Optimization And Realization Of H.264 Decoding Technology On Embedded System

As the new generation of video decoding standard,H.264/AVC using a series of advanced algorithm, vastly improved codec effieiency. But it also leads to a significant increase in the amount of computing, constraint widespread use of H.264 standard in video area especially on these embedded equipment in which hardware configuration are general low. The H.264 decoding technology is hardly to apply to. So how to optimize H.264 decoder to achieve fluent play back of H.264 stand video is an oncoming train.This thesis tries to analyze the H.264 video codec standard, and the decoding process of JM, which is one of the implementation model of H.264 stand. It turns out that the time consumption of deblocking filter module and motion estimation module are much larger, so we made improvement to reduce the time consumption for these two modules. For deblocking filter module, this module is made up of boundary strength(BS) and filter implementation, among which boundary strength consumed 90% of the time of total deblocking filter. In general video sequences, two adjacent frames has temporal correlation, that means video content during these two frames are much the same, so we proposed to use boundary strength of macroblock in one frame to predict the boundary strength of macroblock in adjacent frame, which could avoid complex calculation. For motion estimation module, the original JM decoder use 4x4 sub-block as basic unit for motion estimation.There are mount of macroblock use SKIP and 16x16 mode as codeing mode, only a little block use 4x4 mode. Further more, H.264 stand says that all 4x4 sub-block in current block has the same motion estimation process, so based on this theory we realized use current block's mode as basic unit of interpolation to make the motion estimation process simple.In order to achieve an embedded H.264 decoder, this thesis use MINI2440 development board as hardware platform, transplanted UBoot and Linux 2.6.13 Operating system,made Yaffs file system, and finally build the embedded platform successfully. After optimization for the hardware features, we realized H.264 decoder which based on ARM+Linux platform. Experimental results show that the decoder realized by this thesis could significantly improve the decoding speed when deal with less dramatic changes in the content of video sequences.