Method and apparatus of the quantization matrix computation and representation for video coding
A method and apparatus for video coding using a coding mode belonging to a mode group comprising an Intra Block Copy (IBC) mode and an Intra mode are disclosed. According to the present invention, for both IBC and Intra mode, a same default scaling matrix is used to derive the scaling matrix for a current block. In another embodiment, for the current block with block size of M×N or N×M, and M greater than N, a target scaling matrix is derived from an M×M scaling matrix by down-sampling the M×M scaling matrix to an M×N or N×M scaling matrix.
1. A method of video coding using a coding mode belonging to a mode group comprising an Intra Block Copy (IBC) mode and an Inter mode, the method comprising:
receiving input data related to a current block in a current picture, wherein the input data correspond to a transform block of the current block at a video encoder side and the input data correspond to a decoded-quantized transform block of the current block at a video decoder side;
determining a current coding mode for the current block;
when the current coding mode corresponds to the IBC mode:
deriving a scaling matrix from a shared base scaling matrix, the shared base scaling matrix comprising a default square matrix, the scaling matrix comprising a rectangular matrix based on up-sampling, down-sampling, or up-sampling and down-sampling according to the shared base scaling matrix; and
applying an inverse quantization process to the input data according to the scaling matrix to generate a decoded transform block at the video decoder side, wherein the inverse quantization process uses the scaling matrix to generate the decoded transform block;
wherein the shared base scaling matrix is applied to another quantization process or another inverse quantization process in another coding mode corresponding to the Inter mode in the mode group.
2. The method of claim 1 , further comprising applying a quantization process to the input data according to the scaling matrix to generate a coded-quantized transform block at the video encoder side.
3. An apparatus of video coding using a coding mode belonging to a mode group comprising an Intra Block Copy (IBC) mode and an Inter mode and the apparatus comprising one or more electronic circuits or processors arranged to:
receive input data related to a current block in a current picture, wherein the input data correspond to a transform block of the current block at a video encoder side and the input data correspond to a decoded-quantized transform block of the current block at a video decoder side;
determine a current coding mode for the current block;
when the current coding mode corresponds to the IBC mode:
derive a scaling matrix from a shared base scaling matrix, the shared base scaling matrix comprising a default square matrix, the scaling matrix comprising a rectangular matrix based on up-sampling, down-sampling, or up-sampling and down-sampling according to the shared base scaling matrix; and
apply a quantization process to the input data according to the scaling matrix to generate a coded-quantized transform block at the video encoder side or apply an inverse quantization process to the input data according to the scaling matrix to generate a decoded transform block at the video decoder side, wherein the quantization process uses the scaling matrix to generate the coded-quantized transform block, and the inverse quantization process uses the scaling matrix to generate the decoded transform block;
wherein the shared base scaling matrix is applied for to another quantization process or another inverse quantization process in another coding mode corresponding to the Inter mode in the mode group.
4. The apparatus of video coding of claim 3 , wherein said one or more electronic circuits or processors are arranged to apply a quantization process to the input data according to the scaling matrix to generate a coded-quantized transform block at the video encoder side.