FreeCalypso > hg > gsm-codec-lib
view LICENSE @ 604:54f0f1b74c25
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).
