Efficient Partial Decoding Scheme for Intra Frame in H.264/AVC Stream

Partial decoding is an effective way to improve the processing efficiency in many video applications such as video retrieval and mobile video display. But after many advanced prediction technology were introduced into video coding, partial decoding encountered many difficulties due to the strong data dependency of the high compressed stream. In this paper, one partial decoding scheme is presented, in which user can specify the region of interest(ROI) to be decoded. In particular, we focus on dealing with the decoding the specified region of the intra slice data in the H.264/AVC stream. To decode the ROI, we build one decoding dependency graph (DDG) to collect all necessary information during parsing the corresponding data. And then we reconstruct one macroblock(MB), or skip it, which depends on the MB's dependency state in the DDG. Furthermore, one simplified decoding dependency graph(SDDG) is proposed, in which less important dependency is removed from DDG to speed up decoding. One decoder with support DDG and SDDG is implemented and some typical video streams are used to evaluate the proposed decoding system. Experiments show that the proposed partial decoding scheme can save the decoding time efficiently with negligible decoded picture quality loss.