MPEG-4 Video Decoder Realization Based On Davinci Platform

The multimedia technology provides an important information source for human vision. But the limited bandwidth restricts its development. Over the past few decades, video compression technology had proved to be a good solution to break this bottleneck. MPEG-4 is widely recognized as the outstanding video standard of compression technology now.In the mean time, with the developing of DSP’s processing ability, it provides a stick hardware foundation for the complex computing in video image’s coding and decoding. In this paper, we have combined both of these advantages and transplanted Xvid Decoder, which is based on MPEG-4 to the TMS320C6474 multimedia processing platform. For reaching the requirement of real-time decoding 720P (1280x720), we have further optimized the system.The main task is divided into the following sections:Firstly We have deeply read up the MPEG-4 and H.26x standards and implemented the de/coding model.On the basis of various video algorithms and common compression framework, we have paid great attention to Xvid Codec, highly focused on texture decoding and motion compensation, and verified the function of Xvid Codec with C code under the PC environment and implemented the model which will provides coded source file for the DSP decoder.Secondly, we have separated the encoder from the codec after functional verification. Aiming to adapt to the DSP’ further development, the thesis have deleted the GMC (Global Motion Compensation) and some other features, streamlined debugging information and time measurement function, and modified part of data structure. In addition, we have detected assembler statements for X86 PC to reduce the code size.Finally, we have taken an optimization in TMS320C6474 multimedia platform. According to the memory feature in TMS320C6474 and memory assumption in decoding process, we have assigned the proper memory on chip, Then analyzed the operating performance with the code analysis tool and measured different parts with different methods:IMG LIB assembly library functions for IDCT(Inverse Discrete Cosine Transform); inline functions for complex C statements; Cache and EDMA for data transfer. At last, we have configured the various compiler optimization options, and modified the internal loop to fit the water directive.The multimedia test results showed that the Xvid DSP decoder can decode 32.19 frames MPEG-4 720P video per second on average.