Image decoding method and device in accordance with block split structure in image coding system

A video encoding method performed by an encoding device, comprising:

• splitting a first target block to first sub-blocks;
• splitting a second target block, which is one of the first sub blocks, to second sub-blocks;
• generating and encoding first split information for the first target block and Multiple Partitioning Tree (MPT) split information for the second target block,
• wherein the second sub-blocks are non-square blocks,
• wherein the MPT split information includes a MPT split flag, MPT split direction information and MPT split type information for the second target block,
• wherein the MPT split flag informs whether the second target block is split to the second sub-blocks that are the non-square blocks,
• wherein the MPT split direction information informs a split direction of the second target block,
• wherein the MPT split type information informs a number of the second sub-blocks to which the second target block is split,
• wherein, based on a size of the second target block being 2N×2N and the number of the second sub-blocks informed by the MPT split type information being equal to 3 and the split direction of the second target block informed by the MPT split direction information being a vertical direction, the second target block is split to an N×2N size second sub-block and N/2×2N size second sub-blocks,
• wherein, based on a size of the second target block being 2N×2N and the number of the second sub-blocks informed by the MPT split type information being equal to 3 and the split direction of the second target block informed by the MPT split direction information being a horizontal direction, the second target block is split to a 2N×N size second sub-block and 2N×N/2 size second sub-blocks,
• wherein information on MPT structure including a 2 partitions type and a 3 partitions type is obtained through a first High Level Syntax (HLS) and a second HLS,
• wherein the first HLS is a Sequence Parameter Set (SPS) and the second HLS is a lower syntax structure of the SPS,
• wherein the 2 partitions type is a type in which a block is split to 2 sub-blocks,
• wherein the 3 partitions type is a type in which a block is split to 3 sub-blocks,
• wherein the information on the MPT structure includes information on maximum depth in the MPT structure for an intra slice, information on maximum block size in the MPT structure for the intra slice, information on maximum depth in the MPT structure for an inter slice and information on maximum block size in the MPT structure for the inter slice,
• wherein the maximum depth in the MPT structure for the intra slice, the maximum block size in the MPT structure for the intra slice, the maximum depth in the MPT structure for the inter slice, the maximum block size in the MPT structure for the inter slice are derived based on the information on the MPT structure, and
• wherein a process of the splitting the second target block to the second sub-blocks is performed based on the maximum depth in the MPT structure for the intra slice, the maximum block size in the MPT structure for the intra slice, the maximum depth in the MPT structure for the inter slice, the maximum block size in the MPT structure for the inter slice.

A method of transmitting a bitstream, the method comprising:

• generating the bitstream including first split information and Multiple Partitioning Tree (MPT) split information, based on splitting a first target block to first sub-blocks,
• splitting a second target block, which is one of the first sub blocks, to second sub-block, and
• generating and encoding the first split information for the first target block and the MPT split information for the second target block;
• transmitting the bitstream,
• wherein the second sub-blocks are non-square blocks,
• wherein the MPT split information includes a MPT split flag, MPT split direction information and MPT split type information for the second target block,
• wherein the MPT split flag informs whether the second target block is split to the second sub-blocks that are the non-square blocks,
• wherein the MPT split direction information informs a split direction of the second target block,
• wherein the MPT split type information informs a number of the second sub-blocks to which the second target block is split,
• wherein, based on a size of the second target block being 2N×2N and the number of the second sub-blocks informed by the MPT split type information being equal to 3 and the split direction of the second target block informed by the MPT split direction information being a vertical direction, the second target block is split to an N×2N size second sub-block and N/2×2N size second sub-blocks,
• wherein, based on a size of the second target block being 2N×2N and the number of the second sub-blocks informed by the MPT split type information being equal to 3 and the split direction of the second target block informed by the MPT split direction information being a horizontal direction, the second target block is split to a 2N×N size second sub-block and 2N×N/2 size second sub-blocks,
• wherein information on MPT structure including a 2 partitions type and a 3 partitions type is obtained through a first High Level Syntax (HLS) and a second HLS,
• wherein the first HLS is a Sequence Parameter Set (SPS) and the second HLS is a lower syntax structure of the SPS,
• wherein the 2 partitions type is a type in which a block is split to 2 sub-blocks,
• wherein the 3 partitions type is a type in which a block is split to 3 sub-blocks,
• wherein the information on the MPT structure includes information on maximum depth in the MPT structure for an intra slice, information on maximum block size in the MPT structure for the intra slice, information on maximum depth in the MPT structure for an inter slice and information on maximum block size in the MPT structure for the inter slice,
• wherein the maximum depth in the MPT structure for the intra slice, the maximum block size in the MPT structure for the intra slice, the maximum depth in the MPT structure for the inter slice, the maximum block size in the MPT structure for the inter slice are derived based on the information on the MPT structure, and
• wherein a process of the splitting the second target block to the second sub-blocks is performed based on the maximum depth in the MPT structure for the intra slice, the maximum block size in the MPT structure for the intra slice, the maximum depth in the MPT structure for the inter slice, the maximum block size in the MPT structure for the inter slice.