Patent ID: 8824812

Claim:
A method of image data compression for compressing frame or image buffer in an image or video coding system, the method comprising: receiving image data to be stored in the frame or image buffer, wherein the image data is partitioned into a plurality of access units; applying first data compression to each access unit to generate a first bitstream for the access unit, wherein size of the first bitstream is smaller than or equal to a target bit budget for the access unit; in response to result of the first data compression, applying second data compression to residual data of the access unit to generate a second bitstream for the access unit, wherein the residual data corresponds to first differences between original image data of the access unit and first reconstructed image data corresponding to the first data compression of the access unit; providing the first bitstream for storing in the frame or image buffer; and providing the second bitstream for storing in the frame or image buffer if the second bitstream exists.