view hrutil/read-cod.c @ 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 bb36ef735f25
children
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/*
 * In this module we implement the utility function for reading ETSI
 * GSM-HR *.cod files in either LE or BE format.
 */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include "../libgsmhr1/tw_gsmhr.h"

read_cod_frame(inf, big_endian, params, filename_for_errs, frame_no)
	FILE *inf;
	int16_t *params;
	char *filename_for_errs;
	unsigned frame_no;
{
	uint8_t file_bytes[GSMHR_NUM_PARAMS_ENC * 2], *sp;
	int cc;
	unsigned n;
	uint16_t val;

	cc = fread(file_bytes, 2, GSMHR_NUM_PARAMS_ENC, inf);
	if (cc == 0)
		return 0;
	if (cc != GSMHR_NUM_PARAMS_ENC) {
		fprintf(stderr, "error: short read from %s\n",
			filename_for_errs);
		exit(1);
	}
	sp = file_bytes;
	for (n = 0; n < GSMHR_NUM_PARAMS_ENC; n++) {
		if (big_endian)
			val = ((uint16_t) sp[0] << 8) | ((uint16_t) sp[1]);
		else
			val = ((uint16_t) sp[1] << 8) | ((uint16_t) sp[0]);
		params[n] = val;
		sp += 2;
	}
	if (gsmhr_check_encoder_params(params) < 0) {
		fprintf(stderr,
			"error in %s frame #%u: wrong format or wrong endian\n",
			filename_for_errs, frame_no);
		exit(1);
	}
	return 1;
}