[om2009-r4] Warren's Settings Worked for Me (was Re: Om2009 testing release 4)

Joerg Reisenweber joerg at openmoko.org
Mon Jun 8 16:27:42 CEST 2009

Am Mo  8. Juni 2009 schrieb openmoko at humilis.net:
> Joerg Reisenweber wrote (ao):
> > Am Do  4. Juni 2009 schrieb William Ray Yeager:
> > > A critical friend of mine who has mocked my purchase of an
> > > "unfinished" phone just told me that our connection was as good as a
> > > landline!  I followed Warren's advice below and lowered control.5 to
> > > 80 (I'm naturally conservative) which has (so far) completely removed
> > > the previously unbearable buzz my friend had observed on the other end
> > > of the conversation.  Wow.  Now I might not need to solder in a new
> > > capacitor!
> > > 
> > > For the demi-newbie:
> > > 
> > > Open /usr/share/openmoko/scenarios/gsmhandset.state
> > > Scroll down to control.5 and in that section change the line under
> > > 'Mono Playback Volume' from "value 110" to "value 80".
> > > Save file.
> > > Call OM skeptic.
> > > Gloat.
> > > 
> > > Warren said:
> > > 
> > > "I've always had people complain that they got a lot of static when
> > > they called me - I thought I had the buzz problem in fact.   I just
> > > spent the time to figure out how to use alsamixer to tweak things, and
> > > if I set control.5 (Mono Playback Volume)  to 83 from above 100 like
> > > I've seen in other gsmhandset.state files (ranging from 100 to 110
> > > seems normal), I get a perfectly clear signal on the other end."
> > 
> > Another unconfirmed taletelling about Buzzfix by ALSA settings. Don't you 
> > think we checked this prior to coming up with a hw-rework after months and 
> > months of wrestling with this issue?
> Joerg, I also tested this by lowering Mono to 72 with alsa-mixer on my
> A6 OM2009 Test4 after reading Warrens mail, and I now no longer sound
> like sitting on a motor lawnmower during a call.
> Maybe this is something different than the Buzz Issue, but it improves
> sounds for the other party a lot.
> This btw is in The Netherlands. After reading that less than 5% of the
> owners are hit in practice by the Buzz Issue, I was pretty surprised to
> be one of them. But now it seems the noise is not due to the Buzz Issue?

reducing mic gain and/or mic volume might cause some of the many sound 
improvement circuits involved in carriers' exchange (here: half duplex echo 
cancellation, kind of a two-way noise gate) to cut out buzz during periods of 
no voice transmitted. Nevertheless the S/N ratio *during talking* (S=your 
voice, N=buzz) can NOT be changed by alsa settings any way whatsoever.
So this change of control.5 may improve some of the subjective audio sensation 
for far end, only if you got slight buzz that becomes unnoticeable during 
actual voice. Severe buzz rendering voice illegible can NOT be cured this 
way, not even a little bit.
btw you can get same result (without lowering volume of your voice for far 
end, and without relying on carrier's/far-end's EC meassures) by setting 
AT%Nxxxx noise gate value of Calypso to a level that effectively stops buzz 
during periods of no voice (aka silence)

Official recommendation is: If you got Buzz issue, try to get bigC-buzzfix.

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