, and transmits the obtained data to the streaming server ex103. That is, each terminal functions as an image encoding device according to one aspect of the present disclosure.

[0328] Meanwhile, the streaming server ex103 streams the transmitted content data to the requesting client. The client is a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, a smartphone ex115, a terminal on an airplane ex117, or the like, which is capable of decoding the encoded data. Each device that receives the distributed data decodes and plays back the received data. That is, each device functions as an image decoding device according to one aspect of the present disclosure.

[0329] [Distributed processing] The streaming server ex103 may also be multiple servers or multiple computers that process, record, and distribute data in a distributed manner. For example, the streaming server ex103 may be implemented as a CDN (Content Delivery Network), where content distribution is achieved through a network connecting numerous edge servers distributed around the world. In a CDN, a physically nearby edge server is dynamically assigned depending on the client. Content is then cached and distributed to that edge server, thereby reducing delays. Furthermore, if an error occurs or communication conditions change due to increased traffic, processing can be distributed among multiple edge servers, the distribution entity can be switched to another edge server, or distribution can be continued by bypassing the affected network portion, thereby achieving high-speed and stable distribution.

[0330] In addition to the distributed processing of the distribution itself, the encoding of captured data can be performed on each device, on the server side, or shared among devices. For example, encoding generally involves two processing loops. The first loop detects the image complexity or code size for each frame or scene. The second loop maintains image quality while improving encoding efficiency. For example, a device can perform the first encoding process, and the server that receives the content can perform the second encoding process, thereby improving content quality and efficiency while reducing the processing load on each device. In this case, if there is a request for near-real-time reception and decoding, the data encoded by a device can be received and played back on another device, enabling more flexible real-time distribution.

[0331] As another example, the camera ex113 or the like extracts features from an image, compresses the data related to the features as metadata, and transmits the data to the server. The server performs compression according to the meaning of the image, for example, by determining the importance of an object from the features and switching the quantization precision accordingly. The feature data is particularly effective in improving the accuracy and efficiency of motion vector prediction when the server recompresses the image. Alternatively, the terminal may perform simple encoding such as VLC (variable length coding), and the server may perform encoding with a heavy processing load such as CABAC (context-adaptive binary arithmetic coding).

[0332] As another example, in a stadium, shopping mall, factory, etc., there may be multiple pieces of video data that have been shot by multiple terminals of almost the same scene. In this case, using the multiple terminals that shot the video and, as necessary, other terminals and servers that did not shoot the video, encoding processes are assigned to each of them, for example, in units of GOPs (Group of Pictures), pictures, or tiles obtained by dividing a picture, for distributed processing. This reduces delays and achieves better real-time performance.

[0333] Furthermore, since multiple pieces of video data are of nearly the same scene, the server may manage and / or instruct the video data shot by each terminal to be mutually referenced. Alternatively, the server may receive encoded data from each terminal and change the reference relationships between multiple pieces of data, or correct or replace the pictures themselves and re-encode them. This allows for the generation of streams with improved quality and efficiency for each piece of data.

[0334] The server may also perform transcoding to change the encoding format of the video data before distributing it. For example, the server may convert MPEG-based encoding to VP-based encoding, or convert H.264 to H.265.

[0335] In this way, the encoding process can be performed by a terminal or one or more servers. Therefore, although the following uses terms such as "server" or "terminal" to refer to the entity performing the process, some or all of the processing performed by the server may be performed by the terminal, and some or all of the processing performed by the terminal may be performed by the server. The same applies to the decoding process.

[0336] [3D, multi-angle] In recent years, there has been an increasing trend to integrate and use images or videos of different scenes or the same scene taken from different angles by multiple devices such as cameras ex113 and / or smartphones ex115 that are nearly synchronized with each other. The videos taken by each device are integrated based on the relative positional relationship between the devices obtained separately, or on areas where feature points included in the videos match.

[0337] The server may not only encode 2D video, but also encode still images automatically or at a time specified by the user based on scene analysis of the video and transmit them to the receiving terminal. Furthermore, if the server can acquire the relative positional relationship between the capturing terminals, it can generate a 3D shape of the scene based on not only the 2D video but also images of the same scene captured from different angles. The server may also separately encode 3D data generated by point clouds, or may select or reconstruct images to be transmitted to the receiving terminal from images captured by multiple terminals based on the results of recognizing or tracking people or objects using the 3D data.

[0338] In this way, users can enjoy scenes by selecting any video corresponding to each camera device, or can enjoy content in which video from any viewpoint is extracted from 3D data reconstructed using multiple images or videos. Furthermore, like the video, sound may also be collected from multiple different angles, and the server may multiplex and transmit sound from a specific angle or space in accordance with the video.

[0339] In recent years, content that associates the real world with a virtual world, such as Virtual Reality (VR) and Augmented Reality (AR), has also become popular. In the case of VR images, the server creates viewpoint images for the right eye and left eye, and may perform encoding that allows reference between the viewpoint images using Multi-View Coding (MVC) or the like, or may encode them as separate streams without mutual reference. When decoding the separate streams, it is preferable to play them in synchronization with each other so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0340] In the case of AR images, the server superimposes virtual object information in virtual space onto camera information in real space based on the 3D position or the user's viewpoint movement. The decoding device may acquire or store virtual object information and 3D data, generate a 2D image according to the user's viewpoint movement, and smoothly connect the images to create superimposed data. Alternatively, the decoding device may send the user's viewpoint movement to the server in addition to a request for virtual object information, and the server may create superimposed data based on the viewpoint movement received from the 3D data stored on the server, encode the superimposed data, and distribute it to the decoding device. Note that the superimposed data may also have an α value indicating transparency in addition to RGB, and the server may set the α value of parts other than the object created from the 3D data to 0, etc., to encode the parts in a transparent state. Alternatively, the server may generate data by setting a predetermined RGB value as the background, like a chromakey, and using the background color for parts other than the object.

[0341] Similarly, the decoding of distributed data may be performed by each client terminal, by the server, or by multiple terminals. For example, one terminal may first send a reception request to the server, and then other terminals may receive and decode content according to the request, after which the decoded signal is transmitted to a device with a display. By distributing the processing and selecting appropriate content regardless of the capabilities of the communication terminals themselves, high-quality data can be reproduced. As another example, large-sized image data may be received on a TV or other device, and only a portion of the picture, such as a tile into which the picture is divided, may be decoded and displayed on the viewer's personal device. This allows the viewer to share the overall picture while checking their own area of responsibility or an area of interest in more detail.

[0342] In the future, it is expected that content will be seamlessly received by switching the appropriate data for the current connection using delivery system standards such as MPEG-DASH in situations where multiple short-, medium-, or long-distance wireless communications are available, both indoors and outdoors. This will allow users to freely select and switch between decoding and display devices, such as their own devices, indoors and outdoors, in real time. Decoding can also be performed by switching between decoding and display devices based on user location information. This will enable users to display map information on the wall or ground of a neighboring building with an embedded display device while traveling to their destination. It is also possible to switch the bit rate of received data based on the accessibility of the encoded data on the network, such as if the encoded data is cached on a server that can be quickly accessed from the receiving device or copied to an edge server in a content delivery service.

[0343] [Scalable Coding] Content switching will be described using a scalable stream, shown in FIG. 26, compressed and encoded using the video encoding method described in each of the above embodiments. The server may have multiple streams with the same content but different qualities, but may also switch content by taking advantage of the temporal / spatial scalability achieved by encoding the stream in layers, as shown. In other words, the decoder determines which layer to decode based on internal factors such as performance and external factors such as communication bandwidth, allowing the decoder to freely switch between low-resolution and high-resolution content. For example, if a user wants to continue watching a video they were watching on their smartphone ex115 while on the go on a device such as an Internet TV after returning home, the device can simply decode the same stream up to different layers, thereby reducing the burden on the server.

[0344] Furthermore, in addition to the above-described scalability configuration in which pictures are coded for each layer and an enhancement layer exists above a base layer, the enhancement layer may include meta-information based on image statistics, etc., and the decoding side may generate high-quality content by super-resolving pictures in the base layer based on the meta-information. Super-resolution may mean either improving the signal-to-noise ratio at the same resolution or increasing the resolution. The meta-information may include information for specifying linear or nonlinear filter coefficients used in the super-resolution process, or information for specifying parameter values in the filter process, machine learning, or least-squares calculation used in the super-resolution process.

[0345] Alternatively, a picture may be divided into tiles or the like according to the meaning of objects in the image, and the decoding side may select tiles to decode and decode only a portion of the area. Furthermore, by storing the object's attributes (such as a person, a car, or a ball) and its position in the video (such as a coordinate position in the same image) as meta information, the decoding side can identify the position of a desired object based on the meta information and determine the tile containing the object. For example, as shown in FIG. 27, the meta information is stored using a data storage structure different from that of pixel data, such as an SEI message in HEVC. This meta information indicates, for example, the position, size, or color of the main object.

[0346] Furthermore, meta information may be stored in units consisting of multiple pictures, such as streams, sequences, or random access units, which allows the decoding side to obtain the time when a specific person appears in the video, and by combining this with information in units of pictures, it is possible to identify the picture in which the object exists and the position of the object within the picture.

[0347] [Webpage optimization] FIG. 28 is a diagram showing an example of a web page display screen on a computer ex111 or the like. FIG. 29 is a diagram showing an example of a web page display screen on a smartphone ex115 or the like. As shown in FIGS. 28 and 29, a web page may include multiple link images that are links to image content, and the appearance of the web page may differ depending on the device used to view the page. When multiple link images are visible on the screen, the display device (decoding device) may display a still image or I-picture contained in each content as a link image, display a video such as a GIF animation using multiple still images or I-pictures, or receive only the base layer and decode and display the video until the user explicitly selects a link image, or until the link image approaches the center of the screen or until the entire link image is within the screen.

[0348] When a link image is selected by a user, the display device decodes the base layer with the highest priority. If the HTML constituting the web page contains information indicating that the content is scalable, the display device may decode up to the enhancement layer. To ensure real-time performance, before a selection is made or when the communication bandwidth is very limited, the display device decodes and displays only forward-referenced pictures (I-pictures, P-pictures, and forward-reference-only B-pictures), thereby reducing the delay between the decoding time of the first picture and the display time (the delay from the start of content decoding to the start of display). Alternatively, the display device may intentionally ignore the picture reference relationships and roughly decode all B-pictures and P-pictures using forward reference, and then perform normal decoding as the number of received pictures increases over time.

[0349] [Autonomous driving] Furthermore, when transmitting and receiving still image or video data such as 2D or 3D map information for automatic driving or driving assistance of a vehicle, the receiving terminal may receive weather or construction information as meta information in addition to image data belonging to one or more layers, and may associate and decode these. Note that the meta information may belong to a layer, or may simply be multiplexed with the image data.

[0350] In this case, since a vehicle, drone, airplane, etc. including a receiving terminal moves, the receiving terminal can realize seamless reception and decoding while switching between base stations ex106 to ex110 by transmitting the location information of the receiving terminal at the time of a reception request. Also, the receiving terminal can dynamically switch how much meta information to receive or how much to update map information depending on the user's selection, user situation, or communication bandwidth status.

[0351] In this way, in the content supply system ex100, the client can receive, decode, and play back the encoded information sent by the user in real time.

[0352] [Distribution of personal content] Furthermore, the content supply system ex100 allows not only high-quality, long-duration content from video distribution companies, but also unicast or multicast distribution of low-quality, short-duration content from individuals. It is expected that such personal content will continue to increase in the future. To improve the quality of personal content, the server may perform editing before encoding. This can be achieved, for example, with the following configuration.

[0353] During shooting, either in real time or after accumulating the footage, the server performs recognition processing such as detecting shooting errors, scene search, semantic analysis, and object detection from the original image or encoded data. Based on the recognition results, the server manually or automatically corrects out-of-focus or camera shake, deletes less important scenes (e.g., scenes with lower brightness or out-of-focus compared to other pictures), emphasizes object edges, changes color, and performs other editing. The server then encodes the edited data based on the editing results. It is also known that viewing rates decrease if the shooting time is too long. Therefore, the server may automatically clip not only less important scenes as described above but also scenes with little movement, based on the image processing results, so that the content falls within a specific time range depending on the shooting time. Alternatively, the server may generate and encode a digest based on the results of the semantic analysis of the scene.

[0354] In some cases, personal content may contain content that infringes copyright, moral rights, or portrait rights, or may cause the scope of sharing to exceed the intended scope, resulting in inconvenience to individuals. Therefore, for example, the server may intentionally defocus images of people's faces on the periphery of the screen or the interior of a house before encoding. The server may also recognize whether the image to be encoded contains the face of a person other than a pre-registered person, and if so, perform processing such as blurring the face. Alternatively, as pre- or post-processing before encoding, the user may specify a person or background area they wish to modify in the image for copyright or other reasons, and the server may replace the specified area with another image or blur the focus. For a person, the server may track the person in the video and replace the image of the face.

[0355] Furthermore, because viewing personal content with small data volumes requires real-time performance, the decoding device first receives the base layer as a top priority, and then decodes and plays it back, depending on the bandwidth. The decoding device may also receive an enhancement layer during this time, and if the content is played back more than twice, such as when playback is looped, it may play back high-quality video, including the enhancement layer. A stream that has undergone scalable encoding in this way can provide an experience in which the video appears rough when not selected or when viewing begins, but gradually becomes smoother and the image quality improves. In addition to scalable encoding, a similar experience can also be provided by configuring a single stream consisting of a rough stream played the first time and a second stream that is encoded with reference to the first video.

[0356] [Other use cases] Furthermore, these encoding or decoding processes are generally performed by the LSIex500 possessed by each terminal. The LSIex500 may be a single chip or may be configured with multiple chips. It is also possible to incorporate video encoding or decoding software into some kind of recording medium (such as a CD-ROM, flexible disk, or hard disk) that can be read by the computer ex111, and perform the encoding or decoding process using that software. Furthermore, if the smartphone ex115 is equipped with a camera, video data captured by the camera may be transmitted. This video data is data that has been encoded by the LSIex500 possessed by the smartphone ex115.

[0357] The LSIex500 may be configured to download and activate application software. In this case, the terminal first determines whether it supports the content encoding method or has the capability to execute a specific service. If the terminal does not support the content encoding method or does not have the capability to execute a specific service, the terminal downloads the codec or application software and then acquires and plays the content.

[0358] Furthermore, at least one of the video encoding device (image encoding device) or video decoding device (image decoding device) of each of the above embodiments can be incorporated into a digital broadcasting system, not limited to the content supply system ex100 via the Internet ex101. Since multiplexed data in which video and audio are multiplexed is transmitted and received over broadcast radio waves using a satellite or the like, the content supply system ex100 is more suited to multicast than the content supply system ex100, which is more suited to unicast, but similar applications are possible with regard to encoding and decoding processes.

[0359] [Hardware configuration] FIG. 30 is a diagram illustrating a smartphone ex115. FIG. 31 is a diagram illustrating an example configuration of the smartphone ex115. The smartphone ex115 includes an antenna ex450 for transmitting and receiving radio waves to and from the base station ex110, a camera unit ex465 capable of capturing video and still images, and a display unit ex458 for displaying video captured by the camera unit ex465 and decoded data of the video and other data received by the antenna ex450. The smartphone ex115 further includes an operation unit ex466 such as a touch panel, an audio output unit ex457 such as a speaker for outputting voice or sound, an audio input unit ex456 such as a microphone for inputting voice, a memory unit ex467 capable of storing encoded data or decoded data such as captured video or still images, recorded voice, received video or still images, and email, and a slot unit ex464 that serves as an interface with a SIM ex468 for identifying users and authenticating access to various data, including networks. In addition, an external memory may be used instead of the memory unit ex467.

[0360] In addition, a main control unit ex460 that comprehensively controls the display unit ex458 and operation unit ex466, etc., is connected to a power supply circuit unit ex461, an operation input control unit ex462, a video signal processing unit ex455, a camera interface unit ex463, a display control unit ex459, a modulation / demodulation unit ex452, a multiplexing / separation unit ex453, an audio signal processing unit ex454, a slot unit ex464, and a memory unit ex467 via a bus ex470.

[0361] When the power key is turned on by a user, the power supply circuit unit ex461 supplies power from the battery pack to each unit, thereby starting up the smartphone ex115 into an operational state.

[0362] The smartphone ex115 processes calls, data communications, and other communications under the control of a main control unit ex460, which includes a CPU, ROM, RAM, and the like. During calls, the audio signal collected by the audio input unit ex456 is converted into a digital audio signal by the audio signal processing unit ex454, which then undergoes spectrum spread processing by the modulation / demodulation unit ex452, digital-to-analog conversion processing and frequency conversion processing by the transmission / reception unit ex451, and then transmitted via the antenna ex450. The received data is amplified, frequency-converted, and analog-to-digital converted, then subjected to spectrum despreading processing by the modulation / demodulation unit ex452, and converted into an analog audio signal by the audio signal processing unit ex454, which then outputs the amplified data from the audio output unit ex457. During data communications mode, text, still images, or video data is sent to the main control unit ex460 via the operation input control unit ex462 by operating the operation unit ex466, etc., of the main unit, and similar transmission and reception processing is performed. When transmitting video, still images, or video and audio in the data communication mode, the video signal processing unit ex455 compression-encodes the video signal stored in the memory unit ex467 or the video signal input from the camera unit ex465 using the video encoding method described in each of the above embodiments, and sends the encoded video data to the multiplexing / demultiplexing unit ex453. The audio signal processing unit ex454 also encodes the audio signal picked up by the audio input unit ex456 while the camera unit ex465 is capturing video, still images, etc., and sends the encoded audio data to the multiplexing / demultiplexing unit ex453. The multiplexing / demultiplexing unit ex453 multiplexes the encoded video data and encoded audio data using a predetermined method, and modulates and converts the data in the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451 before transmitting the data via the antenna ex450.

[0363] When receiving video attached to an email or chat, or video linked to a web page, etc., the multiplexed data received via the antenna ex450 is decoded by the multiplexing / separation unit ex453, which separates the multiplexed data into a video data bitstream and an audio data bitstream. The multiplexing / separation unit ex453 then supplies the encoded video data to the video signal processing unit ex455 via the synchronization bus ex470, and supplies the encoded audio data to the audio signal processing unit ex454. The video signal processing unit ex455 decodes the video signal using a video decoding method corresponding to the video encoding method described in each of the above embodiments, and displays the video or still image included in the linked video file on the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 decodes the audio signal, and the audio is output from the audio output unit ex457. Note that with the widespread use of real-time streaming, audio playback may be socially inappropriate depending on the user's circumstances. Therefore, a configuration that initially plays only the video data without playing the audio signal is desirable. The audio may be played in synchronization only when the user performs an operation such as clicking on the video data.

[0364] Although the smartphone ex115 has been used as an example, three types of implementation are possible for the terminal: a transmitting / receiving terminal having both an encoder and a decoder, a transmitting terminal having only an encoder, and a receiving terminal having only a decoder. Furthermore, in the digital broadcasting system, multiplexed data in which audio data and the like are multiplexed onto video data is received or transmitted, but the multiplexed data may also include text data related to the video in addition to audio data, or the video data itself may be received or transmitted instead of the multiplexed data.

[0365] While the main control unit ex460, which includes a CPU, controls the encoding and decoding processes, devices often also include a GPU. Therefore, a configuration is possible in which a memory shared by the CPU and GPU, or a memory with addresses managed for common use, is used to take advantage of the GPU's performance and process a large area at once. This shortens encoding time, ensures real-time performance, and achieves low latency. It is particularly efficient to perform motion estimation, deblocking filtering, SAO (Sample Adaptive Offset), and transformation and quantization processes at a picture level or other unit in the GPU rather than the CPU. [Industrial Applicability]

[0366] The present disclosure is applicable to, for example, television receivers, digital video recorders, car navigation systems, mobile phones, digital cameras, digital video cameras, and the like. [Explanation of symbols]

[0367] 100 Encoding device 102 Division 104 Subtraction section 106 Conversion unit 108 Quantization section 110 Entropy coding unit 112, 204 Inverse quantization section 114, 206 Inverse conversion unit 116, 208 Addition section 118, 210 block memory 120, 212 Loop filter section 122, 214 frame memory 124, 216 Intra prediction section 126, 218 Inter prediction section 128, 220 Predictive control section 200 Decryption Device 202 Entropy Decoding Unit

Claims

1. 1. A decoding device for decoding an image block, comprising: The circuit and a memory; The circuit uses the memory to: obtaining quantized primary coefficients or quantized secondary coefficients of the image block from a bitstream; determining whether to apply an inverse quadratic transform to the image block; (i) when the inverse secondary transform is not applied, calculating primary coefficients by performing a first inverse quantization on the quantized primary coefficients; (ii) when the inverse secondary transform is applied, calculating secondary coefficients by performing a second inverse quantization different from the first inverse quantization on the quantized secondary coefficients, performing an inverse secondary transform from the secondary coefficients to primary coefficients, and performing an inverse primary transform from the primary coefficients to residuals of the image block. Decryption device.

2. The circuit and a memory connected to the circuit; The circuit, in operation, generating information for causing a decoding device to execute an inverse secondary transform in the inverse transform process; including said information in a bitstream; The inverse transformation process is Quantized primary coefficients or quantized secondary coefficients of an image block are obtained from the bitstream; if the information indicates that an inverse secondary transform is not applied to the image block, a first inverse quantization is performed on the quantized primary coefficients to calculate primary coefficients; if the information indicates that the inverse secondary transform is to be applied to the image block, secondary coefficients are calculated by performing a second inverse quantization different from the first inverse quantization on the quantized secondary coefficients, primary coefficients are calculated by performing an inverse secondary transform on the secondary coefficients, and residuals of the image block are calculated by performing an inverse primary transform on the primary coefficients. Bitstream generator.

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