Fix WebRTC AEC link
You can use any echo canceller (including the one from libspeexdsp) along with Opus.
That being said, among the free acoustic echo cancelers (AEC) we're aware of, the best is probably the Google AEC from the [https://
code. google.com/ p/webrtc/ WebRTC codebase].
=== How do I get the duration of a .opus file? ===