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. A method for decoding a video signal, comprising:
generating, by a processor, a residual block of a current block by performing entropy decoding and inverse quantization on the video signal;
parsing, by the processor, 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;
obtaining, by the processor, an index that specifies 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
generating, by the processor, an inverse transformed transform block of the current block by performing an inverse transform to the residual block based on the transform kernel combination specified by the index;
wherein obtaining the index comprises:
checking a value of an index flag related to parsing the index based on the transform skip flag being 0,
parsing the index based on the value of the index flag being 1, and
deriving 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 method of claim 1 , wherein parsing the index is further based on the current block being a luma block.
3. The method of claim 1 , wherein parsing the index further comprises:
checking whether a non-zero transform coefficient exists in the current block, and
parsing the index based on a determination from the checking result that the non-zero transform coefficient exists in the current block.
4. The method of claim 1 , wherein the predetermined first size is configured differently based on a slice of the current block.
5. The method of claim 1 , wherein a different transform kernel combination is applied to each of intra-prediction mode groups.
6. The method of claim 5 , wherein applying the different transform kernel combination comprises:
grouping intra-prediction modes into prediction mode groups; and
determining a transform kernel combination to be applied for each of the prediction mode groups.
7. The method of claim 6 , wherein a number of the intra-prediction modes is 35 or 67.
8. The method of claim 1 , wherein the transform kernel combination is determined further based on an intra-prediction mode.
9. The method of claim 8 , wherein a number of the transform kernel combinations is four.
10. A method of encoding a video signal, comprising:
generating a residual block of a current block;
generating 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;
generating 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;
performing the transform to the residual block based on the transform kernel combination specified by the index to obtain a transformed block of the current block; and
performing quantization and entropy encoding on the transformed block,
wherein generating the index comprises:
generating an index flag related to generating the index, based on the transform skip flag being 0,
generating the index, based on a value of the index flag being 1, and
deriving 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.
11. A non-transitory decoder-readable storage medium for storing encoded picture information generated by performing the steps of:
generating a residual block of a current block;
generating 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;
generating 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;
performing the transform to the residual block based on the transform kernel combination specified by the index to obtain a transformed block of the current block; and
performing quantization and entropy encoding on the transformed block,
wherein generating the index comprises:
generating an index flag related to generating the index, based on the transform skip flag being 0,
generating the index, based on a value of the index flag being 1, and
deriving 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.