A predictive block-size mode selection for inter frame in H.264

One of the new features adopted in the latest H.264/AVC video coding standard is the mode decision (MD), which greatly improves the rate-distortion performance but it also takes up a significant encoding time to determine the best mode. This paper presents a predictive block-size selection algorithm to extraordinarily improve the encoding efficiency in H.264. The proposed algorithm mainly takes advantage of two efficient predictive methods: one is predictive skipping checking the sub-macroblock-level modes according to the sum of absolute difference (SAD) of each macroblock and the other is filtering some sub-macroblock-level modes with an adaptive threshold obtained from the mode information in the previous determined macroblock. Experimental results and comparative analysis are given to verify that our proposed algorithm can achieve a speed-up factor with 30% compared with the current Fast Full Search algorithm, with negligible average PSNR loss of 0.071dB and bit rate increase of 2.78%.