High-Quality Coding of Telephone Speech and Wideband Audio

Advances in digital signal processing have helped us to realize sophisticated technologies for speech communication in cellular radio and ISDN. For traditional telephony, characterized by a signal bandwidth of about 3.2 kHz, the transmission rate for network quality is now down to 16 kbps, with the prospect of a new CCITT standard. Robust communications quality appropriate for cellular radio has been realized at 8 kbps. Research attention is now shifting towards 4 kbps, with focus on increasing the already decent levels of naturalness and speaker identification.