Image processing method, and device for same
The present invention discloses a method for encoding/decoding a video signal and an apparatus for the method. More specifically, a method for decoding a video signal comprises generating a residual block of a current block by performing entropy decoding on the video signal; if size of the current block is smaller than a predetermined first size, parsing a transform skip flag which indicates whether a transform skip is applied to the current block; determining whether to parse a primary transform flag which indicates whether a primary transform is applied to the current block; if it is determined to parse the primary transform flag, parsing the primary transform flag; and if the primary transform flag indicates that a primary transform is applied to the current block, generating a primary inverse transformed transform block of the current block by performing a primary inverse transform to the residual block.
1. An apparatus for decoding a video signal, comprising:
a memory configured to store the video signal; and
a processor coupled with the memory,
wherein the processor is configured to:
parse a transform skip flag specifying whether a transform is applied to the current block based on a size of the current block being smaller than a predetermined first size;
obtain an index specifying one of a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction; and
generate an inverse transformed transform block of the current block by performing an inverse transform to a residual block based on the transform kernel combination specified by the index,
wherein for obtaining the index, the processor is further configured to:
check a value of an index flag related to parsing the index, based on the transform skip flag being 0; and
derive the index specifying the transform kernel combination as DCT-2 for the transform kernels in the horizontal and vertical directions based on the value of the index flag being 0.
2. The apparatus of claim 1 , wherein for parsing the index, the processor is further configured to:
check whether a non-zero transform coefficient exists in the current block,
parse the index based on a determination from the checking result that the non-zero transform coefficient exists in the current block.
3. The apparatus of claim 1 , wherein the predetermined first size is configured differently based on a slice of the current block.
4. The apparatus of claim 1 , wherein a different transform kernel combination is applied to each of intra-prediction mode groups.
5. The apparatus of claim 4 , wherein for applying the different transform kernel combination, the processor is further configured to:
group intra-prediction modes into prediction mode groups; and
determine a transform kernel combination to be applied for each of the prediction mode groups.
6. The apparatus of claim 5 , wherein a number of the intra-prediction modes is 35 or 67.
7. The apparatus of claim 1 , wherein the transform kernel combination is determined further based on an intra-prediction mode.
8. The apparatus of claim 7 , wherein a number of the transform kernel combinations is four.
9. An apparatus for encoding a video signal, comprising:
a memory configured to store the video signal; and
a processor coupled with the memory,
wherein the processor is configured to:
generate a transform skip flag specifying whether a transform is applied to the current block based on a size of the current block being smaller than a predetermined first size;
generate an index specifying one among a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction;
perform the transform to a residual block based on the transform kernel combination specified by the index to obtain a transformed block of the current block; and
perform quantization and entropy encoding on the transformed block,
wherein for generating the index, the processor is further configured to:
generate an index flag related to generating the index, based on the transform skip flag being 0; and
derive the index specifying the transform kernel combination as DCT-2 for the transform kernels in the horizontal and vertical directions without generating the index, based on the value of the index flag being 0.
10. A non-transitory computer-readable storage medium for storing one or more instructions executable by one or more processors, the one or more instructions controlling a video data processing device to:
generate a transform skip flag specifying whether a transform is applied to the current block based on a size of the current block being smaller than a predetermined first size;
generate an index specifying one among a plurality of transform kernel combinations to be applied to the current block based on the transform skip flag, each transform kernel combination being composed of a transform kernel in a horizontal direction and a transform kernel in a vertical direction;
perform the transform to a residual block based on the transform kernel combination specified by the index to obtain a transformed block of the current block; and
perform quantization and entropy encoding on the transformed block,
wherein for generating the index, the one or more instructions further control the video data processing device to:
generate an index flag related to generating the index, based on the transform skip flag being 0; and
derive the index specifying the transform kernel combination as DCT-2 for the transform kernels in the horizontal and vertical directions without generating the index, based on the value of the index flag being 0.