Design And Implementation Of Digital Recording System Based On G.729

Recently, DSP has been the basic devices widely used in communications, computer science, and consumer electronics. DSP technology has been a powerful tool especially in speech signal processing, and it makes it possible for us to real-time implement all kinds of complex algorithm. ITU-T Recommendation G.729 was approved in 1996 containing the description of an algorithm for the coding of speech signals at 8 kb/s using Conjugate-Structure Algebraic-Code-Excited Linear-Prediction (CS-ACELP), and it is widely used in multimedia communications, cell mobile communications and IP net phone. The CS-ACELP coder is based on the Code-Excited Linear-Prediction (CELP) coding model consisting of several key points such as Linear Prediction Coding analysis, Vector Quantization, Conjugate-Structure Algebraic-Codebook, Perceptual Weighing, and so on. This coder is designed to operate with a digital signal obtained by first performing telephone bandwidth filtering (Recommendation G.712) of the analogue input signal, then sampling it at 8000 Hz, followed by conversion to 16-bit linear PCM for the input to the encoder. The output of the decoder should be converted back to an analogue signal by similar means. In this thesis, Recommendation G.729 is detail discussed, emphasizing on optimization of Coder and Decoder, and realized in assembly language on single DSP, based on all of above, a digital recording system is designed and implemented, the core of which is the fixed-point DSP TMS320C5402 of Texas Instruments, A/D convertor and external FLASH memory also plused. Now the prospective basic function such as recording and retrieving has been realized on testing board. Informal subjective quality test indicates that the speech quality implemented on the fixed-point DSP achieves the standard of G.729 at 8 - II -Abstractkb/s with good extent of naturalness and definition. This recording system is valuable in practical usage for the speech signal can be recorded and retrieved conveniently on one independent board.