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+++ b/tfo-ut/README	Wed Mar 19 01:39:57 2025 +0000
@@ -0,0 +1,25 @@
+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.