Studying And Implementation Of ITU-T G.729A

With the rapid development of computer, wideband network and IC technology, the information network mainly basing on multimedia communication becomes the world's hotspot. Especially, the great success of Internet makes IP become the backbone technology of the future information network. And the successful development and application of IP telephony foreshow the appearance of the new information network basing on IP.IP telephony is an integrated technology, which involves with computer network, signaling protocol, digital signal processing, etc. And the digital signal processing mostly is the speech signal processing that is the encoding and decoding of the speech signal. For the encoding and decoding schemes of IP speech signal, ITU-T has worked out the serial recommendations such as G.711, G.722, G.723.1, G.728, G.729, and so on.This thesis mainly studied the recommendation G.729 and its annex A (G.729A) among the above recommendations.The characteristics of G.729 were contrasted with the most speech signal coding recommendations at first, and then analyzed the characteristics, analysis methods, mathematical models and different speech signal coding schemes. Following it, the algorithms of G.729 and G.729A were studied, and also contrasted in order to show how the CS-ACELP algorithms are simplified in G.729A. At the following chapter, the fixed point ANSC C simulation programs G.729A was analyzed and studied using VC++6.0, and great emphasis was put on the functions and algorithms. At the end of the thesis, the research actuality of the improving schemes of the coding of speech signal inside and outside the country were summarized, and brought forward the suggestion that it can improve the coding algorithm of the speech signal by improving the quality of speech signal and shortening the delay of the algorithm. Then an improving implementation scheme of fast searching for the codebook of G.729A was bring forward, In which, the sequence of codebook search is reordered according to the criterion of mean squared weighted error between target vector and filtered adaptive codebook vector, and the algebraic codebook is searched until a predetermined threshold is satisfied.