Optimization Of A MPEG-2 Video Decoder Using The Multimedia Instruction Set Of Godson-2

MPEG-2 video playback is one of the potential target applications for Godson microprocessor series. Early versions of godson-2 are not quite good at this task. Improving MPEG-2 video playback performance is very important for both current and future Godson-based platforms. Newer versions of Godson-2 add multimedia instruction set extension to accelerate multimedia applications.MPEG-2 video playback includes video decoding and displaying. MPEG-2 video decoding composes of sub-procedures such as variable-length code (VLC), anti-scan, anti-quantify, IDCT and motion compensation. On Godson-2 platform, The MPEG-2 video decoding, without any multimedia optimization, occupies about 70 percent of total playback time, at the same time IDCT and motion compensation together occupy about 85 percent of total decoding time.This paper takes an MPEG-2 decoder as example to show the performance improvement of the multimedia instruction set. Firstly, we identify the kernels of that decoder by static program analysis and run-time characters analysis on Godson-2 platform. Then we analysis these kernels in detail, find out their potential data parallelism, and then implement the optimized version for Godson-2. We achieve a speedup of 2.0 for those kernels when running the application and a speedup of 1.4-1.6 for the whole application of MPEG-2 video playback.