Low rate speech coding for telecommunications

Over the last decade major advances have been made in speech coding technology which is now widely used in international, digital mobile and satellite networks. The most recent techniques permit telephone network quality speech transmission at 8 kbit/s, but there are still demands for even lower rates and more flexible, good quality coding techniques for various network applications. This paper reviews the developments so far, and describes a new class of speech coding methods known as speech interpolation coding which has the potential to provide toll-quality speech coding at or below 4 kbit/s.