Please help to clarify when %Nxxxx settings got reset

Al Johnson openmoko at
Wed Jan 7 23:15:25 CET 2009

On Wednesday 07 January 2009, Dieter Spaar wrote:
> Hello Pavel,
> > As far as i can see for most people %Nxxxx commands are absolutely
> > necessary to get a loud and clear sound (especially on remote side)
> > without echo during voice conversation.
> >
> > We now know all the possible values but some people got mixed results
> > with these settings because they're somehow got reset to "No echo
> > suppression and noise cancellation". Some say they have to re-issue %N
> > commands after every incoming call.
> >
> > I hope you're the one who can say exactly when it's best to issue
> > those commands to ensure an acceptable sound quality :)
> I am sorry to say that I cannot answer this, simply because
>  I don't know it without spending probably quite some time
> on trying to find out the details. The problem is that the
> actual work is done by the DSP inside the Calypso. Besides
> that Openmoko has only a very small part of the GSM source
> code, we do not have any information about the details going
> on in the DSP.

Is this something that a volunteer who's signed the NDA would be able to look 
into? If we're lucky here might be something in the small bit of GSM source 
OM do have access to.

> Just a question: Would it be a problem to re-issue the command
> every time before or after after accepting a call ? Isn't it possible
> to integrate this command into the application which take care
> of accepting the phone calls ? If this is an essential command, there
> should be a setting for it, similar to adjusting the volume of the
> speaker.

I believe this workaround has been in the 2008.x qtopia-based phone app for a 
while, and has been proposed (including patch) for FSO. It would be good to 
have some information about how the various settings work, but if it's not 
possible we'll have to work with the little we have.

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