Video signal processing method and apparatus using scaling process
The present disclosure relates to a processing method of a video signal, the processing method comprising the steps of: scaling a transform coefficient for a current block on the basis of an intermediate scaling factor array; when the flag indicates that a low frequency non-separable transform is applied to the current block, obtaining a residual for the current block by applying an inverse transform of a non-separable transform and an inverse transform of a primary transform on the scaled transform coefficient, wherein the primary transform is a transform applied to a residual signal of a spatial domain before the low frequency non-separable transform; and reconstructing the current block on the basis of the residual and a predictor of the current block.
1. A video signal encoding apparatus comprising a processor,
wherein the processor is configured to:
obtain a bitstream to be decoded by a decoder using a decoding method,
the decoding method comprising:
scaling a transform coefficient for a current block based on an intermediate scaling factor array;
when a flag indicating whether a low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block, obtaining a residual for the current block by applying an inverse transform of a primary transform to a coefficient, the coefficient is obtained by applying an inverse transform of the low frequency non-separable transform to the scaled transform coefficient,
wherein the flag indicating whether the low frequency non-separable transform is applied is determined based on a low frequency non-separable transform index,
wherein the low frequency non-separable transform index indicates whether the low frequency non-separable transform is applied and a kernel to be used for the low frequency non-separable transform,
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block, obtaining the residual for the current block by applying the inverse transform of the primary transform to the scaled transform coefficient; and
reconstructing the current block based on the residual,
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block and a scaling factor array non-use flag indicates non-use of a scaling matrix for the current block, all factors included in the intermediate scaling factor array are set to one predetermined value.
2. The video signal encoding apparatus of claim 1 ,
wherein when the low frequency non-separable transform is applied to the current block, a prediction mode of the current block is an intra prediction mode.
3. The video signal encoding apparatus of claim 1 ,
wherein when a flag indicating whether transform is applied to the current block indicates that transform is not applied, the all factors included in the intermediate scaling factor array are set to the one predetermined value.
4. The video signal encoding apparatus of claim 1 ,
wherein the intermediate scaling factor array is derived based on values obtained from the bitstream when failing to set the all factors included in the intermediate scaling factor array to the one predetermined value.
5. The video signal encoding apparatus of claim 1 ,
wherein the scaling factor array non-use flag is obtained from at least one of a sequence parameter set (SPS), a picture parameter set (PPS), a picture header, and a slice header of the bitstream.
6. The video signal encoding apparatus of claim 1 ,
wherein the flag indicating whether the low frequency non-separable transform is applied is determined further based on a type of a current coding tree.
7. The video signal encoding apparatus of claim 6 ,
when the type of the current coding tree is a SINGLE_TREE or DUAL_TREE LUMA:
wherein when the low frequency non-separable transform index is 0, the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block,
wherein when the low frequency non-separable transform index is not 0, the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block,
wherein a color component of the current block is a luma component,
wherein the SINGLE_TREE indicates that a single tree is used to partition the current coding tree including the current block,
wherein the DUAL_TREE_LUMA indicates that a dual tree is used to partition the current coding tree including the current block and the luma component is currently processed.
8. The video signal processing encoding apparatus of claim 6 ,
wherein when the low frequency non-separable transform index is 0 or the type of the current coding tree is not a DUAL_TREE_CHROMA, the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block,
wherein when the low frequency non-separable transform index is not 0 and the type of the current coding tree is the DUAL_TREE_CHROMA, the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block,
wherein a color component of the current block is a chroma component,
wherein the DUAL_TREE_CHROMA indicates that a dual tree is used to partition the current coding tree and the chroma component is currently processed.
9. The video signal encoding apparatus of claim 1 , wherein the one predetermined value is 2{circumflex over ( )}N, and N is a natural number.
10. The video signal encoding apparatus of claim 1 , wherein the one predetermined value is 16.
11. A video signal decoding apparatus comprising a processor,
wherein the processor is configured to:
scale a transform coefficient for a current block based on an intermediate scaling factor array,
when a flag indicating whether a low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block, obtain a residual for the current block by applying an inverse transform of a primary transform to a coefficient, the coefficient is obtained by applying an inverse transform of the low frequency non-separable transform to the scaled transform coefficient,
wherein the flag indicating whether the low frequency non-separable transform is applied is determined based on a low frequency non-separable transform index,
wherein the low frequency non-separable transform index indicates whether the low frequency non-separable transform is applied and a kernel to be used for the low frequency non-separable transform,
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block, obtain the residual for the current block by applying the inverse transform of the primary transform to the scaled transform coefficient,
reconstruct the current block based on the residual,
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block and a scaling factor array non-use flag indicates non-use of a scaling matrix for the current block, all factors included in the intermediate scaling factor array are set to one predetermined value.
12. The video signal decoding apparatus of claim 11 ,
wherein when the low frequency non-separable transform is applied to the current block, a prediction mode of the current block is an intra prediction mode.
13. The video signal decoding apparatus of claim 11 ,
wherein when a flag indicating whether transform is applied to the current block indicates that transform is not applied, the all factors included in the intermediate scaling factor array are set to the one predetermined value.
14. The video signal decoding apparatus of claim 11 ,
wherein the intermediate scaling factor array is derived based on values obtained from the bitstream when failing to set the all factors included in the intermediate scaling factor array to the one predetermined value.
15. The video signal decoding apparatus of claim 11 ,
wherein the scaling factor array non-use flag from at least one of a sequence parameter set (SPS), a picture parameter set (PPS), a picture header, and a slice header of the bitstream.
16. The video signal decoding apparatus of claim 11 ,
when the type of the current coding tree is a SINGLE_TREE or DUAL_TREE_LUMA:
wherein when the low frequency non-separable transform index is 0, the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block,
wherein when the low frequency non-separable transform index is not 0, the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block,
wherein a color component of the current block is a luma component,
wherein the SINGLE_TREE indicates that a single tree is used to partition the current coding tree including the current block,
wherein the DUAL_TREE_LUMA indicates that a dual tree is used to partition the current coding tree including the current block and the luma component is currently processed.
17. A non-transitory computer-readable medium storing a bitstream, the bitstream being decoded by a decoding method,
the decoding method, comprising:
scaling a transform coefficient for a current block based on an intermediate scaling factor array;
when a flag indicating whether a low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block, obtaining a residual for the current block by applying an inverse transform of a primary transform to a coefficient, the coefficient is obtained by applying an inverse transform of the low frequency non-separable transform to the scaled transform coefficient,
wherein the flag indicating whether the low frequency non-separable transform is applied is determined based on a low frequency non-separable transform index,
wherein the low frequency non-separable transform index indicates whether the low frequency non-separable transform is applied and a kernel to be used for the low frequency non-separable transform,
wherein the inverse transform of the primary transform is an inverse transform applied after the inverse transform of the low frequency non-separable transform;
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block, obtaining the residual for the current block by applying the inverse transform of the primary transform to the scaled transform coefficient; and
reconstructing the current block based on the residual,
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block and a scaling factor array non-use flag indicates non-use of a scaling matrix for the current block, all factors included in the intermediate scaling factor array are set to one predetermined value.
18. A method for processing a video signal, the method comprising:
scaling a transform coefficient for a current block based on an intermediate scaling factor array;
when a flag indicating whether a low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block, obtaining a residual for the current block by applying an inverse transform of a primary transform to a coefficient, the coefficient is obtained by applying an inverse transform of the low frequency non-separable transform to the scaled transform coefficient,
wherein the flag indicating whether the low frequency non-separable transform is applied is determined based on a low frequency non-separable transform index,
wherein the low frequency non-separable transform index indicates whether the low frequency non-separable transform is applied and a kernel to be used for the low frequency non-separable transform,
wherein the inverse transform of the primary transform is an inverse transform applied after the inverse transform of the low frequency non-separable transform;
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is not applied to the current block, obtaining the residual for the current block by applying the inverse transform of the primary transform to the scaled transform coefficient; and
reconstructing the current block based on the residual,
when the flag indicating whether the low frequency non-separable transform is applied indicates that the low frequency non-separable transform is applied to the current block and a scaling factor array non-use flag indicates non-use of a scaling matrix for the current block, all factors included in the intermediate scaling factor array are set to one predetermined value.