Research On Mode-Decision Algorithms In The H.264/AVC Video Coding Standard

This paper starts with the introduction of video encoding technology andinternational standards, and the newest H.264/AVC standard which is carefully studiedis included for its application, encoding principle and key technologies what aredifferent from former standards. Then, we discuss two key technologies which areintra-mode encoding and inter-mode encoding by their RDO mode decision tactics,and analyses the advantage and disadvantage of the tactics, then find out a new modedecision method for the high operation and long encoding time which is called TreeDecision Scheme (TDS).First of all, for the intra prediction mode, the H.264/AVC has 16×16 macro blockof 4 mode patterns and 4×4 block of 9 mode patterns with RDO tactics with highcomplication. This paper presents a new method by using quantization parameter (QP)and texture feature of a macro block. The new algorithm chooses block size by usingQP first. Then we choose block size by texture feature of macro block while QP cannot using. Then it predicts the optimum mode in 4×4 block by two steps which calledTwo Level Scheme (TLS), and uses SATD instead of RDO to choose three nearestmodes candidates for the first step of coarse select. Compared with the simple search,this algorithm decreases about 70% of encoding time with little increase of bit-rate.Then, for the inter prediction mode, we first select SKIP mode by 4 decisionnorms for its independence in all inter modes and much occupation in video frames inadvance. Then combined with intra prediction in inter mode, we prior determine intramode by comparing two parameter which are Average Rate (AR) and Average BoundError (ABE). For other modes, we classify them to two mode-sets which aremacro-block and sub-macro-block by the second moment of the histogram which isanalyzed from texture feature. Compared with full search motion estimation in simpleRDO tactics, this method decreases about 50% encoding time with little increase ofbit-rate.The TDS method deceases about 50% encoding time, so this algorithm satisfiesthe real time system in a great degree.