Hello Andreas,
sorry for late response.
I set up a network with Virtual Um and multiple OsmocomBB phones. They register, they can send and receive SMS and I wanted to try voice calls.
First of all, it should be noted that voice support in OsmocomBB is experimental and undocumented. I have been working on GAPK back-end integration, and it seems you've already found some branch, but I would recommend to use 'fixeria/audio' instead of 'fixeria/mncc'.
calls can be established, but GAPK is never initialized and again, I never see voice data appearing as an MNCC message.
Please check out the configuration examples [1] for mobile app. There you should find the new 'audio' section, where:
io-target hardware
means that audio I/O (by default) should be handled by the hardware (i.e. by Calypso phone). GAPK is not enabled by default.
In order to use GAPK based back-end, use 'gapk':
io-target gapk
It probably makes sense to rename 'gapk' to 'alsa', because at the moment 'gapk' enables both voice playback and capture using the audio system of the host that running mobile.
I never seem to receive a GSM_TCHF_FRAME-message on the MNCC socket.
This can also be configured:
io-target socket
In this case GAPK is not used, and all TCH frames are being forwarded to the MNCC handler 'as-is'.
See [2] commit description for details.
Please also note that audio I/O target != MNCC handler, that actually implements the Call Control logic. See [3] for details.
[1] https://git.osmocom.org/osmocom-bb/tree/doc/examples/mobile/default.cfg?h=fi... [2] https://git.osmocom.org/osmocom-bb/commit/?h=fixeria/audio&id=bdb2854503... [3] https://git.osmocom.org/osmocom-bb/commit/?h=fixeria/audio&id=22edbf3f84...
With best regards, Vadim Yanitskiy.