Optimization Of A Low Bitrate Video Coder And Its Implementation On Digital Media Processors

The data of original digital video is very huge, which makes a great challenge for transmission and storage. Video data can be compressed by several decuples, even several hundred folds, which dramatically promotes the development of video communications. Video coders have already become the necessary key components in modern multimedia communication systems. There are several advantages for video coders implemented on digital media processors, which include relatively independent of software and hardware, easily upgradation of firmware, and relatively low cost. They show promising applications in several fields. However, it is urgent to optimize video coding algorithms, so as to implement them on digital media processors in real time.Low bit rates video coding algorithms are studied thoroughly based on analyzing MPEG-4 video coding standard. Based on analyzing characteristics of the architecture of digital media processors, an memory centric optimization design scheme is proposed. Data memory access is very frequently, and the amount of accessed data is very huge in the video coding process, which become the main factor of constraiting the performance of video coders. Motion estimation and text coding process needs more memory resource. By tuning the corresponding algorithms to improve the date locality, so as to form the bit stream based on macroblock in the video coding process. Taking account of the characteristics of memory system of digital media processors, the cache memory is assigned in an optimization mode, simultaously date is transmitted by making full use of EDMA mode. The efficiency of data access is been improved significantly.Based on the above optimized video coding algorithms, a low bit rate video coder is implemented on TI DM642 digital media processor, which partly references XVID open source codes. The optimized video coder can encode the video 10 times fast averagely, comparing with the original video coder. Now, this video coder has been integrated into a real network video surveillance system.