Call noise on buzz-fixed freerunner with Qtmoko

[Al Johnson]

On Friday 18 June 2010, Peter Mogensen wrote:
> Radek wrote:
>  > You can tweak alsa state in NeoControl application.
> 
> Yeah,.. but I'm ok with editing
> /usr/share/openmoko/scenarios/gsmhandset.state
> for now.
> 
> However... I discovered that NeoControl shows 127 for playback while my
> gsmhandset.state has 110.
> Is it so, that Qtmoko will apply it's own setting (127) temporarily
> every time I make a call and the reason for my noise is feedback to my
> microphone from my speaker?

Depending on what NeoControl does my suggestion below may or may not help.

>  > Echo cancelation is enabled by default. It's hardcoded in modem plugin
>  > and cant be disabled.
> 
> Ahh.. ok.. that explains why I couldn't find where it was defined :)
> 
> Al wrote:
>  > Can you try it yourself to see exactly what the problem sounds like?
>  > My guess  is that your voice is distorted when you're speaking, there
>  > may be some distorted echo when they're speaking, and it doesn't buzz
>  > when nobody's speaking.
> 
> It sound like a lot of electric interference. I hear the other part load
> and clear though.
> 
>  > The recommended setting is just a reasonable starting point. What are
>  > your settings?
> 
> I've included the alsa state file below:

[Snipped all but the 3 important channels, and reordered for the route the 
signal takes]

> 	control.48 {
> 		comment.access 'read write'
> 		comment.type INTEGER
> 		comment.count 1
> 		comment.range '0 - 3'
> 		iface MIXER
> 		name 'Mic2 Capture Volume'
> 		value 3
> 	}
+30dB
> 	control.12 {
> 		comment.access 'read write'
> 		comment.type INTEGER
> 		comment.count 1
> 		comment.range '0 - 7'
> 		iface MIXER
> 		name 'Mono Sidetone Playback Volume'
> 		value 7
> 	}
+6dB
> 	control.5 {
> 		comment.access 'read write'
> 		comment.type INTEGER
> 		comment.count 1
> 		comment.range '0 - 127'
> 		iface MIXER
> 		name 'Mono Playback Volume'
> 		value 110
> 	}
-11dB
Total: +25dB

This is a ridiculous way to get that total gain, unless you want distortion. 
That may be a fine goal on a guitar amp, but not on a phone. For some reason 
it seems to be the recommendation , but don't ask me why. To get the same 
signal level with much less chance of distortion try these:
  Control 48
	value 2 (+24dB)
  Control 12
	value 5 (0dB)
  Control 5
	value 122 (+1dB)