Multi-speaker conferencing over narrowband channels

A technique for digital conferencing over narrowband channels which allows for the representation of multiple simultaneous speakers is proposed. The technique takes advantage of the properties of multirate parametric vocoders (which includes the sinusoidal transform coder and the multiband excitation vocoder, as well as embedded coders). The technique performs signal summation in a manner similar to analog conferences; however, signal summation is deferred to the terminal. To maintain quality for a single speaker while allowing multiple speakers, the technique adaptively allocates channel bandwidth based on the number of speakers to be represented. Development is in progress on a system that allows two simultaneous speakers, although a system for three simultaneous speakers is achievable