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 for decoding a 360-degree image, the method comprising:
receiving a bitstream in which the 360-degree image is encoded, the bitstream including data of an extended 2-dimensional image, the extended 2-dimensional image including a 2-dimensional image and a predetermined extension region, and the 2-dimensional image being projected from an image with a 3-dimensional projection structure and including at least one face; and
reconstructing the extended 2-dimensional image by predicting a current block included in the 2-dimensional image using a prediction method selected among a plurality of prediction methods including an intra prediction and an inter prediction,
wherein a size of the extension region is determined based on size information indicating a size of the extension region, one or more syntax elements for the size information being obtained from the bitstream,
wherein the number of syntax elements for the size information is determined differently based on a projection format for the 3-dimensional projection structure, the projection format being one among a plurality of projection formats including an ERP format in which the 360-degree image is projected in a two-dimensional plane and a CMP format in which the 360-degree image is projected in a cube, and
wherein sample values of the extension region are determined differently according to a padding method selected from a plurality of padding methods.
2. The method of claim 1 , wherein the padding method is selected from the plurality of padding methods based on selection information obtained from the bitstream.
3. The method of claim 2 , wherein the first padding method horizontally copies the sample values of the face to the sample values of the extension region.
4. The method of claim 1 , wherein the plurality of padding methods includes at least a first padding method which copies sample values of the face for the sample values of the extension region.
5. The method of claim 1 , wherein the plurality of padding methods includes at least a second padding method which changes sample values of the face for the sample values of the extension region.
6. The method of claim 1 , wherein the size information includes at least one of first size information of the extension region on a left side of the face or second size information of the extension region on a right side of the face.
7. A method for encoding a 360-degree image, the method comprising:
obtaining a 2-dimensional image projected from an image with a 3-dimensional projection structure and including at least one face;
obtaining an extended 2-dimensional image including the 2-dimensional image and a predetermined extension region; and
encoding data of the extended 2-dimensional image into a bitstream in which the 360-degree image is encoded by predicting a current block included in the 2-dimensional image using a prediction method selected among a plurality of prediction methods including an intra prediction and an inter prediction,
wherein a size of the extension region is encoded based on size information indicating a size of the extension region, one or more syntax elements for the size information being encoded into the bitstream,
wherein the number of syntax elements for the size information is determined differently based on a projection format for the 3-dimensional projection structure, the projection format being one among a plurality of projection formats including an ERP format in which the 360-degree image is projected in a two-dimensional plane and a CMP format in which the 360-degree image is projected in a cube, and
wherein sample values of the extension region are determined differently according to a padding method selected from a plurality of padding methods.
8. A non-transitory computer-readable recording medium storing a bitstream that is generated by a method for encoding a 360-degree image, the method comprising:
obtaining a 2-dimensional image projected from an image with a 3-dimensional projection structure and including at least one face;
obtaining an extended 2-dimensional image including the 2-dimensional image and a predetermined extension region; and
encoding data of the extended 2-dimensional image into a bitstream in which the 360-degree image is encoded by predicting a current block included in the 2-dimensional image using a prediction method selected among a plurality of prediction methods including an intra prediction and an inter prediction,
wherein a size of the extension region is encoded based on size information indicating a size of the extension region, one or more syntax elements for the size information being encoded into the bitstream,
wherein the number of syntax elements for the size information is determined differently based on a projection format for the 3-dimensional projection structure, the projection format being one among a plurality of projection formats including an ERP format in which the 360-degree image is projected in a two-dimensional plane and a CMP format in which the 360-degree image is projected in a cube, and
wherein sample values of the extension region are determined differently according to a padding method selected from a plurality of padding methods.