Method and apparatus of improved intra prediction mode coding

摘要

A method and apparatus for improved intra chroma prediction mode coding are disclosed. Intra prediction exploits the spatial correlation within a picture or within a picture region. In practice, a picture is divided into blocks and the intra mode prediction is performed on a block basis. In newer coding systems, multiple intra coding modes such as Vertical mode, Horizontal mode, DC mode and Diagonal mode, have been used to improve the coding efficiency of intra coding. Furthermore, a Luma_mode has also been used in intra prediction of chroma component to further improve the performance in the High Efficiency Video Coding (HEVC) standard being developed. However, the mode selection information for intra prediction has to be conveyed to the decoder for proper operation. Spatial features in a picture often exist in both luma and chroma components. The intra luma prediction mode and intra chroma prediction mode will have high probability to be the same. Accordingly, an embodiment according to the present invention adaptively assigns variable length codes to a set of mode symbols associated with intra chroma prediction by assigning a shortest code to the Luma_mode. Luma_mode not only can be the best luma mode of the corresponding luma block but also can be selected from several corresponding luma modes. The maximum length of chroma prediction codes is decreased by one bit when Luma_mode is equal to one of frequent modes. The coding efficiency of arithmetic coding of chroma prediction codes is further improved by selecting the context upon neighboring blocks.

主权项

1. A method of coding intra chroma prediction mode of a chroma block, the method comprising:
receiving a set of chroma mode symbols associated with the intra chroma prediction mode of the chroma block, wherein the set of chroma mode symbols includes one entry associated with Luma_mode to allow the chroma block to use an intra luma prediction mode of a corresponding luma block or an selected intra luma prediction mode of several corresponding luma blocks as the intra chroma prediction mode; determining variable length codes for the set of chroma mode symbols, wherein a shortest length code is assigned to the Luma_mode; receiving a current intra chroma prediction mode for a current chroma block; determining a chroma prediction code for the current intra chroma prediction mode of the current chroma block according to the variable length codes; and applying intra predictive coding to the current chroma block using the intra luma prediction mode of the corresponding luma block or the selected intra luma prediction mode of several corresponding luma blocks when the Luma_mode is selected for the current intra chroma prediction mode.