Image data encoding/decoding method and apparatus
Disclosed are methods and apparatuses for decoding an image. A method includes receiving a bitstream obtained by encoding the image; dividing a first coding block into a plurality of second coding blocks; generating a prediction block of a second coding block based on syntax information obtained from the bitstream; and reconstructing the second coding block based on the prediction block and a residual block of the second coding block, the residual block being obtained by performing a dequantization and an inverse-transform on quantized transform coefficients from the bitstream. The first coding block has a recursive division structure. The first coding block is divided based on at least one of a quad tree division, a binary tree division or a triple tree division.
1. A method of decoding a 360-degree image performed by an image decoding apparatus, the method comprising:
receiving a bitstream in which the 360-degree image is encoded, the bitstream including data of an expanded 2-dimensional image, the expanded 2-dimensional image including a 2-dimensional image and a predetermined expansion region, and the 2-dimensional image being projected from an image with a 3-dimensional projection structure and including one or more faces;
generating a predicted image by performing prediction based on information on the prediction included in the bitstream; and
reconstructing the expanded 2-dimensional image based on the predicted image and a residual image,
wherein sample values of the expansion region are determined by changing sample values of the face for the sample values of the expansion region,
wherein a size of the expansion region is determined based on size information obtained from the bitstream,
wherein the predicted image is generated by performing inter prediction, and
wherein the 3-dimensional projection structure is selectively determined based on identification information, among a plurality of pre-defined 3-dimensional projection structures including a first 3-dimensional projection structure and a second 3-dimensional projection structure, the identification information being obtained from the bitstream,
wherein existence information indicating existence of the expansion region is obtained from the bitstream,
wherein the size information for the expansion region is obtained from the bitstream in case the existence information indicates that the expansion region exists,
wherein, based on a projection format for the 3-dimensional projection structure is a first projection format, the size of the expansion region is determined based on first width information for specifying a width of the expansion region on a left side of the face and second width information for specifying a width of the expansion region on a right side of the face, both the first width information and the second width information being obtained from the bitstream,
wherein, based on a projection format for the 3-dimensional projection structure is a second projection format, the size of the expansion region is determined based on first width information for specifying a width of the expansion region on a left side of the face, second width information for specifying a width of the expansion region on a right side of the face, third height information for specifying a height of the expansion region on a top side of the face and fourth height information for specifying a height of the expansion region on a bottom side of the face, all of the first width information, the second width information, the third height information and the fourth height information being obtained from the bitstream.
2. A method of encoding a 360-degree image performed by an image encoding apparatus, 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 expanded 2-dimensional image including the 2-dimensional image and a predetermined expansion region;
generating a predicted image by performing prediction, information on the prediction being encoded into the bitstream; and
encoding data of the expanded 2-dimensional image into the bitstream based on the predicted image and a residual image,
wherein sample values of the expansion region are determined by changing sample values of the face for the sample values of the expansion region,
wherein size information on a size of the expansion region is encoded into the bitstream,
wherein the predicted image is generated by performing inter prediction, and
wherein the 3-dimensional projection structure is selectively determined among a plurality of 3-dimensional projection structures including a first 3-dimensional projection structure and a second 3-dimensional projection structure, the determined 3-dimensional projection structure being encoded into the bitstream based on identification information,
wherein existence information indicating existence of the expansion region is encoded into the bitstream,
wherein the size information for the expansion region is encoded into the bitstream in case the existence information indicates that the expansion region exists,
wherein, based on a projection format for the 3-dimensional projection structure is a first projection format, the size of the expansion region is encoded based on first width information for specifying a width of the expansion region on a left side of the face and second width information for specifying a width of the expansion region on a right side of the face, both the first width information and the second width information being encoded into the bitstream,
wherein, based on a projection format for the 3-dimensional projection structure is a second projection format, the size of the expansion region is encoded based on first width information for specifying a width of the expansion region on a left side of the face, second width information for specifying a width of the expansion region on a right side of the face, third height information for specifying a height of the expansion region on a top side of the face and fourth height information for specifying a height of the expansion region on a bottom side of the face, all of the first width information, the second width information, the third height information and the fourth height information being encoded into the bitstream.
3. A method of transmitting a bitstream performed by a transmitting apparatus, comprising:
transmitting the bitstream to an image decoding apparatus,
wherein the bitstream is generated by performing
obtaining a 2-dimensional image projected from an image with a 3-dimensional projection structure and including at least one face;
obtaining an expanded 2-dimensional image including the 2-dimensional image and a predetermined expansion region;
generating a predicted image by performing prediction, information on the prediction being encoded into the bitstream; and
encoding data of the expanded 2-dimensional image into the bitstream based on the predicted image and a residual image,
wherein sample values of the expansion region are determined by changing sample values of the face for the sample values of the expansion region,
wherein size information on a size of the expansion region is encoded into the bitstream,
wherein the predicted image is generated by performing inter prediction, and
wherein the 3-dimensional projection structure is selectively determined among a plurality of 3-dimensional projection structures including a first 3-dimensional projection structure and a second 3-dimensional projection structure, the determined 3-dimensional projection structure being encoded into the bitstream based on identification information,
wherein existence information indicating existence of the expansion region is encoded into the bitstream,
wherein the size information for the expansion region is encoded into the bitstream in case the existence information indicates that the expansion region exists,
wherein, based on a projection format for the 3-dimensional projection structure is a first projection format, the size of the expansion region is encoded based on first width information for specifying a width of the expansion region on a left side of the face and second width information for specifying a width of the expansion region on a right side of the face, both the first width information and the second width information being encoded into the bitstream,
wherein, based on a projection format for the 3-dimensional projection structure is a second projection format, the size of the expansion region is encoded based on first width information for specifying a width of the expansion region on a left side of the face, second width information for specifying a width of the expansion region on a right side of the face, third height information for specifying a height of the expansion region on a top side of the face and fourth height information for specifying a height of the expansion region on a bottom side of the face, all of the first width information, the second width information, the third height information and the fourth height information being encoded into the bitstream.