Each of the 3 tfo-*.bin files in this directory is an extract from an MSC-side
E1 timeslot recording in a Nokia TCSM2 TFO session involving a cross-connect
between two TRAU channels.  The extracts have been chosen to begin at the point
where the TRAU starts emitting TFO frames, thereby beginning with a series of
TFO frames that contain an embedded TFO_TRANS message.  In each experiment, one
of the two cross-connected TRAU channels emitted two "plain" TFO frames (not
containing embedded TFO messages) in between the initial embedded TFO_TRANS and
the subsequent embedded TFO_REQ_L; this channel was chosen for the present
extracts.  Each extract is thus 2560 PCM samples, containing 16 aligned TFO
frames: 5 carrying TFO_TRANS, 2 plain, 9 carrying TFO_REQ_L.

In each of the three TCSM2 sessions from which these TFO frame extracts were
taken, the Ater UL input was fed with a stream of good DHFs (decoder homing
frames) for the respective codec, hence the TFO frame content is nothing but
these DHFs.  In the case of FR and EFR captures, one of the 16 consecutive
frames also exhibits TAF=1.  OTOH, the same does not hold for HR: the TRAU-8k
frame format used in TFO and in most Abis implementations carries TAF only for
BFIs and invalid SID, but not for good speech or valid SID frames.

The tfo-*.hex files that are generated from tfo-*.bin by the Makefile in this
directory are intended to serve as unit tests for TFO frame extraction functions
that are currently being implemented in libosmotrau.  The lack of frame content
diversity (nothing but DHF) is not seen as a problem: the objective here is to
test TFO frame extraction functions; the higher-level logic of TRAU frame
decoding has its own unit tests.