Method and apparatus of encoding/decoding image data based on tree structure-based block division
Disclosed are methods and apparatuses for image data encoding/decoding. A method of decoding an image includes receiving a bitstream in which the image is encoded; obtaining index information for specifying a block division type of a current block in the image; and determining the block division type of the current block from a candidate group pre-defined in the decoding apparatus. The candidate group includes a plurality of candidate division types, including at least one of a non-division, a first quad-division, a second quad-division, a binary-division or a triple-division. The method also includes dividing the current block into a plurality of sub-blocks; and decoding each of the sub-blocks with reference to syntax information obtained from the bitstream.
1. A method of decoding an image with a decoding apparatus, comprising:
receiving a bitstream in which the image is encoded;
obtaining, from the bitstream, a single index for specifying a block division type of a current block in the image;
determining, based on the single index, the block division type of the current block from a candidate group pre-defined in the decoding apparatus,
wherein the single index is used to select one candidate division types among a plurality of candidate division types included in the candidate group,
wherein the plurality of candidate division types include a non-division, a first quad-division, a second quad-division, a binary-division and a triple-division,
wherein the first quad-division is representative of dividing, based on one horizontal line and one vertical line, one coding block into four coding blocks, the second quad-division is representative of dividing, based on three horizontal lines or three vertical lines, one coding block into four coding blocks, the binary-division is representative of dividing one coding block into two coding blocks, and the triple-division is representative of dividing one coding block into three coding blocks,
wherein the binary-division includes a horizontal binary-division and a vertical binary-division, and
wherein the bitstream includes at least one among a first flag specifying whether to perform the horizontal binary-division and a second flag specifying whether to perform the vertical binary-division, the first flag being different from the second flag;
dividing, based on the determined block division type, the current block into a plurality of sub-blocks; and
decoding each of the sub-blocks with reference to syntax information obtained from the bitstream,
wherein two coding blocks among the three coding blocks obtained by the triple-division have the same size each other and the remaining coding block among the three coding blocks has a size different from the size of the two coding blocks, and
wherein the four coding blocks obtained by the first quad-divisional have the same size each other.
2. The method of claim 1 , wherein the current block is set equal to a largest coding block or is set a block resulting from dividing the largest coding block,
wherein a size of the largest coding block is variably determined based on information on the largest coding block,
wherein the information on the largest coding block is signaled from the bitstream.
3. The method of claim 2 , wherein the size of the largest coding block is set equal to 128×128 or 64×64 according to the information on the largest coding block.
4. The method of claim 1 , wherein a number of the candidate division types available for the current block is different dependent on at least one of a size of the current block or a shape of the current block.
5. A method of encoding an image with an encoding apparatus, comprising:
determining a block division type of a current block in the image from a candidate group pre-defined in the encoding apparatus;
encoding single index for specifying the determined block division type of the current block;
encoding each of sub-blocks resulting from dividing the current block based on the determined block division type,
wherein the single index is used to select one candidate division types among a plurality of candidate division types included in the candidate group,
wherein the plurality of candidate division types include a non-division, a first quad-division, a second quad-division, a binary-division and a triple-division,
wherein the first quad-division is representative of dividing, based on one horizontal line and one vertical line, one coding block into four coding blocks, the second quad-division is representative of dividing, based on three horizontal lines or three vertical lines, one coding block into four coding blocks, the binary-division is representative of dividing one coding block into two coding blocks, and the triple-division is representative of dividing one coding block into three coding blocks,
wherein the binary-division includes a horizontal binary-division and a vertical binary-division,
wherein two coding blocks among the three coding blocks obtained by the triple-division have the same size each other and the remaining coding block among the three coding blocks has a size different from the size of the two coding blocks, and
wherein the four coding blocks obtained by the first quad-divisional have the same size each other; and
encoding at least one among a first flag specifying whether to perform the horizontal binary-division and a second flag specifying whether to perform the vertical binary-division, the first flag being different from the second flag.
6. A method of transmitting a bitstream comprising:
determining a block division type of a current block in the image from a candidate group pre-defined in the encoding apparatus;
encoding single index for specifying the determined block division type of the current block;
encoding each of sub-blocks resulting from dividing the current block based on the determined block division type to generate the bitstream;
transmitting the bitstream,
wherein the single index is used to select one candidate division types among a plurality of candidate division types included in the candidate group,
wherein the plurality of candidate division types include a non-division, a first quad-division, a second quad-division, a binary-division and a triple-division,
wherein the first quad-division is representative of dividing, based on one horizontal line and one vertical line, one coding block into four coding blocks, the second quad-division is representative of dividing, based on three horizontal lines or three vertical lines, one coding block into four coding blocks, the binary-division is representative of dividing one coding block into two coding blocks, and the triple-division is representative of dividing one coding block into three coding blocks,
wherein the binary-division includes a horizontal binary-division and a vertical binary-division,
wherein two coding blocks among the three coding blocks obtained by the triple-division have the same size each other and the remaining coding block among the three coding blocks has a size different from the size of the two coding blocks, and
wherein the four coding blocks obtained by the first quad-divisional have the same size each other; and
encoding at least one among a first flag specifying whether to perform the horizontal binary-division and a second flag specifying whether to perform the vertical binary-division, the first flag being different from the second flag.