Research And Implementation Of G.729Speech Coding Algorithm Based On DSP

G.729(Conjugate Structure-Algebraic Code Excited Linear Prediction,CS-ACELP) is standard of telephone bandwidth speech coding, and its coding rate is8kbps. The algorithm has a good sound quality in this rate, therefore it is used widelyto mobile communication standard, IP(internet protocol) telephone and all sorts ofterminals. However, the large computation complexity of the algorithm and therequirements of real-time put forward high demands to hardware. Digital signalprocessing technology has been rapidly improved with the development of hardwaretechnology in recent years. The appearance of digital signal processor (DSP, DigitalSignal Processor) made it possible to implement G.729algorithm on hardwareplatform. DSP is the best tool for speech processing because of the fast processingspeed, low power consumption and strong operation ability.In this thesis, the theory of G.729algorithm and the relevant technology of G.729speech codec based on DSP are discussed in detail. The optimization schemes ofopen-loop pitch analysis and simplification to gain quantization operation areproposed. The two optimization schemes are verified by MATLAB simulation. Thesimulation results demonstrated that the proposed schemes are correct and effective.In summary, the main achievements and conclusions in this thesis are shown asfollows:(1) An optimization scheme of open-loop pitch analysis based on combination ofthree level clipping and coarse searching is proposed. At the same time, a simplifiedgain quantization operation scheme is proposed. The two optimization schemescontribute to reducing the amount of calculation of open-loop pitch analysis and gainquantization operation without loosing quality of speech basically. In this thesis wesimulate the two optimization schemes via MATLAB. Simulation results demonstratethat the optimization scheme of open-loop pitch analysis and simplified gainquantization operation are effective.(2) The optimization schemes of code, compiler and function are proposed. Theschemes improve the execution efficiency of the program in the context of normaloperation of the G.729algorithm in hardware. The comparison table of the amount ofrequired computation is acquired via the implementation of G.729based on DSP. Thetable elaborates the comparison of speech coding part before and after optimization.The experiment results show that this optimization scheme is feasible and effective.At the same time, it demonstrates that open-loop pitch analysis and simplified gainquantization operation are also effective in the realization on hardware platform. (3) The design scheme of G.729speech codec based on TMS320VC5509A iscompleted. This scheme consists of the hardware and software. The hardware designprocess and the realization process of software are described in detail so that real timeimplementation scheme of G.729algorithm based on TMS320VC5509A is well done.The results show that the hardware and software design of this algorithm are stableand reasonable.In conclusion, the research and implementation of G.729speech codingalgorithm have received wide attention in the speech processing field. It will generatea positive affect on speech processing, information science, hardware developmentand other fields.