| With the development of the multimedia coding techniques, video compression standards have already been successful applied in many fields, such as VCD (MPEG-1), video conference (H.263), DVD (MPEG-2), Set-top Box (MPEG-2) etc. Due to the boost of network bandwidth and the development of high efficient video compression techniques, much attention has been paid on the network digital TV (IPTV) and the streamed multimedia, which are transfer oriented. The boost of network bandwidth promotes the development of streamed multimedia, while the emergence of high efficient video compression standards is the key of the development of the streamed multimedia techniques. MPEG-4 is a compression standard based on the second generation video and audio coding techniques, whose elementary units are video and audio objects. It implements not only the application of digital video, audio and compound graphics, but also the integration of interactive multimedia. At present, it has been widely used in the field like streamed multimedia service. It is believed that XVID is presently the fastest video decoder which follows the MPEG-4 standard. It mainly implements the Simple Profile of the standard. In this thesis a detailed introduction of the decoding process of XVID is presented, which includes algorithm block, algorithm flow and program interface. The newest platform of ADI Blackfin 533 is adopted for DSP implementation. The transplant process, which adopts the assembly language technique, includes the design of the stack, the design of compatible interface and the implementation of each blocks using assemble language. Furthermore, an optimization is made on the level of instruction and system to achieve better decoding performance on the basis of the functionality validation. The optimized XVID ASM decoder has already reached a comparable well performance. Finally, the result of experimentation under ADI platform has approved that the XVID video decoder works correctly and efficiently. |
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