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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
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535:bf7bbc7d494f 536:a3300483ae74
372 RTP wrapper is convenient for the same reasons as in the case of the full 372 RTP wrapper is convenient for the same reasons as in the case of the full
373 decoder. In this mode of usage, the only difference between the full decoder 373 decoder. In this mode of usage, the only difference between the full decoder
374 and the TFO transform is that the former emits linear PCM output, whereas the 374 and the TFO transform is that the former emits linear PCM output, whereas the
375 latter emits 33-byte GSM-FR codec frames to be sent to call leg B downlink. 375 latter emits 33-byte GSM-FR codec frames to be sent to call leg B downlink.
376 376
377 The return value from gsmfr_tfo_xfrm_main() is the same as that of
378 gsmfr_fulldec_rtp_in(): 0 if the the RTP input was considered good or -1 if it
379 is invalid. In the case of invalid RTP input that produces -1 return value,
380 gsmfr_tfo_xfrm_main() calls gsmfr_preproc_bfi(), just like how
381 gsmfr_fulldec_rtp_in() calls gsmfr_fulldec_bfi() under the same conditions.
382
377 If DTXd is in use, then the call to gsmfr_tfo_xfrm_main() needs to be directly 383 If DTXd is in use, then the call to gsmfr_tfo_xfrm_main() needs to be directly
378 followed by a call to gsmfr_tfo_xfrm_dtxd(), operating on the same output buffer 384 followed by a call to gsmfr_tfo_xfrm_dtxd(), operating on the same output buffer
379 with the same state structure. The output will then be changed to SID when 385 with the same state structure. The output will then be changed to SID when
380 appropriate for the current state. 386 appropriate for the current state.
387
388 The return value from gsmfr_tfo_xfrm_dtxd() is the SP flag of GSM 06.31: 1 if
389 the output frame is speech or 0 if it is SID.
381 390
382 TFO transform homing 391 TFO transform homing
383 -------------------- 392 --------------------
384 393
385 3GPP specs are silent on whether or not TFO transforms should implement homing, 394 3GPP specs are silent on whether or not TFO transforms should implement homing,