9.6 kbit/s ACELP Coding of Wideband Speech

In the recent years, there has been a great advance in the development of speech coding algorithms at very low bit rates. High-quality speech coders are now available at bit rates below 8 kb/s. Researchers’ efforts, however, have focussed on narrow-band speech signals where the transmission bandwidth is limited to 300-3400 Hz, as in analog telephone systems. This bandwidth limitation degrades the speech quality, specially when the speech is to be heard through loudspeakers. For many future applications, a wider bandwidth is needed in order to achieve face-to-face communication quality. A bandwdith of 50-7000 Hz provides significantly improved quality as compared to narrow-band speech. The quality improvements are in terms of increased intelligibilty, naturalness and speaker recognition. Several future applications are foreseen for wideband speech coders, such as teleconferencing, commentary channels, and high-quality wideband telephony.