Research On Optimal Design And Implementation Of Real-time G723.1 Coder In Fixed-point DSP

In the times when Internet quickly popularizes in the world, VOIP has more and more received people's attention, and video conference system based on H323 also is beginning to be implement in big company for IP network can provide the speech service of good quality and the low cost of communication. The question, still faced by the existing network resources though there are several low bit-rate speech code algorithm, is that the current technology should communicate the speech data of high quality in the extremely low rate. In the present algorithm, G.723.1 provides the lowest rate and the reconstruction pronunciation of high quality. So the application value of G.723.1 will be inestimable. The algorithm principle of G.723.1, and the hardware characteristic and the instructions set of Blackfin533 which is the ADI Corporation's fixed-point DSP chip are introduced in the paper. We then discussed the implement of G.723.1 speech coder on fix-point DSP chip Blackfin533, in the background of the H323 videophone system development. This paper provide the scheme of the real-time implement of G.723.1 with the fixed-point way entire assembly in the Blackfin533 hardware environment, and discussed with emphasis in the optimized strategy and key technology of designing with fixed-point C language and assembly program. After the optimization the performance of G.723.1 encoder satisfies the real-time request at the few hardware resources cost. The encoder saved enough spaces for the video frequency code and other module in H323 system. According to the experimental result, the G.723.1 encoder can provide the reconstructive speech of good quality under real-time condition, and pass all ITU-T G.723.1 test vector. By the way, the G.723.1 encoder already applied in the product development of H323 videophone system.