Research And Design Of G.729 Speech Coding System Based On BF533

Speech coding is one of the key technologies in the area of digital speech communication. Over the past 20 years,with the high-speed development in the fixed line phone and mobile communications,the theory and technology of speech compression coding have made great progress,and are widely used in lots of fields.In a variety of the present speech coding schemes, CELP(Code-Excited Linear Prediction) has become one of the most important and most successful speech coding techniques.In 1996,ITU-T published G.729 speech coding protocol, which using CS-ACELP(Conjugate Structure Algebraic Code-Excited Linear Prediction) coding algorithm.Although CS-ACELP is based on CELP coding model,but overcomes many defects, such as high computational complexity and large storage space.Currently,CE-ACELP is an ideal coding algorithm,and provides us with low bit rate,high-quality and low latency speech compression coding.In 1982,the first DSP chip was put out,and followed by a rapid development,which laid a solid foundation for the implementation and application of speech encoder.Now,because all kinds of general-purpose DSP chips have come into use,which have high working speed,high performance,but low price,and low power cost.Various kinds of new speech coding algorithms and theories have come out of the areas of computer simulation,and are put into practical use. ADSP-BF533,which is used in this paper,is a highly cost-effective DSP chip,and is very suitable for the real-time implementation of many voice coding standards recommended by ITU-T,including G.729.Firstly,this paper introduces the basic theory of the current mainstream speech coding technology,then particularly studys the basic principle of G.729 speech coding algorithm,and improves some key modules,such as adaptive-codebook and fixed-codebook,aiming to reduce the computational complexity of the G.729 algorithm.Secondly,it briefly reviews the theoretical and engineering knowledge of DSP chip,and put emphasis on the technology and characteristics of Blackfin family DSP chip,produced by ADI Company,then it study the inner structure and the various peripheral interfaces of the ADSP-BF533 chip.Next,it puts forward a whole scheme for the speech coding system,including hardware system design and software system design,and on the basis of the ADSP-BF533 EZ-kit Lite Desktop Evaluation Kit.Thirdly,it completes the transplantation of C source code to the evaluation board,and optimizes the original code according to the study and the application of optimizing strategy.The result show that the optimization of the source code improves the encoding speed by 13 times.Finally,the Matlab simulation test proves the correctness of the optimized code.