Reduce volume of speaker to zero during a GSM call

[Fedor Lyakhov]

Hello,

I'm working on a feature for Android ROM (based on 4.x at the moment) that would allow reducing volume of the speaker to zero during a GSM call. Normally, it isn't possible to reduce this volume less than some level. I need to be able to control this, i.e. be able to set this level to zero for some calls. Could anyone point me to the right place where this threshold is actually implemented? I've been looking through AudioService, AudioSystem, AudioPolicySystem and few other places - and didn't find anything related to it.

Thanks,
Fedor