GAPK status update

Dear Osmocom community, I have been working on GAPK (GSM Audio Packet Knife) for some time, and now I would like to share some achievements. Previously GAPK was represented as a single binary that could be called with some command line arguments in order to perform required operations. This is only handy for humans, but not for other programs, which may also need to perform some format / codec conversations or audio capture / playback. One of such programs is the mobile from OsmocomBB project. Currently, when you're making a voice call, both audio capture and playback are only possible on the L1 side, i.e. on a Calypso based phone. Of course, the audio stream can be redirected via MNCC socket, but this is not what a regular OsmocomBB user would like to do. Moreover, there is a lack of AMR codec support. Also, there is another GNURadio based project named GR-GSM. In short, this is a set of blocks for GSM signal reception, demodulation and further processing. At the moment, one has TCH Full Rate decoding capabilities only. Audio playback is not supported yet. Having these projects in my mind, I have got an idea of creating a shared library from the GAPK source code. And, a few days ago I was managed to get the audio playback working in OsmocomBB. I hope, this library will be also usable for other projects. Brief list of changes were made: - Composed a shared library named libosmogapk - All exposed symbols have got an 'osmo_gapk' prefix - Added a pkg-config manifest and a symbol export map - Integrated the Osmocom logging framework - Benchmarking is now disabled by default - Processing queue now based on the linuxlist - Fixed program exit due to ALSA buffer underrun - Fixed ALSA audio playback from file - Old gapk application was renamed to 'osmo-gapk' and linked against the library - Adjusted verbosity level (normal / debug) - Fixed I/O combinations (ALSA, RTP, file...) check All changes could be found at the fixeria/lib branch of GAPK. I hope to see them merged, and open for discussions ;) With best regards, Vadim Yanitskiy.