Patent attributes
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 for a frame in a frame header. The default transform mode can be used to encode blocks of the frame. When the default transform mode is a per-block transform mode, the transform size can be determined on a per-block basis and may be included in block headers. When all available transform sizes are not tested for a current block, estimates of a rate distortion value can be performed for the current block using its prediction mode and the remaining transform sizes. Using these estimates and the actual calculated rate distortion values for blocks of the current frame, the default transform mode can be updated for the next frame.
