view efrtest/dlcap-gsmx.c @ 183:452c1d5a6268

libgsmefr BFI w/o data: emit zero output after decoder reset In real-life usage, each EFR decoder session will most likely begin with lots of BFI frames before the first real frame arrives. However, because the spec-defined home state of the decoder is speech rather than CN, our regular logic for BFI w/o data would have to feed pseudorandom noise to the decoder (in the "fixed codebook excitation pulses" part), which is silly to do at the beginning of the decoder session right out of reset. Therefore, let's check reset_flag_old, and if we are still in the reset state, simply emit zero output.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 03 Jan 2023 00:12:18 +0000
parents 6e39fc0134da
children
line wrap: on
line source

/*
 * This program reads a TCH/EFS downlink capture produced with FreeCalypso tools
 * (fw version with TCH downlink sniffing feature and fc-shell tch record)
 * and converts it into our extended-libgsm binary format, to be further
 * fed to gsmefr-decode or other tools.
 */

#include <ctype.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>

main(argc, argv)
	char **argv;
{
	FILE *inf, *outf;
	char linebuf[128];
	int lineno, rc;
	uint16_t status_words[3];
	uint8_t tidsp_bytes[33], efr_bytes[31], bfi[2];
	unsigned fn_mod_104;

	if (argc != 3) {
		fprintf(stderr, "usage: %s infile outfile\n", argv[0]);
		exit(1);
	}
	inf = fopen(argv[1], "r");
	if (!inf) {
		perror(argv[1]);
		exit(1);
	}
	outf = fopen(argv[2], "w");
	if (!outf) {
		perror(argv[2]);
		exit(1);
	}
	for (lineno = 1; fgets(linebuf, sizeof linebuf, inf); lineno++) {
		/* support both old and new formats */
		if (isxdigit(linebuf[0]) && isxdigit(linebuf[1]) &&
		    isxdigit(linebuf[2]) && isxdigit(linebuf[3])) {
			rc = parse_dlcap_common(linebuf, status_words,
						tidsp_bytes);
			if (rc < 0) {
invalid:			fprintf(stderr,
				"error: %s is not in the expected format\n",
					argv[1]);
				exit(1);
			}
			fn_mod_104 = 0;		/* won't have TAF */
		} else if (!strncmp(linebuf, "EFR ", 4)) {
			rc = parse_dlcap_common(linebuf + 4, status_words,
						tidsp_bytes);
			if (rc < 0)
				goto invalid;
			if (linebuf[85] != ' ')
				goto invalid;
			if (!isdigit(linebuf[86]))
				goto invalid;
			fn_mod_104 = strtoul(linebuf + 86, 0, 10);
		} else
			goto invalid;
		/*
		 * DSP flags are documented in the TCH-tap-modes article
		 * in freecalypso-docs.
		 */
		if ((status_words[0] & 0xC204) == 0xC000) {
			efr_tidsp_to_std(tidsp_bytes, efr_bytes);
			fwrite(efr_bytes, 1, 31, outf);
		} else {
			bfi[0] = 0xBF;
			bfi[1] = fn_mod_104 == 60;
			fwrite(bfi, 1, 2, outf);
		}
	}
	exit(0);
}