I want to use Echo cancellation for my Skype calls and Empathy on Ubuntu 12.10 (pulseaudio 2.1). Anyone knows how to do that?
Skype handles echo itself, so this is not handled by PulseAudio. Empathy has a tick-box in preferences to enable echo cancellation, which will then make it tell PulseAudio to take the appropriate steps to enable AEC. Ideally, things should just work out of the box.
By default, PulseAudio will try to use the webrtc canceller which is pretty good. Unfortunately the 12.10 pulseaudio package does not use this. It will use the speex canceller which is reasonably good. I believe that enabling support for the webrtc engine is something being considered for the next Ubuntu release.