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, so as to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format. Here, generating the prediction image includes: checking, from the syntax information, prediction mode accuracy for a current block to be decoded; determining whether the checked prediction mode accuracy corresponds to most probable mode (MPM) information obtained from the syntax information; and when the checked prediction mode accuracy does not correspond to the MPM information, reconfiguring the MPM information according to the prediction mode accuracy for the current block.
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 adding a residual image for the extended 2-dimensional image to a predicted image for the extended 2-dimensional image, the predicted image being obtained by intra prediction and the residual image being obtained by performing inverse quantization for residual information,
wherein a size of the extension region to be padded is determined based on first width information of the extension region on a left side of the face and second width information of the extension region on a right side of the face, both the first width information and the second width information being obtained from the bitstream, 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 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.
4. 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.
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. 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 a residual image for the extended 2-dimensional image into a bitstream in which the 360-degree image is encoded, the residual image being obtained by subtracting a predicted image for the extended 2-dimensional image from the extended 2-dimensional image, the predicted image being obtained by intra prediction and the residual image being encoded by performing quantization for the residual image,
wherein a size of the extension region to be padded is encoded based on first width information of the extension region on a left side of the face and second width information of the extension region on a right side of the face, both the first width information and the second width information being encoded into the bitstream, and
wherein sample values of the extension region are determined differently according to a padding method selected from a plurality of padding methods.
7. 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 a residual image for the extended 2-dimensional image into a bitstream in which the 360-degree image is encoded, the residual image being obtained by subtracting a predicted image for the extended 2-dimensional image from the extended 2-dimensional image, the predicted image being obtained by intra prediction and the residual image being encoded by performing quantization for the residual image,
wherein a size of the extension region to be padded is encoded based on first width information of the extension region on a left side of the face and second width information of the extension region on a right side of the face, both the first width information and the second width information being encoded into the bitstream, and
wherein sample values of the extension region are determined differently according to a padding method selected from a plurality of padding methods.