First International Conference on Spoken Language Processing (ICSLP 90)
The prospect of multi-channel/multi-user speech communication via the emerging ISDN has raised a lot of interest in advanced coding algorithms for 7KHz wideband speech. The capability of 32Kb/s wideband speech coding will support sustained high-quality stereo (or bilingual) voice transmission for audio-video teleconferencing over a basic rate 64Kb/s ISDN channel. In addition to the high-quality requirement, network applications are likely to dictate the use of algorithms with a very short coding delay. This paper reports on the use of the well known Codebook Excited Linear Predictive (CELP) [1»3] algorithm for 32Kb/s low-delay (LD-CELP) coding of wideband speech. The main problem associated with wideband coding, namely, spectral noise weighting, is discussed. The paper proposes an enhanced noise weighting technique and demonstrates its efficiency via subjective listening tests. In these tests, involving 20 listeners and 8 test sentences, the average ratings for the proposed 32Kb/s LD-CELP was essentially equal to that of the 64Kb/s standard (G.722) CCITT wideband coder.
Bibliographic reference. Shoham, Yair / Ordentlich, Erik (1990): "Low-delay code-excited linear-predictive coding of wideband speech at 32 kbps", In ICSLP-1990, 117-120.