Stereophonic acoustic echo cancellation system using time-varying all-pass filtering for signal decorrelation

This paper describes a novel technique for decorrelating the stereo signals in stereophonic acoustic echo cancellation (AEC) systems. At present, most teleconferencing systems use a single full-duplex audio channel for voice communications. However, in order to introduce spatial realism, future teleconferencing systems are expected to have more than one channel (at least stereo with two channels). However, in stereophonic AEC systems, the correlation between the stereo signals does not allow correct identification of the echo path responses. In this paper, we develop a signal decorrelation technique based on time-varying all-pass filtering of the individual stereo signals. Experiments show that this technique does not effect the perception of the stereo signals, but identifies the echo path responses correctly.