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Re: [Linphone-developers] improving AEC on the Pi

From: Ghislain MARY
Subject: Re: [Linphone-developers] improving AEC on the Pi
Date: Tue, 07 Jul 2015 15:39:50 +0200
User-agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

Hi Mark,

Speex does not only provide a codec but also some signal processing functions such as an echo canceller.
The codec you are using, be it G722 or any other ones do not affect the speex echo canceller.
At some point in time the echo canceller state was directly stored in the linphonerc file so you can also check if you have a big blob of unreadable characters in the [sound] section of your linphonerc file (probably named ecstate).
How did you get Linphone on your raspberry?


Le 07/07/2015 13:34, Mark Eastwood a écrit :
Hi Mary,

Thanks so much for the response.

I’ m using the G722 codec for linphone. Does this affect whether the Speex echo canceller is used and ecstate is saved? Should I be choosing a Speex audio codec to gain these benefits?

I don’t believe I’ve downloaded your speex repository. Is it easy to install and ensure Linphone uses it on the Pi?  Note I don’t have the .linphone.ecstate file saved after each call.

br, Mark


The speex echo canceller is quite long to converge. It's the reason why 
we have our own repository for speex with changes to save and restore 
the echo canceller state.
To check if this is enabled in your case, look for a .linphone.ecstate 
file next to your linphonerc file after a call. If it's there the echo 
canceller should converge quite fast.
Otherwise the Linphone you are running may be using the "standard" speex 
library and there's not much to be done.


Le 02/07/2015 22:13, Mark Eastwood a ?crit :
I?m using two RPi to communicate as speakerphones using the Linphone SIP clients and despite tuning the echo parameters exhaustively I still get quite a lot of echo for the first several seconds of a call - I?m driving the speaker quite loud and also want maximum microphone sensitivity (Alsamixer levels set around 82 each) which isn?t ideal for reducing echo.  I?m struggling to make further improvements using the .linphonerc file parameters and wondered if anyone has additional suggestions for how I might reduce this initial echo. Are there additional parameters I can play with somewhere?

Many thanks for any help,

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