Research And Implementation On Speech Encoding For Distributed Phone Scheduling System Based On DSP

In recent years, with the rapid development of communication technology, thecompression of speech coding technology has also made breakthrough progress. Inorder to satisfy the growing needs of intense bandwidth demand, a series ofinternational data compression standards have wide applications, and some encodingtechniques at low rate or middle rate have been standardized and industrialized. The fastdevelopment in speech communication field such as VOIP, multimedia communication,mobile speech communication and ISDN results in higher requirements for speechcompression codec technology. At present, the research of real-time implement withG.728and G.729algorithm is getting more prevalent.In accordance with conjunction structural algebra code exciting linear prediction,the G.729algorithm has been widely used in speech signal processing. The synthesizedspeech with good quality, low bit rate and time delay can be applied in many fields suchas speech storage and transmission. However, the high algorithm complexity withG.729results in difficulty of real-time implement. Owing to the advantage of DSPtechnology, the DSP chips with low-price, low-consumption and high-performance canefficiently solve the problem mentioned above. Meanwhile, in accordance with G.729algorithm, there also needs plenty of optimization based on DSP hardware system so asto realize signal compression in real-time processing.The task is one portion of distributed phone scheduling system based on CAN bus.The target is to develop a speech compression system according to ITU-Trecommendation G.729, and the key hardware of the system is Texas Instruments ofTMS320VC5502. Speech frames are captured through a telephone and transformed intodigital signal by an audio A/D converter. The data streams are encoded inTMS320VC5502in according to G.729algorithm and the output data is in bit steamformat. Through the interface device, the data streams are transmitted to the receiver.Finally the bit streams will be decoded and converted into synthesized speech signal.The paper introduces server prevalent standards of speech compression anddiscusses some principle theory about acoustic signal processing. Through studying andanalyzing the basic theory of G.729algorithm, the task mainly concentrates on theoptimization of real-time implement, including algorithm optimization, compileroptimization, C language optimization, and assembler language optimization. The experiment through code profiler shows that the speech compression system based onimproved G.729program can encode and decode the speech signal in real time. TheMOS score of the synthetic speech can achieve basic requirements of normal voicecommunication which has a high quality and gets good performance.The distributed phone scheduling system based on CAN bus can be widely used innetwork audio video signal transmission, video conference etc. As an important part ofthe system, the speech compression module can also be applied in IP telephone andother speech communication systems, which has special reference and practical values.