Showing papers on "Adaptive Multi-Rate audio codec published in 1985"
TL;DR: A hybrid digital audio codec based on deltamodulation has been developed as an alternative to PCM and offers high quality audio performance at overall bit rates of 250-350 kb/s/channel.
Abstract: A hybrid digital audio codec based on deltamodulation has been developed as an alternative to PCM. System gain and emphasis are dynamically variable under control of a sophisticated companding algorithm; separate control bit-streams are generated for subsequent transmission to the decoder. The system offers high quality audio performance at overall bit rates of 250-350 kb/s/channel.
6 citations
NEC1
TL;DR: A full-duplex 16 or 9.6 k bits/sec speech codec based on the multi-pulse excited LPC coding technique has been developed and reconstructed speech was quite natural and almost undiscernible from original speech.
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. Signal to noise power ratio for a sine wave signal was 30 dB at 16 k bits/sec.
2 citations