Buzzing on GSM audio

[Timo Jyrinki]

2008/7/26 Andrew Bruno <aeb at qnot.org>:
> FWIW, I've found tweaking these specific settings in
> /usr/share/openmoko/scenarios/gsmhandset.state effect the intensity of the
> buzzing sound. Specifically:
>
>  * 'Mono Playback Volume'   (85)
>  * 'Mono Sidetone Playback Volume'  (7)
>  * 'Mic2 Capture Volume'     (3)
(buzz)
...
>  * 'Speaker Playback Volume'  (112)
>  * 'Bypass Playback Volume'    (7)
(echo)

Thanks! With these tweaks to my current settings, I've successfully
for the first time received a confirmation that the receiver of my
call didn't hear an echo of her own voice.

However, I did tweak "Mono Sidetone Playback Volume" from 7 to 4,
since in my own testings with two phones I heard quite a lot of buzz
still. That lessened it, and the receiver seemed to hear my well
enough anyway.

My paranoid / not-knowing-what-I-do procedure is to:
1. change /usr/share/openmoko/scenarios/gsmhandset.state
2. alsactl -f /usr/share/openmoko/scenarios/gsmhandset.state restore
3. alsactl -f /etc/asound.state store
4. reboot

I now added a link to your post at
http://wiki.openmoko.org/wiki/Freerunner_Hardware_Issues#Poor_Audio_Quality
since this is the first time I really achieved some good results.

-Timo