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changeset 536:a3300483ae74

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doc/FR1-library-API: document return value from gsmfr_tfo_xfrm_*
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 21 Sep 2024 20:48:58 +0000
parents bf7bbc7d494f
children f9eefb61fb2f
files doc/FR1-library-API
diffstat 1 files changed, 9 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/doc/FR1-library-API	Fri Sep 20 07:27:18 2024 +0000
+++ b/doc/FR1-library-API	Sat Sep 21 20:48:58 2024 +0000
@@ -374,11 +374,20 @@
 and the TFO transform is that the former emits linear PCM output, whereas the
 latter emits 33-byte GSM-FR codec frames to be sent to call leg B downlink.
 
+The return value from gsmfr_tfo_xfrm_main() is the same as that of
+gsmfr_fulldec_rtp_in(): 0 if the the RTP input was considered good or -1 if it
+is invalid.  In the case of invalid RTP input that produces -1 return value,
+gsmfr_tfo_xfrm_main() calls gsmfr_preproc_bfi(), just like how
+gsmfr_fulldec_rtp_in() calls gsmfr_fulldec_bfi() under the same conditions.
+
 If DTXd is in use, then the call to gsmfr_tfo_xfrm_main() needs to be directly
 followed by a call to gsmfr_tfo_xfrm_dtxd(), operating on the same output buffer
 with the same state structure.  The output will then be changed to SID when
 appropriate for the current state.
 
+The return value from gsmfr_tfo_xfrm_dtxd() is the SP flag of GSM 06.31: 1 if
+the output frame is speech or 0 if it is SID.
+
 TFO transform homing
 --------------------