Image encoding/decoding method and device
An image encoding/decoding method of the present invention constructs a merge candidate list of a current block, derives motion information of the current block on the basis of the merge candidate list and a merge candidate index, and performs inter prediction on the current block on the basis of the derived motion information, wherein the merge candidate list can improve encoding/decoding efficiency by adaptively determining a plurality of merge candidates on the basis of the position or size of a merge estimation region (MER) to which the current block belongs.
1. A method of decoding an image signal with a decoding apparatus, comprising:
deriving, with the decoding apparatus, an intra prediction mode of a current block based on intra prediction information obtained from a bitstream including the image signal; and
providing, with the decoding apparatus, a decoded image signal by generating, based on a first inverse-transform, residual samples of the current block from dequantized transform coefficients,
wherein, in response to a case in which a second inverse-transform is additionally performed between a dequantization and the first inverse-transform, the residual samples of the current block are generated by performing the first inverse-transform on M transform coefficients resulting from performing the second inverse-transform, the M transform coefficients being generated by performing the second inverse-transform on N dequantized transform coefficients of a partial region within the current block,
wherein a value of M is less than or equal to a product of a width and a height of the current block and a value of N is less than the value of M,
wherein when the width and the height of the current block is equal to 4, respectively, the values of M and N are determined to be 16 and 8, respectively,
wherein when the width and the height of the current block is equal to 8, respectively, the value of M is determined to be 48 which is less than the product of the width and the height of the current block and the value of N is determined to be 8,
wherein the second inverse-transform is performed only when the current block is a block encoded by intra prediction,
wherein pre-defined intra prediction modes are divided into a plurality of groups,
wherein one of a plurality of pre-defined transform sets is mapped for each of the plurality of groups of the pre-defined intra prediction modes, and
wherein a transform set mapped to a group to which the derived intra prediction mode belongs is used for the second inverse-transform.
2. The method of claim 1 , wherein the second inverse-transform is performed only when a size of the current block is greater than or equal to a threshold size pre-defined in the decoding apparatus, and
wherein the threshold size is representative of 4 or 8.
3. The method of claim 1 , wherein a transform matrix of the current block is determined, based on index information signaled from the bitstream, and
wherein the index information specifies one of a plurality of transform matrixes belonging to the transform set for the second inverse-transform.
4. The method of claim 3 , wherein the index information is signaled only when a non-zero transform coefficient does not exist in a remaining region other than the partial region within the current block.
5. A method of encoding an image signal with an encoding apparatus, comprising:
determining, with the encoding apparatus, an intra prediction mode of a current block; and
generating, with the encoding apparatus, based on a first transform, transform coefficients of the current block from residual samples of the current block in the image signal,
wherein in response to a case in which a second transform is additionally performed between the first transform and a quantization, N transform coefficients of a partial region within the current block are generated by performing the second transform on M first transform coefficients resulting from performing the first transform on the residual samples of the current block,
wherein a value of M is less than or equal to a product of a width and a height of the current block and a value of N is less than the value of M,
wherein when the width and the height of the current block is equal to 4, respectively, the values of M and N are determined to be 16 and 8, respectively,
wherein when the width and the height of the current block is equal to 8, respectively, the value of M is determined to be 48 which is less than the product of the width and the height of the current block and the value of N is determined to be 8,
wherein the second transform is performed only when the current block is a block encoded by intra prediction,
wherein pre-defined intra prediction modes are divided into a plurality of groups,
wherein one of a plurality of pre-defined transform sets is mapped for each of the plurality of groups of the pre-defined intra prediction modes, and
wherein a transform set mapped to a group to which the determined intra prediction mode belongs is used for the second transform.
6. A non-transitory computer-readable medium for storing data associated with an image signal, comprising:
a data stream stored in the non-transitory computer-readable medium, the data stream comprising intra prediction information and transform coefficients of a current block,
wherein an intra prediction mode of the current block is derived based on the intra prediction information,
wherein a first inverse-transform are performed on the transform coefficients of the current block to generate residual samples of the current block,
wherein in response to a case in which a second inverse-transform is additionally performed between a dequantization and the first inverse-transform, the residual samples of the current block are generated by performing the first inverse-transform on M transform coefficients resulting from performing the second inverse-transform, the M transform coefficients being generated by performing the second inverse-transform on N dequantized transform coefficients of a partial region within the current block,
wherein a value of M is less than or equal to a product of a width and a height of the current block and a value of N is less than the value of M,
wherein when the width and the height of the current block is equal to 4, respectively, the values of M and N are determined to be 16 and 8, respectively,
wherein when the width and the height of the current block is equal to 8, respectively, the value of M is determined to be 48 which is less than the product of the width and the height of the current block and the value of N is determined to be 8,
wherein the second inverse-transform is performed only when the current block is a block encoded by intra prediction,
wherein pre-defined intra prediction modes are divided into a plurality of groups,
wherein one of a plurality of pre-defined transform sets is mapped for each of the plurality of groups of the pre-defined intra prediction modes, and
wherein a transform set mapped to a group to which the derived intra prediction mode belongs is used for the second inverse-transform.