Real-time Implementation Of G.729A On VPM642

Nowadays digital speech communication has the highest speed of development and the widest range of applications in the field of information technology. Coding of speech at 8kbit/s algorithm G.729 was based on CS-ACELP. It is one of the most complicated algorithms of speech compression, which uses kinds of advanced technologies in speech coding and compression. G.729 is a very efficient digital coding algorithm which can be applied to many field such as VOIP and net-meeting and etc. G.729Annex A is a reduced complexity 8 kbit/s CS-ACELP speech codec. This annex provides the high level description of a reduced complexity version of the G.729 speech codec. It is bit stream interoperable with the full version. The computational complexity of the G.729Annex A is only one half of that of the full version, with a little loss in the speech quality. Therefore people use the G.729Annex A in the practical projects.The complicated nature of G.729A algorithm and the real-time features of speech communicating put forward high request to the quality of the hardware. Besides, as important component of the communication net, multimedia communication terminal usually integrates many functions such as system-control, image and speech processing and data processing and etc. All of these request powerful ability for the core processor. TMS320DM642 is a fixed DSP processor for the application of multimedia communication, which is produced by the Texas Instruments. Its powerful ability ensures a good hardware foundation for multimedia processing.This paper firstly introduced briefly the general development of speech coding technology. Then stressfully studies the key technologies in the CELP, Such as Linear Predictive Analysis, Vector Quantization, Analysis By Synthesis and etc. On base of these studies and the familiarity of the C source code,made further research on the G.729A codec. After introducing the development of the DSP and CCS3.0 which is the development environment of DSP system, the last part of this paper brought up a method of real-time implementation of G.729A on VPM642. Because the G.729A algorithm is too complicated that it is hard to realize real-time processing. Therefore next we used some code optimization methods such as data packing and etc to improve the efficiency of the codec.The results of test show that these methods can remarkably reduce the computational complexity, thus improved the efficiency of the codec. And the decoded speech signal whose definition and nature characteristic are all good by the method of subjective audition.