Hi,

On Mon, Jun 26, 2017 at 11:54:51AM +0100, Mark Brown wrote:
> On Sun, Jun 25, 2017 at 12:48:50PM +0200, Pavel Machek wrote:
> 
> > 2) How to handle GSM audio?
> 
> Do you have some more specific concern?  This already works basically
> fine upstream, we happily support off-SoC audio paths.  The digital
> configuration could do with being more flexible but it works and people
> ship it.  It would be awfully nice to have some control/visibility of
> the modem side but that's just a missing driver problem.

This is not a general problem, but only with the Nokia phones,
which sends raw audio data to the CPU. Nokia's userspace did
postprocessing on DSP and then played the audio via pulseaudio.
As you mentioned this requires a low latency setup of ~20ms.

@Pavel: The Nokia phones are the only ones I'm aware of, that
are implemented this way. Basically all other phones provide
a normal digital audio interface. On those systems you only
have to configure soundcard correctly and will have working
audio.

And as Mark mentioned modern 4G basically uses VoIP, so if some
vendor decides to drop audio handling from modem again it can
simply be done in userspace using normal VoIP application.

-- Sebastian