The Research On G.729 Speech Code Algorithm And Application In DSP

In recent decades, the technology of the speech code is developed very fast. Take telephone-bandwidth as an example, Since putting out the 64kb/s PCM speech code international standard in the 20th century 70's, CCITT has already put out such international standards as 32kb/s ADPCM , 16kb/s LD-CELP , 8kb/s CS-ACELP , etc . in succession. CS-ACELP standard is also called the Recommendation G.729, which adopt kinds of advanced technology of the speech code nowadays, is the most complicated in the speech code standard recommended in CCITT. Its application is very extensive, for instance VoIP, the videophone and telecomference, etc.Firse of all, several kinds of the most important technology of the speech code has been introduced in this paper, for instance Short Time Process, Linear Predition Analyse, Vector Quantization, Analyse by Synthesize, etc. On the basis of carrying on futher investigation on these technology, this paper have carried on the analysis and research to the algorithm further. On this basis, this paper attempt to hold the mentality of designing of the algorithm, and analyse and study the algorithm source code that ITU offer, and carry on emulation and prove it. Emulation shows that though the compression of the algorithm is higher (16: 1), but the data after the decode are essentially identical with data before the code, and listen to the sound subjectively has no difference. In addition, emulation also shows that the code is unable to run in real-time.And then, this paper has carried on feasibility research to realize the algorithm on the TMS320C54x DSP of TI Company, has summarized and proposed some methods to optimize the code, for instance use the optimizer to optimize the code, change the procedure with low operational efficiency into assembler, write the program based on the structure of the hardware, etc. Emulation shows that the operational efficiency of the procedure improve quickly with these method, and that it is possible to realize algorithms on the TMS320C54x DSP.Finally, this paper put forward the method to optimize code: write code on the basis of superscale, dispose the memory rationally, adopt circulation—expand technology, simplify the algorithms, etc.