Video decoding apparatus and video coding apparatus
Video coding and decoding apparatuses that can enhance coding efficiency are provided. A video decoding apparatus according to an aspect of the present invention is a video decoding apparatus including a parameter decoder configured to decode, from coded data, syntax (mts_idx) of a target block. The parameter decoder decodes mts_idx depending on a block size, a LAST position, and a non-zero coefficient position of the target block. The parameter decoder determines whether to decode mts_idx, using a threshold for the LAST position. The threshold is larger in a case that the block size is equal to or larger than a prescribed size than in a case that the block size is smaller than the prescribed size.
1 . A video decoding apparatus for decoding a multiple transform selection (MTS) parameter in coded data, the video decoding apparatus comprising:
a decoder that decodes a syntax element for the MTS, wherein
the syntax element indicates a transform matrix to be applied to a target block,
a maximum value used to decode the syntax element is determined according to whether or not a prediction mode of the target block is an intra prediction mode and according to a parameter,
in a case of the intra prediction mode, the maximum value used to decode the syntax element is determined from at least two or more different maximum values based on a value of the parameter, and
in a case of an inter prediction mode, a maximum value used to decode the syntax element is a fixed value.
2 . The video decoding apparatus according to claim 1 , wherein the at least two or more different maximum values include (i) the maximum value equal to one, (ii) the maximum value equal to four, and (iii) the maximum value equal to six.
3 . A video coding apparatus for coding a multiple transform selection (MTS) parameter in data, the video coding apparatus comprising:
a coder that codes a syntax element for the MTS, wherein
the syntax element indicates a transform matrix to be applied to a target block,
a maximum value used to code the syntax element is determined according to whether or not a prediction mode of the target block is an intra prediction mode and according to a parameter,
in a case of the intra prediction mode, the maximum value used to decode the syntax element is determined from at least two or more different maximum values based on a value of the parameter, and
in a case of an inter prediction mode, a maximum value used to decode the syntax element is a fixed value.
4 . A video encoding method for encoding a multiple transform selection (MTS) parameter, the video encoding method including:
encoding a syntax element for the MTS, wherein
the syntax element indicates a transform matrix to be applied to a target block,
a maximum value used to encode the syntax element is determined according to whether or not a prediction mode of the target block is an intra prediction mode and according to a parameter,
in a case of the intra prediction mode, the maximum value used to encode the syntax element is determined from at least two or more different maximum values based on a value of the parameter, and, and
in a case of an inter prediction mode, a maximum value used to encode the syntax element is a fixed value.