Abstract
The H.264/AVC video coding standard can achieve better compression performance than previous video coding standards, such as MPEG-2, MPEG-4, and H.263, because H.264 encoder employs a rate-distortion (RD) optimization strategy to select the best coding mode. With this strategy, the RD costs for all possible modes are computed and the one with the minimum RD cost is considered the best mode. However, this coding step results in very high computational complexity. Therefore, in this thesis, we propose a fast mode decision algorithm based on mode statistical information and the motion cost of P16×16 mode. The mode statistics information provides the possibility that the mode for a macroblock (MB) is SKIP mode, given that the best modes for the MB’s in some neighborhood of that MB are all SKIP modes. For each MB, the proposed algorithm checks the mode statistical information first in order to terminate the RD optimization calculation as early as possible by using SKIP mode directly to encode this MB. Otherwise, the motion cost of P16×16 mode is obtained to determine which mode category is more likely to contain the true best mode, and the required number of modes considered in the best mode prediction process can be reduced significantly. Experimental results demonstrate that, on average, the proposed approach can save the encoding time by 78.03% and encoding bit rate by 2.06%, while incurring only 0.64 dB drop in PSNR.
Published Version
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