Method and apparatus for video coding

An apparatus, comprising:

• processing circuitry configured to:
• generate a first primary transform coefficient block for a current block based on a primary transform core of the current block;
• determine whether to transpose the first primary transform coefficient block based on a type of one-dimensional cross-component linear model applied to the current block;
• in response to a determination to transpose the first primary transform coefficient block, transpose the first primary transform coefficient block;
• generate a second primary transform coefficient block larger in size than the first primary transform coefficient block by including, in the second primary transform coefficient block, values of the first primary transform coefficient block and a number of 0 values to make a size of the second primary transform coefficient block equal to a size of a secondary transform core;
• generate a secondary transform coefficient block based on (i) the second primary transform coefficient block and (ii) the secondary transform core of the current block, the size of the secondary transform core being greater than a size of the first primary transform coefficient block, and
• encode the current block based on the secondary transform coefficient block.

A method of processing visual media data, the method comprising:

• processing a bitstream of the visual media data according to a format rule, wherein
• the bitstream includes coded information of a current block,
• the format rule specifies that a first primary transform coefficient block is generated for the current block based on a primary transform core of the current block;
• the format rule specifies that whether to transpose the first primary transform coefficient block is determined based on a type of one-dimensional cross-component linear model applied to the current block;
• the format rule specifies that, in response to a determination to transpose the first primary transform coefficient block, transposing the first primary transform coefficient block;
• generating a second primary transform coefficient block larger in size than the first primary transform coefficient block by including, in the second primary transform coefficient block, values of the first primary transform coefficient block and a number of 0 values to make a size of the second primary transform coefficient block equal to a size of a secondary transform core;
• generating a secondary transform coefficient block based on (i) the second primary transform coefficient block and (ii) the secondary transform core of the current block, the size of the secondary transform core being greater than a size of the first primary transform coefficient block, and
• encoding the current block based on the secondary transform coefficient block.