Methods and apparatuses for processing video signal
Embodiments of the present invention provide video signal processing methods. A video signal encoding method according to an embodiment of the present invention comprises checking a transform block including residual samples except a prediction sample from a picture of the video signal, generating transform coefficients through a transform for the residual samples of the transform block based on a size of the transform block, and performing quantization and entropy coding the transform coefficients, wherein generating the transform coefficients includes, applying a forward primary transform to each of a horizontal direction and vertical direction of the transform block including the residual samples, and not applying a forward non-separable secondary transform to the transform block to which the primary transform has been applied when the size of the transform block is smaller than or equal to 4×4, and applying the forward non-separable secondary transform to the transform block when the size of the transform block is greater than 4×4.
1. A method of decoding a video signal by an apparatus, comprising:
deriving an intra prediction mode of a current block;
obtaining transform coefficients by performing entropy decoding and inverse quantization for the current block;
obtaining residual data through an inverse transform for the transform coefficients of the current block;
generating prediction data based on the intra prediction mode; and
reconstructing an image based on the residual data and the prediction data, wherein performing the inverse transform includes:
obtaining a secondary transform index based on a non-zero transform coefficient not positioned in a specific region,
wherein the specific region represents a region other than a position where the non-zero transform coefficient exists when a reduced secondary transform is applied and transform coefficients are arranged according to a scan order; and
performing an inverse secondary transform on the transform coefficients based on an inverse secondary transform matrix derived based on the secondary transform index; and
performing an inverse primary transform on the transform coefficients to which the inverse secondary transform is applied,
wherein the secondary transform index represents that one of 2 transform kernels in a transform set is used, and the transform set is determined based on the intra prediction mode, and
wherein the inverse primary transform includes a horizontal transform and a vertical transform for the transform block, and a combination of the horizontal transform and the vertical transform is determined as one of a combination of DCT-2 and DCT-2, a combination of DCT-8 and DCT8, a combination of DST-7 and DCT-8, a combination of DCT-8 and DST-7 and a combination of DST-7 and DST-7, based on a syntax element related to the horizontal transform and the vertical transform.
2. The method of claim 1 ,
wherein the transform set for an intra prediction mode 52 is determined as the same transform set for an intra prediction mode 16 .
3. The method of claim 1 ,
wherein the inverse secondary transform corresponding to the reduced secondary transform represents a transform outputting N first data (N×1 vectors) based on inputted L (L<N) second data (L×1 vectors).
4. Method of encoding a video signal by an apparatus, comprising:
determining an intra prediction mode of a current block;
generating residual data except prediction data from an image of the video signal;
generating transform coefficients of the current block through a transform for the residual data; and
performing quantization and entropy coding for the transform coefficients, wherein generating the transform coefficients includes:
performing a primary transform on the residual data to obtain transform coefficients;
deriving a secondary transform matrix to be applied to the transform coefficients;
performing a secondary transform on the transform coefficients based on the secondary transform matrix; and
generating a secondary transform index based on a non-zero transform coefficient not positioned in a specific region,
wherein the specific region represents a region other than a position where the non-zero transform coefficient exists when a reduced secondary transform is applied and transform coefficients are arranged according to a scan order, and
wherein the secondary transform index represents that one of 2 transform kernels in a transform set is used, and the transform set is determined based on the intra prediction mode, and
wherein the primary transform includes a horizontal transform and a vertical transform for the transform block, and a combination of the horizontal transform and the vertical transform is determined as one of a combination of DCT-2 and DCT-2, a combination of DCT-8 and DCT8, a combination of DST-7 and DCT-8, a combination of DCT-8 and DST-7 and a combination of DST-7 and DST-7.
5. The method of claim 4 ,
wherein the transform set for an intra prediction mode 52 is determined as the same transform set for an intra prediction mode 16 .
6. The method of claim 4 ,
wherein the secondary transform matrix represents the reduced secondary transform outputting L second data (L×1 vectors) based on inputted N (N>L) first data (N×1 vectors).
7. A non-transitory computer-readable medium storing video information generated by an encoding method, the encoding method comprising:
determining an intra prediction mode of a current block;
generating residual data except prediction data from an image of the video signal;
generating transform coefficients of the current block through a transform for the residual data; and
performing quantization and entropy coding for the transform coefficients,
wherein generating the transform coefficients includes:
performing a primary transform on the residual data to obtain transform coefficients;
deriving a secondary transform matrix to be applied to the transform coefficients;
performing a secondary transform on the transform coefficients based on the secondary transform matrix; and
generating a secondary transform index based on a non-zero transform coefficient not positioned in a specific region,
wherein the specific region represents a region other than a position where the non-zero transform coefficient exists when a reduced secondary transform is applied and transform coefficients are arranged according to a scan order, and
wherein the secondary transform index represents that one of 2 transform kernels in a transform set is used, and the transform set is determined based on the intra prediction mode, and
wherein the primary transform includes a horizontal transform and a vertical transform for the transform block, and a combination of the horizontal transform and the vertical transform is determined as one of a combination of DCT-2 and DCT-2, a combination of DCT-8 and DCT8, a combination of DST-7 and DCT-8, a combination of DCT-8 and DST-7 and a combination of DST-7 and DST-7.