Selection of transform size in video coding

摘要

Blocks of a frame of a video stream can be encoded using various prediction modes followed by transforming the predicted blocks. Increasing coding efficiency may be achieved by indicating a default transform mode in a frame header. The default transform mode is a maximum transform size for all blocks of the frame or a per-block transform mode that determined the transform size on a per-block basis. For encoded blocks of the frame, identify a prediction mode is identified by inspecting a block header of a current encoded block, the block header of the current encoded block is inspected if the default transform mode is the per-block transform mode so as to identify a transform size for the current encoded block, and otherwise the transform size for the current encoded block is the maximum transform size, and the current encoded block is decoded using the prediction mode and the transform mode.

主权项

1. A method for decoding an encoded video bitstream having a plurality of frames in a sequence, the method comprising:
identifying a default transform mode for a current frame of a plurality of frames by inspecting a frame header of the current frame; and for a plurality of encoded blocks of the current frame:
identifying a prediction mode by inspecting a block header of a current encoded block of the plurality of encoded blocks;identifying a transform size for the current encoded block by inspecting the block header of the current encoded block if the default transform mode is a per-block transform mode;identifying the transform size for the current encoded block as a frame-level transform size associated with the default transform mode if the default transform mode is not the per-block transform mode;inverse transforming the current encoded block using the transform size to obtain a current inverse transformed block; andusing a processor, decoding the current inverse transformed block using the identified prediction mode.