Image decoding method and apparatus relying on intra prediction in image coding system
According to the present disclosure, a video decoding method performed by a video decoding device includes parsing remaining intra prediction mode information for a current block, deriving neighboring samples of the current block, deriving MPM list including MPM candidates of the current block, deriving an intra prediction mode of the current block based on the remaining intra prediction mode information, wherein the intra prediction mode is one of remaining intra prediction modes excluding the MPM candidates, deriving a prediction sample of the current block based on the intra prediction mode and the neighboring samples, and deriving a reconstructed picture based on the prediction sample, wherein the remaining intra prediction mode information is coded through a truncated binary (TB) binarization process, and wherein a binarization parameter for the TB binarization process is 60.
1. An image decoding method performed by a decoding device, the method comprising:
parsing remaining intra prediction mode information and residual information for a current block;
deriving neighboring samples of the current block;
deriving most probable mode (MPM) list including MPM candidates of the current block;
rearranging remaining intra prediction modes excluding the MPM candidates based on a pre-configured order;
deriving an intra prediction mode of the current block based on the remaining intra prediction mode information and the rearranged remaining intra prediction modes, wherein the intra prediction mode is an intra prediction mode indicated by the remaining intra prediction mode information among the rearranged remaining intra prediction modes;
deriving a prediction sample of the current block based on the intra prediction mode and the neighboring samples;
deriving a residual sample of the current block based on the residual information; and
deriving a reconstructed picture based on the prediction sample and the residual sample,
wherein the remaining intra prediction mode information is bypass coded based on a truncated binary (TB) binarization process, and
wherein a binarization parameter for the TB binarization process is 60,
wherein the remaining intra prediction mode information equal to one of 0 to 2 is binarized with a binarization value of 5 bits, and
wherein the remaining intra prediction mode information equal to one of 3 to 60 is binarized with a binarization value of 6 bits,
based on a value of the remaining intra prediction mode information being N, an N+1th intra prediction mode among the rearranged remaining intra prediction modes is derived as the intra prediction mode of the current block, and
the pre-configured order is as below:
{0, 1, 50, 18, 49, 10, 12, 19, 11, 34, 2, 17, 54, 33, 46, 51, 35, 15, 13, 45, 22, 14, 66, 21, 47, 48, 23, 53, 58, 16, 42, 20, 24, 44, 26, 43, 55, 52, 37, 29, 39, 41, 25, 9, 38, 56, 30, 36, 32, 28, 62, 27, 40, 8, 3, 7, 57, 6, 31, 4, 65, 64, 5, 59, 60, 61, 63}.
2. The image decoding method of claim 1 , wherein an MPM flag of the current block is obtained, and
wherein the MPM flag is a flag related to whether the intra prediction mode of the current block is derived from the MPM candidates.
3. The image decoding method of claim 2 , when the MPM flag indicates that the intra prediction mode of the current block is not derived from the MPM candidates, the intra prediction mode of the current block is derived based on the remaining intra prediction mode information.
4. The image decoding method of claim 2 , wherein when the MPM flag indicates that the intra prediction mode of the current block is derived from the MPM candidates, a MPM index for the current block is parsed, and the intra prediction mode of the current block is derived based on the MPM index, and
wherein the MPM index is coded based on a truncated rice (TR) binarization process, and
wherein a rice parameter for the TR binarization process is 0.
5. The image decoding method of claim 1 , wherein a specific value is derived based on the binarization parameter for the TB binarization process, and
wherein the specific value is the number of values of the remaining intra prediction mode information binarized with a binarization value of k bits, and
wherein when the binarization parameter for the TB binarization process is 60, the k bits is derived as 5 bits.
6. The image decoding method of claim 5 , wherein the specific value and the k are derived based on Equation below,
n
=
C
Max
+
1
k
=
Floor
(
Log
2
(
n
)
)
so
that
2
k
<=
n
<
2
k
+
1
u
=
2
k
+
1
-
n
wherein, c Max represents the binarization parameter, and u represents the specific value.
7. The image decoding method of claim 6 , wherein the binarization parameter is a number of total intra prediction modes minus a number of MPM candidates, and minus 1.
8. The image decoding method of claim 1 , wherein the neighboring samples include an upper left corner neighboring sample, upper neighboring samples and left neighboring samples of the current block,
when a size of the current block is W×H and x component of top left sample position of the current block is 0 and y component is 0, the left neighboring samples are p[−1][0] to p[−1][2H−1], the upper left corner neighboring sample is p[−1][−1] and the upper neighboring samples are p[0][−1] to p[2W−1][−1].
9. An image encoding method performed by an encoding device, the method comprising:
deriving neighboring samples of the current block;
deriving most probable mode (MPM) list including MPM candidates of the current block;
rearranging remaining intra prediction modes excluding the MPM candidates based on a pre-configured order;
determining an intra prediction mode of the current block based on the rearranged remaining intra prediction modes, wherein the intra prediction mode is one of the rearranged remaining intra prediction modes;
deriving a prediction sample of the current block based on the intra prediction mode and the neighboring samples;
deriving a residual sample of the current block based on the prediction sample; and
encoding image information including remaining intra prediction mode information and residual information for the current block,
wherein the remaining intra prediction mode information represents the intra prediction mode of the current block,
wherein the remaining intra prediction mode information is bypass coded based on a truncated binary (TB) binarization process, and
wherein a binarization parameter for the TB binarization process is 60,
wherein the remaining intra prediction mode information equal to one of 0 to 2 is binarized with a binarization value of 5 bits, and
wherein the remaining intra prediction mode information equal to one of 3 to 60 is binarized with a binarization value of 6 bits,
based on a value of the remaining intra prediction mode information being N, the remaining intra prediction mode information indicates an N+1th intra prediction mode among the rearranged remaining intra prediction modes as the intra prediction mode of the current block, and
the pre-configured order is as below:
{0, 1, 50, 18, 49, 10, 12, 19, 11, 34, 2, 17, 54, 33, 46, 51, 35, 15, 13, 45, 22, 14, 66, 21, 47, 48, 23, 53, 58, 16, 42, 20, 24, 44, 26, 43, 55, 52, 37, 29, 39, 41, 25, 9, 38, 56, 30, 36, 32, 28, 62, 27, 40, 8, 3, 7, 57, 6, 31, 4, 65, 64, 5, 59, 60, 61, 63}.
10. The image encoding method of claim 9 , wherein an MPM flag of the current block is encoded, wherein the MPM flag is a flag related to whether the intra prediction mode of the current block is derived from the MPM candidates, and
wherein when the MPM flag represents that the intra prediction mode of the current block is derived from the MPM candidates, a MPM index for the current block is encoded, and the intra prediction mode of the current block is derived based on the MPM index, and
wherein the MPM index is coded based on a truncated rice (TR) binarization process, and
wherein a rice parameter for the TR binarization process is 0.
11. The image encoding method of claim 10 , wherein a specific value is derived based on the binarization parameter for the TB binarization process, and
wherein the specific value is the number of values of the remaining intra prediction mode information binarized with a binarization value of k bits, and
wherein when the binarization parameter for the TB binarization process is 60, the k bits is derived as 5 bits.
12. The image encoding method of claim 11 , wherein the specific value and the k are derived based on Equation below,
n
=
C
Max
+
1
k
=
Floor
(
Log
2
(
n
)
)
so
that
2
k
<=
n
<
2
k
+
1
u
=
2
k
+
1
-
n
wherein, c Max represents the binarization parameter, and u represents the specific value.
13. A non-transitory computer-readable storage medium storing a bitstream generated by a method, the method comprising:
deriving neighboring samples of the current block;
deriving most probable mode (MPM) list including MPM candidates of the current block;
rearranging remaining intra prediction modes excluding the MPM candidates based on a pre-configured order;
determining an intra prediction mode of the current block based on the rearranged remaining intra prediction modes, wherein the intra prediction mode is one of the rearranged remaining intra prediction modes;
deriving a prediction sample of the current block based on the intra prediction mode and the neighboring samples;
deriving a residual sample of the current block based on the prediction sample;
encoding image information including remaining intra prediction mode information and residual information for the current block; and
generating the bitstream including the image information,
wherein the remaining intra prediction mode information represents the intra prediction mode of the current block,
wherein the remaining intra prediction mode information is bypass coded based on a truncated binary (TB) binarization process, and
wherein a binarization parameter for the TB binarization process is 60,
wherein the remaining intra prediction mode information equal to one of 0 to 2 is binarized with a binarization value of 5 bits, and
wherein the remaining intra prediction mode information equal to one of 3 to 60 is binarized with a binarization value of 6 bits,
based on a value of the remaining intra prediction mode information being N, the remaining intra prediction mode information indicates an N+1th intra prediction mode among the rearranged remaining intra prediction modes as the intra prediction mode of the current block, and
the pre-configured order is as below:
{0, 1, 50, 18, 49, 10, 12, 19, 11, 34, 2, 17, 54, 33, 46, 51, 35, 15, 13, 45, 22, 14, 66, 21, 47, 48, 23, 53, 58, 16, 42, 20, 24, 44, 26, 43, 55, 52, 37, 29, 39, 41, 25, 9, 38, 56, 30, 36, 32, 28, 62, 27, 40, 8, 3, 7, 57, 6, 31, 4, 65, 64, 5, 59, 60, 61, 63}.