Primary transforms for cross-component level reconstruction

A device for video processing, the device comprising a memory for storing computer instructions and a processor in communication with the memory, wherein, when the processor executes the computer instructions, the processor is configured to cause the device to:

• encode a video block comprising a first transform block of a first color component and a second transform block of a second color component, wherein the first transform block and the second transform blocks are co-located blocks;
• encode a first syntax element to signal whether a cross component level reconstruction (CCLR) is applied to the first transform block, wherein, when the CCLR is applied to the first transform block, a refinement process is required to be applied to the first transform block to obtain a refined first transform block on which an inverse transform is to be performed;
• and
• transmit a bitstream comprising the video block and the first syntax element, wherein:
• the bitstream comprises an explicit indication or an implicit indication indicating that all transform coefficients in the first transform block are zero.

A non-transitory storage medium for storing computer readable instructions, the computer readable instructions, when executed by a processor of device for processing video data, causing the processor to:

• encode a video block comprising a first transform block of a first color component and a second transform block of a second color component, wherein the first transform block and the second transform blocks are co-located blocks;
• encode a first syntax element to signal whether a cross component level reconstruction (CCLR) is applied to the first transform block, wherein, when the CCLR is applied to the first transform block, a refinement process is required to be applied to the first transform block to obtain a refined first transform block on which an inverse transform is to be performed;
• and
• transmit a bitstream comprising the video block and the first syntax element, wherein:
• the bitstream comprises an explicit indication or an implicit indication indicating that all transform coefficients in the first transform block are zero.