Making teleconferencing a better experience--stereophonic solutions

Yi-Wen Liu $<$jacobliu at stanford$>$ (EE)

This talk is going to be a summary of my work on a stereophonic teleconferencing project at the department of broadband communication services of AT&T Research Labs during the past summer. We believed that although there have been a lot of efforts recently on improving video, the audio quality of commerially available, mono-sound teleconferencing systems is not very good. To build up a sound system devoted to teleconferences, in which many people often need to be able to argue at the same time, we claim that a stereo-sound, full-duplex system is a must.

It turns out that the cancellation of the echoes that arise due to the coupling between multiple loudspeakers and microphones is a mathematically ill-conditioned and hence still unsolved problem. Perceptually, these echoes "enlarge" the conference room and may degrade the speech clarity seriously. We propose a new idea to digitally watermark sounds from different loudspeakers so that the coupling paths from multiple loudspeakers to each of the microphones can be distinguished and the stereophonic echo cancelling problem is reduced to parallel monophonic echo cancelling problems.

A preliminary example of echo cancellation using digital watermarks will be demonstrated and the performance will be evaluated.