Correlative Technology Of Modern Speech Coding And Its Dsp Implementation

In the past few decades, speech coding technology has been developing continuously. Except simple coding in modern speech coding technology, there is a serial of technology to solve transmitting medium and surrounding problems.With the development of digital signal processing technology, the application of DSP is more and more extensive. Now, almost every hand-equipment has one DSP chip.The correlative technology of modern speech coding and its DSP implementation are presented in this paper. It is possible that speech frame will be lost in network transmitting. Packet Loss Concealment technology can compensate that. Firstly, several kinds of Packet Loss Concealment technology are discussed in this paper. Then the realization of Packet Loss Concealment algorithm recommended by G.711 on TMS320C55x is described. Secondly, open-loop pitch analysis module of G.729 is taken as an example among many speech coding modules. The module's optimization on 5416DSK board is also introduced and its result is given. Voice Activity Detection (VAD) may save valuable resource of transmitting bandwidth. It will be in favor of reducing delay that user feels. If one call has a long time silence, it will make user feel not well. Comfort Noise Generator (CNG) is that sender sends a few frames in silent time and receiver generates comfortable background noise using those frames. Finally, the feasibility of VAD/CNG parameters being transformed directly between G.723.1 and G.729 is discussed in this paper. The transform scheme and its implementation on C55x are presented too.