Image coding method and device using transform skip flag
A method for decoding an image according to the present document includes obtaining prediction mode information and residual related information from a bitstream, deriving prediction samples of a current block by performing prediction based on the prediction mode information, deriving residual samples of the current block based on the residual related information, and generating reconstruction samples of the current block based on the prediction samples and the residual samples, and the residual related information includes a transform skip flag based on a size of the current block and a maximum transform skip size, the transform skip flag represents whether a transform skip is applied to the current block, and information about the maximum transform skip size is obtained from the bitstream.
1. An apparatus for image decoding, the apparatus comprising:
memory storing instructions that, when executed, cause one or more processors to perform operations comprising:
obtaining prediction mode information and residual related information from a bitstream,
deriving prediction mode for a current block based on the prediction mode information,
deriving prediction samples of the current block based on the prediction mode, deriving residual samples of the current block based on the residual related information, and
generating reconstruction samples of the current block based on the prediction samples and the residual samples,
wherein the prediction mode information is related to whether inter prediction or intra prediction is applied to the current block,
wherein the residual related information comprises a transform skip flag based on a size of the current block and a maximum transform skip size, wherein the transform skip flag is related to whether a transform skip is applied to the current block,
wherein information about the maximum transform skip size is obtained from the bitstream,
wherein the information about the maximum transform skip size includes a log 2_transform_skip_max_size_minus2 syntax element, and
wherein the maximum transform skip size is derived based on the following equation,
MaxTsSize
=
1
<<
(log
2
_transform
_skip
_max
_size
_minus2
+
2
)
,
where the MaxTsSize represents the maximum transform skip size, and the log 2_transform_skip_max_size_minus2 represents a value of the log 2_transform_skip_max_size_minus2 syntax element.
2. The apparatus of claim 1 , wherein the maximum transform skip size is derived as one of candidate sizes comprising 4, 8, 16, or 32.
3. The apparatus of claim 1 , wherein the value of the log 2_transform_skip_max_size_minus2 syntax element is represented by one of candidate values of 0 to 3.
4. The apparatus of claim 1 , wherein the information about the maximum transform skip size is comprised in a high level syntax.
5. The apparatus of claim 4 , wherein the high level syntax is one of a sequence parameter set syntax or a picture parameter set syntax.
6. The apparatus of claim 5 , wherein the one of the picture parameter set or the sequence parameter set comprises a transform skip enabled flag related to whether the transform skip is enabled or not, and
wherein the information about the maximum transform skip size is included in the one of the picture parameter set or the sequence parameter set based on a value of the transform skip flag being equal to 1.
7. An apparatus for image encoding, the apparatus comprising:
memory storing instructions that, when executed, cause one or more processors to perform operations comprising:
deriving prediction samples by performing prediction on a current block,
deriving residual samples for the current block, generating prediction mode information related to the prediction on the current block,
generating residual related information related to the residual samples for the current block, and
encoding image information comprising the prediction mode information and the residual related information,
wherein the prediction mode information is related to whether inter prediction or intra prediction is applied to the current block,
wherein the residual related information comprises a transform skip flag based on a size of the current block and a maximum transform skip size,
wherein the transform skip flag is related to whether a transform skip is applied to the current block,
wherein the image information comprises information about the maximum transform skip size,
wherein the information about the maximum transform skip size comprises a log 2_transform_skip_max_size_minus2 syntax element, and
wherein the maximum transform skip size is represented based on the following equation,
MaxTsSize
=
1
<<
(log
2
_transform
_skip
_max
_size
_minus2
+
2
)
,
where the MaxTsSize represents the maximum transform skip size, and the log 2_transform_skip_max_size_minus2 represents a value of the log 2_transform_skip_max_size_minus2 syntax element.
8. The apparatus of claim 7 , wherein the maximum transform skip size is represented as one of candidate sizes including 4, 8, 16, or 32.
9. The apparatus of claim 7 , wherein the value of the log 2_transform_skip_max_size_minus2 syntax element is represented by one of candidate values of 0 to 3.
10. The apparatus of claim 7 , wherein the information about the maximum transform skip size is comprised in a high level syntax.
11. The apparatus of claim 10 , wherein the high level syntax is one of a sequence parameter set syntax or a picture parameter set syntax.
12. The apparatus of claim 11 , wherein the one of the picture parameter set or the sequence parameter set comprises a transform skip enabled flag related to whether the transform skip is enabled or not, and
wherein the information about the maximum transform skip size is included in one of the picture parameter set or the sequence parameter set based on a value of the transform skip flag being equal to 1.
13. An apparatus for transmitting image data, the apparatus comprising:
memory storing instructions that, when executed, cause one or more processors to perform operations comprising:
generating a bitstream, wherein the bitstream is generated by:
deriving prediction samples by performing prediction on a current block,
deriving residual samples for the current block,
generating prediction mode information related to the prediction on the current block,
generating residual related information related to the residual samples for the current block, and
generating the bitstream by encoding image information comprising the prediction mode information and the residual related information, and transmitting the image data comprising the bitstream,
wherein the prediction mode information is related to whether inter prediction or intra prediction is applied to the current block,
wherein the residual related information comprises a transform skip flag based on a size of the current block and a maximum transform skip size,
wherein the transform skip flag is related to whether a transform skip is applied to the current block,
wherein the image information comprises information about the maximum transform skip size,
wherein the information about the maximum transform skip size comprises a log 2_transform_skip_max_size_minus2 syntax element, and
wherein the maximum transform skip size is represented based on the following equation,
MaxTsSize
=
1
<<
(log
2
_transform
_skip
_max
_size
_minus2
+
2
)
,
where the MaxTsSize represents the maximum transform skip size, and the log 2_transform_skip_max_size_minus2 represents a value of the log 2_transform_skip_max_size_minus2 syntax element.
14. The apparatus of claim 13 , wherein the maximum transform skip size is derived as one of candidate sizes comprising 4, 8, 16, or 32.
15. The apparatus of claim 13 , wherein the value of the log 2_transform_skip_max_size_minus2 syntax element is represented by one of candidate values of 0 to 3.
16. The apparatus of claim 13 , wherein the information about the maximum transform skip size is included in a high level syntax.
17. The apparatus of claim 16 , wherein the high level syntax is one of a sequence parameter set syntax or a picture parameter set syntax.
18. The apparatus of claim 17 , wherein the one of the picture parameter set or the sequence parameter set comprises a transform skip enabled flag related to whether the transform skip is enabled or not, and
wherein the information about the maximum transform skip size is included in the one of the picture parameter set or the sequence parameter set based on a value of the transform skip flag being equal to 1.