Method and device for processing video signal using reduced transform
A method and device for processing a video signal using a reduced transform are provided. A method for decoding a video signal includes splitting a current block into a plurality of subblocks based on a first flag for a split direction of the current block, determining a subblock, to which a transform is applied, among the plurality of subblocks based on a second flag for a position of a transform target block, determining a transform target area in the subblock, and applying an inverse transform including a horizontal transform and a vertical transform to transform coefficients of the transform target area. The transform target area is determined based on a transform type applied to the subblock and a size of the subblock.
1. A method for decoding a video signal, the method comprising:
splitting a current block into a plurality of subblocks based on a first flag for a split direction of the current block;
determining a subblock, to which a transform is applied, among the plurality of subblocks based on a second flag for a position of a transform target block;
determining a transform target area in the subblock; and
applying an inverse transform including a horizontal transform and a vertical transform to transform coefficients of the transform target area,
wherein the transform target area is determined based on a transform type applied to the subblock and a size of the subblock,
wherein a width of the transform target area is determined as a smaller value among a width of the subblock and 16, based on a type index of the horizontal transform being greater than zero, and determined as a smaller value among the width of the subblock and 32, based on the type index of the horizontal transform not being greater than zero, and
wherein a height of the transform target area is determined as a smaller value among a height of the subblock and 16, based on a type index of the vertical transform being greater than zero, and determined as a smaller value among the height of the subblock and 32, based on the type index of the vertical transform not being greater than zero.
2. The method of claim 1 , wherein a remaining area excluding the transform target area from the subblock is derived to be filled with zero.
3. The method of claim 1 , wherein the first flag indicates to split the current block into two transform units in a horizontal direction, or indicates to split the current block into two transform units in a vertical direction.
4. A method for encoding a video signal, the method comprising:
splitting a current block including residual samples into a plurality of subblocks;
determining a subblock to apply a transform from among the plurality of subblocks;
generating a transform block including transform coefficients by applying a horizontal transform and a vertical transform to the subblock; and
encoding information related to the transform,
wherein an area in which a non-zero transform coefficient is present in the transform block is determined based on a transform type applied to the subblock and a size of the subblock,
wherein the information related to the transform includes a first flag for a split direction of the current block and a second flag indicating the subblock to apply the transform from among the plurality of subblocks,
wherein a width of the area, in which a non-zero transform coefficient is present, is determined as a smaller value among a width of the subblock and 16, based on a type index of the horizontal transform being greater than zero, and determined as a smaller value among the width of the subblock and 32, based on the type index of the horizontal transform not being greater than zero, and
wherein a height of the area is determined as a smaller value among a height of the subblock and 16, based on a type index of the vertical transform being greater than zero, and determined as a smaller value among the height of the subblock and 32, based on the type index of the vertical transform not being greater than zero.
5. The method of claim 4 , wherein a remaining area excluding the area, in which the non-zero transform coefficient is present, from the subblock is derived to be filled with zero.
6. The method of claim 4 , wherein the first flag indicates to split the current block into two transform units in a horizontal direction, or indicates to split the current block into two transform units in a vertical direction.
7. A device configured to decode a video signal, the device comprising:
a memory configured to store the video signal; and
a processor coupled to the memory and configured to process the video signal,
wherein the processor is configured to:
split a current block into a plurality of subblocks based on a first flag for a split direction of the current block;
determine a subblock, to which a transform is applied, among the plurality of subblocks based on a second flag for a position of a transform target block;
determine a transform target area in the subblock; and
apply an inverse transform including a horizontal transform and a vertical transform to transform coefficients of the transform target area,
wherein the transform target area is determined based on a transform type applied to the subblock and a size of the subblock,
wherein a width of the transform target area is determined as a smaller value among a width of the subblock and 16, based on a type index of the horizontal transform being greater than zero, and determined as a smaller value among the width of the subblock and 32, based on the type index of the horizontal transform not being greater than zero, and
wherein a height of the transform target area is determined as a smaller value among a height of the subblock and 16, based on a type index of the vertical transform being greater than zero, and determined as a smaller value among the height of the subblock and 32, based on the type index of the vertical transform not being greater than zero.
8. A device configured to encode a video signal, the device comprising:
a memory configured to store the video signal; and
a processor coupled to the memory and configured to process the video signal,
wherein the processor is configured to:
split a current block including residual samples into a plurality of subblocks;
determine a subblock to apply a transform from among the plurality of subblocks;
generate a transform block including transform coefficients by applying a horizontal transform and a vertical transform to the subblock; and
encode information related to the transform,
wherein an area in which a non-zero transform coefficient is present in the transform block is determined based on a transform type applied to the subblock and a size of the subblock,
wherein the information related to the transform includes a first flag for a split direction of the current block and a second flag indicating the subblock to apply the transform from among the plurality of subblocks,
wherein a width of the area, in which a non-zero transform coefficient is present, is determined as a smaller value among a width of the subblock and 16, based on a type index of the horizontal transform being greater than zero, and determined as a smaller value among the width of the subblock and 32, based on the type index of the horizontal transform not being greater than zero, and
wherein a height of the area, in which a non-zero transform coefficient is present, is determined as a smaller value among a height of the subblock and 16, based on a type index of the vertical transform being greater than zero, and determined as a smaller value among the height of the subblock and 32, based on the type index of the vertical transform not being greater than zero.
9. A non-transitory computer-readable medium storing a bitstream generated by a method, the method comprising:
splitting a current block including residual samples into a plurality of subblocks;
determining a subblock to apply a transform from among the plurality of subblocks;
generating a transform block including transform coefficients by applying a horizontal transform and a vertical transform to the subblock; and
encoding information related to the transform,
wherein an area in which a non-zero transform coefficient is present in the transform block is determined based on a transform type applied to the subblock and a size of the subblock,
wherein the information related to the transform includes a first flag for a split direction of the current block and a second flag indicating the subblock to apply the transform from among the plurality of subblocks,
wherein a width of the area, in which a non-zero transform coefficient is present, is determined as a smaller value among a width of the subblock and 16, based on a type index of the horizontal transform being greater than zero, and determined as a smaller value among the width of the subblock and 32, based on the type index of the horizontal transform not being greater than zero, and
wherein a height of the area, in which a non-zero transform coefficient is present, is determined as a smaller value among a height of the subblock and 16, based on a type index of the vertical transform being greater than zero, and determined as a smaller value among the height of the subblock and 32, based on the type index of the vertical transform not being greater than zero.