Abstract:

The MPEG-2 compressed digital video content is being used in a number of products including the DVDs, camcorders, digital TV, and HDTV. The ability to access this widely available MPEG-2 content on low-power end-user devices such as PDAs and mobile phones depends on effective techniques for transcoding the MPEG- 2 content to a more appropriate, low bitrate, video format such as MPEG-4. In this paper we present the software and algorithmic optimizations performed in developing a real time MPEG-2 to MPEG-4 video transcoder. A brief overview of the transcoding architectures is also provided. The transcoder was targeted and optimized for Windows PCs with the Intel Pentium-4 processors. The optimizations performed exploit the SIMD parallelism offered by the Intels Pentium-class processors with MMX support.The optimizations include: 1) generic block-processing optimizations that affected both the MPEG-2 decoder and the MPEG-4 transcoder and 2) optimizations specific to the MPEG-2 video decoder and the MPEG-4 video transcoder. With optimizations, the total time spent by the transcoder was reduced by over 82% with MPEG-2 decoding reduced by over 56% and MPEG-4 transcoding reduced by over 86%.