Anyone using FR as a phone?

Jim Morris ml at
Thu Jul 24 23:50:34 CEST 2008

Scott Derrick wrote:
> Come on!  Blame the telcos for the Neo echo!!  Thats stretching it.
> I've had numerous phones and about 4 different providers and NEVER had 
> any repeatable echo, NEVER.

I've done quite a bit of work on VOIP on handhelds, and Echo is always a problem.

The solution was always to buy an echo cancellation library, I say buy because I never have found a 
free one. The problem I found on ARM based handhelds is that they don't have an FPU and usually they 
don't have enough CPU power to do real echo cancellation, so the libraries I have worked with for 
ARM are usually echo suppression, which usually means detecting when someone is talking and dropping 
the output volume (sort of half duplex like those old speaker phones).

I *suspect* that commercial cell phones have H/W echo cancellation built in via a dedicated DSP, but 
there is no way to be sure unless you work for a cell phone company like Motorola, Nokia etc etc.

Landline phones generally do not have echo cancellation built in as the PO does the echo 
cancellation, although higher end speaker phones will have echo cancellation built in.

I think some high end bluetooth headsets have either echo cancellation or echo suppression built in 
which would help in our case.

I do not expect to be able to do echo cancellation on OM because there is no open source echo 
cancellation I am aware of (the Speex codecs may have some) and it is doubtful anyone is prepared to 
write one and make it open source.

Workarounds have been mentioned like using BT headset or tweaking volumes to minimize the echo.

Jim Morris,

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