Method and device for video coding using various transform techniques
The present invention relates to a method and a device for decoding an image, which improve encoding and decoding efficiency by performing various forms of transform and inverse transform during transform and inverse transform processes of a video coding technique.
1. A method of decoding a video, the method comprising:
generating a prediction signal of a current block;
obtaining a transform type index for the current block from a bitstream, the transform type index indicating one of a plurality candidate transform types, each of the plurality of candidate transform types including a horizontal transform type and a vertical transform type, each of the horizontal transform type and the vertical transform type being one of pre-defined transform types, the pre-defined transform types including a DCT-based transform type, a DST-based transform type, and an identity transform type;
determining, based on the transform type index, a transform type of the current block from the plurality of candidate transform types;
generating a residual signal of the current block by performing, based on the transform type, inverse transform on the current block in horizontal and vertical directions; and
reconstructing the current block based on the prediction signal and the residual signal.
2. The method of claim 1 , wherein a number of the candidate transform types is adaptively determined based on a size of the current block.
3. The method of claim 2 , wherein the number of the candidate transform types available for the current block being greater than 16×16
is less than the number of the candidate transform types available for the current block being less than or equal to 16×16.
4. A method of encoding a video, the method comprising:
generating a prediction signal of a current block;
deriving a residual signal of the current block based on the prediction signal; and
performing transform on the residual signal of the current block based on a transform type,
wherein the transform type is determined as one of a plurality of candidate transform types,
wherein a transform type index indicating the one of the plurality of candidate transform types is encoded into a bitstream,
wherein each of the plurality of candidate transform types includes a horizontal transform type and a vertical transform type,
wherein each of the horizontal transform type and the vertical transform type is one of pre-defined transform types, and
wherein the pre-defined transform types include a DCT-based transform type, a DST-based transform type, and an identity transform type.
5. A method of transmitting data for a video signal, the method comprising:
generating a prediction signal of a current block;
deriving a residual signal of the current block based on the prediction signal;
generating a bitstream by encoding the residual signal of the current block; and
transmitting the data including the bitstream,
wherein encoding the residual signal of the current block comprises performing transform on the residual signal of the current block based on a transform type,
wherein the transform type is determined as one of a plurality of candidate transform types,
wherein a transform type index indicating the one of the plurality of candidate transform types is encoded into the bitstream,
wherein each of the plurality of candidate transform types includes a horizontal transform type and a vertical transform type,
wherein each of the horizontal transform type and the vertical transform type is one of pre-defined transform types, and
wherein the pre-defined transform types include a DCT-based transform type, a DST-based transform type, and an identity transform type.