Other possible Echo Cause

Paul paultsai at gmail.com
Tue Dec 16 14:35:17 CET 2008

I made the switch to SHR to test out how things are.  The echo problem
is resolved with the following patch


Now there was the annoying buzz to rectify.  This worked perfectly for me.


On Mon, Dec 15, 2008 at 12:21 PM, Al Johnson
<openmoko at mazikeen.demon.co.uk> wrote:
> On Monday 15 December 2008, Paul wrote:
>> > It's possible, but the buzz is within the voice frequency range. If we
>> > could characterise the buzz sufficiently it may be possible to remove it
>> > by applying a suitable digital filter in the CPU, but a hardware fix is
>> > certainly preferable.
>> I was thinking a software noise gate would be preferable since it
>> requires less computing.  Also, anyone tried sound proofing the mic
>> with sound insulating foam to prevent the sound from traveling through
>> the phone?
> There's a noise gate in the Wolfson chip, but I never managed to get it
> working. The functions in the GSM chipset sound like a noise gate in
> operation too. A better low-computing method might be to monitor the GSM
> output and mute the mic if there is significant signal there. This approach
> is used by some VoIP handsets ad is very effective at preventing echo, but
> can be awkward as the other end can't hear when you interrupt them ;-)
> The mic has rubber around it which seals the gap between the mic and the case.
> I haven't tried modifying this.
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Email - paultsai at gmail.com

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