Audio devices on Android

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I'm newbie in Android development and I must say, that I'm a little bit confused by its audio framework. I work on porting Android to our custom board and I have almost everything working except of GSM audio.
I suspect that it should be relatively easy to mark some stream as output and some as input for voice calls, but I cannot get into it. I have two PCM interfaces on our SoC, one is used for audio codec and provides speaker and microphone and it is working for me as audio.primary and Android applications can use it. The second one is used for GSM audio interface and I have working it on kernel ALSA level (I can use command line aplay to play and capture sounds). Now I need to connect these two together - to get sound from GSM into speaker and opposite from microphone to GSM.

I think that audio_policy.conf file has to do something with that, but I checked audio.h header and don't know if AUDIO_DEVICE_IN_COMMUNICATION or AUDIO_DEVICE_IN_VOICE_CALL should be used for GSM, what output device, etc.

I know that this description is a bit messed, but I hope that someone can point me to right direction and my question will be clearer then.

posted May 14, 2013 by anonymous

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