From andreas at galauner.de Tue Nov 20 09:56:43 2018 From: andreas at galauner.de (Andreas Galauner) Date: Tue, 20 Nov 2018 10:56:43 +0100 Subject: Voice calls over Virtual Um Message-ID: <06f10b74-234d-5234-5492-67061d47b83a@galauner.de> Hi, 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. I looked around and found a repository [1] with an MNCC example application which sends voice samples. Calls are established and can be picked up, but on the other end, but I never seem to receive a GSM_TCHF_FRAME-message on the MNCC socket. I then checked out the fixeria/mncc branch [2] which includes GAPK integration which can use ALSA devices for audio, because that's what I need anyway at some point for my project I'm working on. Again, calls can be established, but GAPK is never initialized and again, I never see voice data appearing as an MNCC message. The GAPK audio backend is supposed to be initialized [3] when a CHANNEL MODE MODIFY message is received from the network. I never see the network request a channel mode modify though. I don't know enough about GSM to find out if that message is always supposed to be sent when a call is established or not. Did anybody ever transport audio with two OsmocomBB instances over the Virtual Um interface? Thanks, - Andy [1]: https://github.com/GerardPinto/call-control-mncc-sap [2]: https://git.osmocom.org/osmocom-bb/log/?h=fixeria/mncc [3]: https://git.osmocom.org/osmocom-bb/tree/src/host/layer23/src/mobile/gsm48_rr.c?h=fixeria/mncc&id=c7f6b1c53426c1d57221eaa7ce371ba5e42f507e#n3444 From axilirator at gmail.com Tue Nov 27 15:05:39 2018 From: axilirator at gmail.com (Vadim Yanitskiy) Date: Tue, 27 Nov 2018 22:05:39 +0700 Subject: Voice calls over Virtual Um Message-ID: 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=fixeria/audio [2] https://git.osmocom.org/osmocom-bb/commit/?h=fixeria/audio&id=bdb2854503afde3ee215f24b1b17b4d12e1c3c44 [3] https://git.osmocom.org/osmocom-bb/commit/?h=fixeria/audio&id=22edbf3f846b13a404dd4e49c3ed25d757d3f527 With best regards, Vadim Yanitskiy.