Method and apparatus of adaptive multiple transforms for video coding
A method and apparatus for video encoding or decoding performed by a video encoder or a video decoder incorporating advanced multiple transform (AMT) are disclosed. According to this method, a transform set consisting of two type candidates designated as a first type and a second type is determined, where the first type and the second type are different. If AMT is used by the current block, a vertical transform is selected from the transform set and a horizontal transform is selected from the transform set. A transform index, for indicating both vertical transform selection and horizontal transform selection, can be signaled at the encoder side or the transform index is parsed at the decoder side. Another method and apparatus incorporating AMT are also disclosed where the transform set is determined according to the resolution of current MVD.
1. A method for encoding or decoding video data, the method comprising:
receiving input data associated with a current block, wherein the input data corresponds to the current block to be processed by a forward transform process at an encoder side and the input data corresponds to a current coefficient block to be processed by an inverse transform process at a decoder side;
determining a single transform set consisting of two transform type candidates designated as a first transform candidate type and a second transform candidate type or consisting of three transform candidates types corresponding to the first transform candidate type, the second transform candidate type and a flipped second transform candidate type, wherein the first transform candidate type and the second transform candidate type are different; and
selecting a vertical transform and a horizontal transform from the single transform set if AMT (adaptive multiple transform) is used by the current block; and
generating a current coefficient block according to the current block, the vertical transform and the horizontal transform at the encoder side or recovering the current block according to the current coefficient block, a vertical inverse transform associated with the vertical transform and a horizontal inverse transform associated with the horizontal transform at the decoder side,
wherein when AMT is used by the current block, the first transform candidate is available for the current block if a size of the current block ranges between a minimum size and a maximum size, and the second transform candidate is available for the current block if the size of the current block ranges between the minimum size and a half of the maximum size.
2. The method of claim 1 , wherein the first transform candidate corresponds to DCT-II (Discrete Cosine Transform Type II) and the second transform candidate is selected from a group comprising DST-IV (Discrete Sine Transform Type IV), DST-VII (Discrete Sine Transform Type VII) and flipped DCT-IV (FDCT-IV, Flipped Discrete Cosine Transform Type IV).
3. The method of claim 2 , wherein, if AMT is not used by the current block, the first transform candidate is selected for both the vertical transform and the horizontal transform.
4. The method of claim 2 , wherein, if AMT is used by the current block, the vertical transform and the horizontal transform select different transform candidates or both the vertical transform and the horizontal transform select the second transform candidate.
5. The method of claim 1 , wherein the size related to of the current block corresponds to transform block size.
6. The method of claim 1 , wherein the size of the current block corresponds to transform width or transform height.
7. The method of claim 6 , wherein the minimum size corresponds to a minimum transform width and a minimum transform height, and the maximum size corresponds to a maximum transform width and a maximum transform height.
8. An apparatus for encoding or decoding video data, the apparatus comprising one or more electronic circuits or processors arranged to:
receive input data associated with a current block, wherein the input data corresponds to the current block to be processed by a forward transform process at an encoder side and the input data corresponds to a current coefficient block to be processed by an inverse transform process at a decoder side;
determine a single transform set consisting of two transform type candidates designated as a first transform candidate type and a second transform candidate type or consisting of three transform candidates types corresponding to the first transform candidate type, the second transform candidate type and a flipped second transform candidate type, wherein the first transform candidate type and the second transform candidate type are different; and
select a vertical transform and a horizontal transform from the single transform set if AMT (adaptive multiple transform) is used by the current block; and
generate a current coefficient block according to the current block, the vertical transform and the horizontal transform at the encoder side or recovering the current block according to the current coefficient block, a vertical inverse transform associated with the vertical transform and a horizontal inverse transform associated with the horizontal transform at the decoder side,
wherein when AMT is used by the current block, the first transform candidate is available for the current block if a size of the current block ranges between a minimum size and a maximum size, and the second transform candidate is available for the current block if the size of the current block ranges between the minimum size and a half of the maximum size.