Image data encoding/decoding method and apparatus
A method for decoding a 360-degree image includes: receiving a bitstream obtained by encoding a 360-degree image; generating a prediction image by making reference to syntax information obtained from the received bitstream; combining the generated prediction image with a residual image obtained by dequantizing and inverse-transforming the bitstream to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format. Generating the prediction image includes: obtaining, from motion information in the syntax information, a motion vector candidate group including a motion vector of a block adjacent to a current block to be decoded; deriving a prediction motion vector from the motion vector candidate group based on selection information extracted from the motion information; and determining a prediction block for the current block to be decoded, using a final motion vector derived by adding the prediction motion vector to a differential motion vector extracted from the motion information.
1. A method of decoding a current image with a decoding apparatus, comprising:
receiving a bitstream in which the current image is encoded;
dividing the current image based on a plurality of division types pre-defined in the decoding apparatus; and
decoding the divided current image based on coding information extracted from the bitstream,
wherein the dividing the current image comprises:
dividing the current image into a plurality of division units based on at least one of horizontal lines or vertical lines,
wherein at least one of the horizontal lines has a length shorter than a width of the current image or at least one of the vertical lines has a length shorter than a height of the current image,
wherein the current image is divided, based on first division information extracted from the bitstream, into the plurality of division units,
wherein the first division information includes information on a number of the division units belonging to the current image, information on positions of the division units, and information on a size of the division units, and
wherein the information on the size of the division units includes a flag specifying whether all of the division units belonging to the current image have a same width and height.
2. The method of claim 1 , wherein the information on the positions of the division units, and the information on the size of the division units is encoded in units of a default coding unit, and
wherein information on the default coding unit is extracted from at least one of a sequence parameter set or a picture parameter set in the bitstream.
3. The method of claim 1 , wherein if a predetermined condition is satisfied, one of the division units is allowed to refer to a temporal division unit, otherwise, the one of the division units is not allowed to refer to the temporal division unit, and
wherein the temporal division unit belongs to a pre-reconstructed image other than current image and has a different position from the one of the division units.
4. The method of claim 1 , wherein dividing the current image into
the plurality of division units comprises assigning index information for identifying each of the division units, and
wherein the index information is extracted from at least one of a sequence parameter set, a picture parameter set, or a slice header in the bitstream.
5. The method of claim 1 , wherein the dividing the current image comprises:
dividing the current image into a plurality of slices, the slice being representative of a rectangular region specified based on second division information, and
wherein the second division information includes information on a number of the slices belonging to the current image, information on positions of the slices, and information on a size of the slices.
6. The method of claim 5 , wherein dividing the current image into the plurality of slices is performed after dividing the current image into a plurality of tiles.
7. The method of claim 6 , wherein dividing the current image into the plurality of slices is performed based on a result of dividing the current image into the plurality of tiles.
8. The method of claim 1 , wherein the coding information includes information on whether an in-loop filtering is enabled, and
wherein the information on whether the in-loop filtering is enabled is signaled for each of the division unit, the tile, and the slice.
9. A method of encoding a current image with an encoding apparatus, comprising:
dividing the current image based on a plurality of division types pre-defined in the encoding apparatus;
encoding the divided current image to determine coding information of the current image; and
generating a bitstream including the coding information,
wherein the dividing the current image comprises:
dividing the current image into a plurality of division units based on at least one of horizontal lines or vertical lines, and
wherein at least one of the horizontal lines has a length shorter than a width of the current image or at least one of the vertical lines has a length shorter than a height of the current image,
wherein the current image is divided, based on first division information encoded into the bitstream, into the plurality of division units,
wherein the first division information includes information on a number of the division units belonging to the current image, information on positions of the division units, and information on a size of the division units, and
wherein the information or the size of the division units includes a flag specifying whether all of the division units belonging to the current image have a same width and height.
10. A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processor to:
dividing a current image based on a plurality of division types pre-defined in a decoding apparatus; and
decoding the divided current image based on coding information extracted from a bitstream,
wherein the dividing the current image comprises:
dividing the current image into a plurality of division units based on at least one of horizontal lines or vertical lines, and
wherein at least one of the horizontal lines has a length shorter than a width of the current image or at least one of the vertical lines has a length shorter than a height of the current image,
wherein the current image is divided, based on first division information encoded into the bitstream, into the plurality of division units,
wherein the first division information includes information on a number of the division units belonging to the current image, information on positions of the division units, and information on a size of the division units, and
wherein the information or the size of the division units includes a flag specifying whether all of the division units belonging to the current image have a same width and height.
11. A non-transitory computer-readable recording medium storing a bitstream generated by a method of encoding a current image with an encoding apparatus, the method comprising:
dividing the current image based on a plurality of division types pre-defined in the encoding apparatus;
encoding the divided current image to determine coding information of the current image; and
generating a bitstream including the coding information,
wherein the dividing the current image comprises:
dividing the current image into a plurality of division units based on at least one of horizontal lines or vertical lines, and
wherein at least one of the horizontal lines has a length shorter than a width of the current image or at least one of the vertical lines has a length shorter than a height of the current image,
wherein the current image is divided, based on first division information encoded into the bitstream, into the plurality of division units,
wherein the first division information includes information on a number of the division units belonging to the current image, information on positions of the division units, and information on a size of the division units, and
wherein the information on the size of the division units includes a flag specifying whether all of the division units belonging to the current image have a same width and height.