A multi-pulse LPC speech codec using digital signal processors

Abstract

A full-duplex 16 or 9.6 k bits/sec speech codec based on the multi-pulse excited LPC coding technique has been developed. Cross-correlation analysis was used for the pulse search method. The codec was implemented by using five NEC 7720 Digital Signal Processor LSI chips ; four DSPs for the coder and one DSP for the decoder. A general purpose microprocessor was also used for system control.Reconstructed speech was quite natural and almost undiscernible from original speech at 16 k bits/sec and still quite good at 9.6 k bits/sec.

Analysis of ECG by multipulse excited linear prediction model

“…the Q and S waves were recon structed very weIl. The method can be implemented in real time, using DSP hard ware as mentioned in [3]. Authors are presently engaged in extending the method for analysis of multichannel ECG and stu dying the effect OIf quantization of pulse amplitudes on the quality of the repro duced signal.…”

Técnicas para Excitação em Codificadores de Voz do Tipo LPC

“…Uma forma alternativa para representar CJ.j0p e €j é em termos da seqüência de ccrrelação cruzada [7], (8…”

Fully vector-quantized multipulse LPC at 4800 bps

“…An improved classifier utilizing the remaining bits and a technique for reducing the boundary effect may lead to a 4800 bps high quality MP-LPC coder for applications such as mobile radio or voice mail. Since an MP-LPC coder using a crosscorrelation for pulse search has been realized in a real-time system[8] and a real-time speech coder using vector quantization with a codebook size of 256 has already been implemented using a relatively primitive 4js VLSI chip[9], it seems clear that implementation of the coder proposed here is well within the capabilities of today's technology.…”