Stereo Acoustic Echo Cancellation (AEC) software is required for conferencing applications which can mix independent audio streams for the left and right loudspeakers.  For example, if you want to reproduce the spatial feel of a live conversation, you can assign participants to the left or right loudspeaker channels. The loudspeaker’s will have their own signal and their own echo impulse response back to the microphone.  Thus, two independent adaptive filters should be applied to the microphone signal to remove the acoustic echoes.

stereo acoustic echo cancellation conferencing block diagram Echo Cancellation for Conferencing

A stereo AEC solution must also be applied in systems which apply a time varying panning of a mono signal.  The panning changes the contribution of each impulse response of the system and must be tracked with two filters.

Some conferencing solutions may try to mix the left and right channels into a mono signal for a mono AEC.  This will significantly degrade the echo return loss enhancement.  Only a stereo AEC solution can provide the best performance.