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annotate libgsmefr/e_homing.h @ 604:54f0f1b74c25

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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 035424a6ca83
children
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1 /**************************************************************************
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2 *
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3 * File Name: e_homing.h
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4 *
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5 * Purpose: Contains the prototypes for all the functions of
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6 * encoder homing.
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7 *
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8 **************************************************************************/
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10 #define EHF_MASK 0x0008 /* Encoder Homing Frame pattern */
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12 /* Function Prototypes */
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14 Word16 encoder_homing_frame_test (const Word16 input_frame[]);
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988fd7ff514f libgsmefr: add state pointers to ETSI function prototypes
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16 void encoder_reset (struct EFR_encoder_state *st);