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WebRTC Opus stereo downmixed to mono

Hi Everyone,

I’m trying to publish and play a canvas of videos and audios. I’ve succeeded for most of it, the only issue i got is that some of the audio tracks are played only on the left speaker but when I publish and play it back, my left speaker tracks are played on both left and right speakers…

It means that at some point between publish and play audio stereo tracks are downmixed to mono.

I’ve tried to apply constraints to audio tracks (echoCancellation, autoGainControl, noiseSuppression), add “stereo=1;sprop-stereo=1” to my “a=fmtp” sdp line, which are supposed to ensure stereo playback, but with no effect…

Does anyone have a clue of what can be wrong ?

When using Opus as the audio codec in WebRTC. it must be forced to the stereo setting. I can direct you to the documentation and code for this, but if you still have issues, please do submit a support ticket so we can see why it’s behaving that way.

Configure the audio stream source for stereo. I

If your source isn’t configured to send stereo audio, in the Decode/Audio container, set the default.scaleChannels parameter to 2 to force any mono audio frames to stereo by duplicating the mono stream for both the left and right channels.


Customers can set a Transcoder decode to force stereo with the property described here in this doc: