Recurring Echos in BBB-Conference

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Ferdinand Soethe

Jan 15, 2021, 7:04:55 AM1/15/21
to bigbluebutton-users
In todays BBB conference I experienced a unusual number of problems with
echos in my voice stream.

This usually happens once in a while and is fixable by disconnecting and
-reconnecting the audio.
Same today, but the echo re-occurred at least 5 times in a 4h conference
and it made me wonder, why this happends and how we can prevent that.

It doesn't seem to be caused by the headset because it also happends
with another microphone.

Kind regards

Reimar Bauer

Jan 15, 2021, 7:19:51 AM1/15/21
occasionally I have something like this also on my linux client.
Sometimes I have Pulse and also Alsa audio together.
I've not understood what creates this multiple audio devices. When
they are present I hear myself all time.
Is that also how it behaves on your computer?

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Jan 15, 2021, 9:17:31 AM1/15/21
So when you hear echo... look at the talking indicators of the other users, and see which ones pulsate when "you" talk.. your voice is coming back thru their mics.

AEC echo cancellation works on all the users clients and tries to cancel your voice coming out of other speakers so it doesn’t enter back into the users mic and into the conference.

Easiest fix is just mute the offender and echo disappears.

So why does this happen? The echo cancellation has a buffer to try and handle jitter and do its job.... if some of your users are on lossy network connections, and the jitter is > 160ms, the echo canceller loses it sync, and has to retrain. The jitter was larger then the browser buffer. (not selectable yet in browsers)

Also if a phone joins in by telephone call, and it is on speakphone, the same thing can happen if it does not have AEC built into the phone device.

You often will notice when a user joins, you hear echo for just a second then AEC kicks in and does its job...


Jan 16, 2021, 5:53:44 AM1/16/21
to bigbluebutton-users
Thank you Stephen for your very detailed explanation. That helps a lot explaining these specific situations and will save me a lot of hassle reconnecting my own microphone :-)
Kind regards

Jan 16, 2021, 9:21:21 AM1/16/21
to bigbluebutton-users
For German language users, I have incorporated Stephens Information into this article.
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