[Community] Is it possible to deactivate the silence suppression on a GTA02 and/or GTA04?

[Radek Polak]

On Tuesday, December 11, 2012 12:04:59 PM Wurzer Juergen wrote:

> Hi!
> 
> Is there a way to deactivate the silence suppression during a phone call on
> a GTA02 and/or on a GTA04? Maybe like setting the level of the voice
> activity detection (VAD) to a minimum, so that it always stays "active"
> and continuously transmit the voice.
> 
> I need this because we have a research project where we embed
> steganographic informations during a call into the voice stream. The
> current problem is that if the audio signal is very quiet (e.g. the person
> doesn't speak) nothing is transmitted because of the silence suppression -
> this leads to the steganographic informations being discarded.

On GTA04 it's possible to do software voice routing - i think in this case the 
sounds will be under your control. If you want to test it, try make a call and 
then select "Speaker" from the context menu. The sound will be then routed by 
program /opt/qtmoko/bin/gsm-voice-routing - source code is here [1]. By 
default it uses speex echo cancellation, but these lines can be commented out 
or you can even replace the program with bash script that calls arecord and 
aplay - see here [2]

> Maybe there are AT commands?
> I have tried to set some AT commands like the ones shown at
> http://wiki.openmoko.org/wiki/Manually_using_GSM on GTA02.

You can stop QtMoko with /etc/init.d/qtmoko-gta04 stop and open and use the 
serial port e.g. with minicom.

Regards

Radek

[1] https://github.com/radekp/gta04-gsm-voice-routing
[2] http://projects.goldelico.com/p/gta04-kernel/page/Wireless/