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Harald Welte laforge at osmocom.orgHi Philipp (and lurkers on this list),
I've just pushed an update to the @laforge/trau@ branch of libosmo-abis,
which contains the new code modules for E1 / TRAU usage, and also a small
test program and test data.
The test program takes a raw binary dump created from an E1 timeslot with
TRAU frames captured of a BS-11 and converts that to RTP packets. You can feed
those RTP packets into osmo-gapk to play them back. The audio is clear, there
are just a few seconds of quiet at the beginning before anything is audible.
The patches also add an "I460" mode to e1_input. So from the osmo-mgw side,
I think we need to
* link against libosmo-abis and call e1inp_init + e1inp_vty_init()
* use existing VTY code to configure E1 line numbers / drivers / ports
* call e1inp_ts_config_i460() on every timeslot we want to use (this should *not*
happen on all timeslots, as some of them are used for signalling by the BSC)
* call osmo_i460_subchan_add() / osmo_i460_subchan_del() for each i.460 sub-slot
we want to use
* build the processing chain like in libosmo-abis/contrib/trau2rtp/trau2rtp.c
via i460 -> trau_sync -> osmo_trau_frame_decode_16k/osmo_trau_frame_decode_8k -> osmo_trau2rtp
I believe this should be at a stage where it can be integrated into osmo-mgw. The API
may not be 100% stable yet, but it shouldn't change completely. The main missing
bits are:
* allow selection of sync pattern in trau_sync.c (or auto-detect?)
* handling of T-bits for alignment of air-interface timing with downlink
TRAU frame timing
I will next be hacking on a small tool that will speak the 'osmo-e1d' protocol
but use binary capture files that are looped over and over again. This way
you should be able to use libosmo-abis e1_input without any physical card and
still get TRAU frame data.
At a lower priority, I'd like to look into support for HRv1 and AMR TRAU
frames on 16k sub-slots.
--
- Harald Welte <laforge at osmocom.org> http://laforge.gnumonks.org/
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