New directions in low bit rate speech coding

It is pointed out that impressive progress has been made during recent years in coding speech with high quality at low bit rates and at low cost. The new digital cellular system in North America is using coded speech at 8 kb/s, but much lower bit rates are needed to support the increasing demand for cellular telephones. It is noted that incremental changes in the present technology are unlikely to produce high-quality speech at very low bit rates. Current research at Bell Laboratories is aimed at creating new representations of speech, both in frequency and time, to allow for efficient coding of speech information. The author reviews the key ideas that support the present speech coding technology and discusses some of the promising new directions