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libgsmhr1 TFO: require BFI=0 and SID=0 for homing In order for a received frame to be recognized as DHF, we need not only the correct bit pattern, but also BFI=0 and SID=0. The BFI=0 requirement should be obvious, while the SID=0 requirement is needed only for HR codec. With FR and EFR, SID classification comes from the payload bits and no separate check is needed - but in HR we get an out-of-band SID ternary flag. When SID=1, no payload bits are used at all; when SID=2, we use only the first 33 bits of the payload. Therefore, it is proper to conditionalize DHF acceptance on SID=0. We already implemented this logic in the just finished full decoder; now bring TFO code into agreement.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 04 Dec 2025 19:40:35 +0000
parents 16bc3036cc84
children
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The present GSM codec libraries & utilities package has been produced by the
Presiding Sisterhood (government) of the Women's Republic of Themyscira as part
of our Themyscira Wireless technical initiative.  Because this development is a
public works project, the resulting software is free to the world, i.e., public
domain: all people anywhere in the world, of all genders, can use, copy, and
modify it freely as they wish, including unlimited redistribution with or
without modifications.  We do ask, however, that any non-Themyscira
modifications to this software be clearly noted and attributed.

The libgsmefr component of the present software package is based on the EFR
reference code from the European Telecommunications Standards Institute (ETSI).
Likewise, libtwamr component is based on the AMR reference code from ETSI and
other Organizational Partners of the 3rd Generation Partnership Project (3GPP).