Optimization And Implementation Of H.264 Decoder On DSP And Smartphone Platforms

H.264 is a novel video coding standard developed jointly by ITU (International Telecommunication Union) and ISO (International Organization for Standardization). It adopts many advanced coding technologies and hence achieves outstanding compression performance and network friendliness. It can meet the requirements of various kinds of video applications. Consequently, H.264 will have bright prospects in a variety of fields, such as video communication, media streaming and digital broadcasting. However, the enhancement in coding efficiency of H.264 has been achieved at the cost of a considerable increase in computational complexity. Recently, the optimization and implementation of H.264 encoder and decoder on different platforms have become a hot topic in many research fields and industries.Currently, DSP (Digital Signal Processor) technology is developing rapidly. High performance DSPs provide an ideal platform for computationally intensive multimedia applications. TI DM642 is a high performance fixed-point DSP that is suitable for digital media applications. BREW and Symbian OS are two kinds of smartphone platforms which are widely used nowadays. Mobile media streaming services on BREW and Symbian OS are booming.In this paper, the research on the optimization and implementation of H.264 baseline profile decoder is carried out on DSP and smartphone platforms. Because a decoder is supposed to be compatible with a wide range of bitstreams, the paper chooses JM73 open-source decoder as the object to be optimized. Based on the analysis of the computational complexity of JM73 decoder, we perform PC platform optimization on its program structure, data structure and algorithms. These efforts contribute to a remarkable acceleration in decoding speed, which is indispensable to the optimization and implementation on DSP and smartphone platforms.On DSP platform, the H.264 decoder is optimized in several aspects, including the use of program memory, data memory and assembly language. The speed of the decoder is again increased. Experimental results show that the optimized decoder is able to process H.264 bitstream in both CIF (352×288) and D1 (720×576) formats on real-time basis. Additionally, taking advantage of different mechanisms in the real-time operating system DSP/BIOS, the paper designs a real-time network video transmission system based on the H.264 decoder. The system achieves many functions, such as receiving H.264 data from network, real-time decoding of the compressed bitstream and displaying the reconstructed images on a monitor. In the decoder centered client terminal, good video quality can be provided and the decoder is designed to cooperate with H.264 video server.In addition to all the research work mentioned above, this paper implements H.264 decoder on BREW platform and Symbian OS respectively. In wireless networks, the error rate is high and thus the video playing may always be interrupted. To tackle this problem, an error control mechanism for the H.264 decoder is designed. It can dramatically improve the stability of the decoder software. Besides, to meet the requirements of a mobile media streaming system, the paper also does research on video and audio format conversion of source media files. A video format conversion software is developed which is able to provide the VoD (Video on Demand) service with various programs. The mobile media streaming system solution on BREW platform can successfully run on China Unicom CDMA2000 1X network and the H.264 decoder can provide high quality VoD service to end users on digital mobile terminals with BREW application execution environment.