Fast Mode Decision Strategy for H. 264 Frame Skipping Transcoding
Mode selection in H. 264 /AVC coding is determined by value of the rate distortion optimization( RDO),RDO standard algorithm searchs all coding modes supported by H. 264 and calculates their rate distortion value,then select the mode with smallest value as the optimal coding mode. To solve compatibility problems of video stream in different network environments,frame skipping transcoding uses also the RDO technology to improve the efficiency of the transcoding. With the analysis of the information contained in the inputted video stream of frame skipping transcoding,the introduction of two motion characteristics critical threshold to determine the motion feature of the current macro block makes it possible to properly discard unnecessary mode searching. Combination of these two motion threshold,new model selection strategy uses a core function to abtain more approximate data of current macroblock real movement which achieves more accurate portraying and determine the motion characteristics of the current macro block. Simulation results show that the fast mode selection strategy reasonablely solutes the mapping and using of mode information under the conditions of frame skipping transcoding,higher the coding efficiency and robust,and obtains more reliable transcoding video quality, which make it can be widely applied to real-time interactive of video data in complex and changing network environment.