Method and apparatus for processing image signal

An apparatus for decoding an image signal, comprising:

• a memory configured to store the video signal;
• and
• a processor coupled to the memory, wherein the processor is configured to:
• determine an input length and an output length of a non-separable transform based on a height and a width of a current block;
• determine a non-separable transform matrix for the current block, a size of the non-separable transform matrix being determined based on the input length and the output length of the non-separable transform;
• and
• apply the non-separable transform matrix for coefficients of the current block, a number of the coefficients being related to the input length of the non-separable transform,
• wherein the input length and the output length of the non-separable transform are determined separately,
• wherein the input length of the non-separable transform is determined as 16 and the output length of the non-separable transform is greater than the input length of the non-separable transform, based on that both the height and the width of the current block are greater than 8, and
• wherein the input length of the non-separable transform is determined as 8 and the output length of the non-separable transform is greater than the input length of the non-separable transform, based on that both the height and the width of the current block are equal to 8.

A method for encoding an image signal by an apparatus, comprising:

• determining an input length and an output length of a non-separable transform based on a height and a width of a current block;
• determining a non-separable transform matrix for the current block, a size of the non-separable transform matrix being determined based on the input length and the output length of the non-separable transform;
• applying the non-separable transform matrix for coefficients of the current block, a number of the coefficients being related to the input length of the non-separable transform;
• and
• encoding a non-separable transform index information for the non-separable transform matrix for the current block,
• wherein the input length and the output length of the non-separable transform are determined separately,
• wherein the output length of the non-separable transform is determined as 16 and the input length of the non-separable transform is greater than the output length of the non-separable transform, based on that both the height and the width of the current block are greater than 8, and
• wherein the output length of the non-separable transform is determined as 8 and the input length of the non-separable transform is greater than the output length of the non-separable transform, based on that both the height and the width of the current block are equal to 8.

A non-transitory decoder-readable storage medium for storing a bitstream, the bitstream comprising a decoder executable program, the decoder executable program, when executed, causing a decoder to perform the following steps:

• determining an input length and an output length of a non-separable transform based on a height and a width of a current block;
• determining a non-separable transform matrix for the current block, a size of the non-separable transform matrix being determined based on the input length and the output length of the non-separable transform;
• and
• applying the non-separable transform matrix for coefficients of the current block, a number of the coefficients being related to the input length of the non-separable transform,
• wherein the input length and the output length of the non-separable transform are determined separately,
• wherein the input length of the non-separable transform is determined as 16 and the output length of the non-separable transform is greater than the input length of the non-separable transform, based on that both the height and the width of the current block are greater than 8, and
• wherein the input length of the non-separable transform is determined as 8 and the output length of the non-separable transform is greater than the input length of the non-separable transform, based on that both the height and the width of the current block are equal to 8.