view efrtest/rec2etsi.c @ 242:f081a6850fb5

libgsmfrp: new refined implementation The previous implementation exhibited the following defects, which are now fixed: 1) The last received valid SID was cached forever for the purpose of handling future invalid SIDs - we could have received some valid SID ages ago, then lots of speech or NO_DATA, and if we then get an invalid SID, we would resurrect the last valid SID from ancient history - a bad design. In our new design, we handle invalid SID based on the current state, much like BFI. 2) GSM 06.11 spec says clearly that after the second lost SID (received BFI=1 && TAF=1 in CN state) we need to gradually decrease the output level, rather than jump directly to emitting silence frames - we previously failed to implement such logic. 3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes in a SID frame. What should we do if we receive an otherwise valid SID frame with different Xmaxc? Our previous approach would replicate this Xmaxc oddity in every subsequent generated CN frame, which is rather bad. In our new design, the very first CN frame (which can be seen as a transformation of the SID frame itself) retains the original 4 distinct Xmaxc, but all subsequent CN frames are based on the Xmaxc from the last subframe of the most recent SID.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 09 May 2023 05:16:31 +0000
parents bd832a456339
children
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/*
 * This program reads in an EFR session recording in our binary format
 * (presumably obtained by converting from an RTP capture on the network
 * side or from a Calypso DSP readout on the mobile side) and converts
 * it into ETSI *.dec format, to be fed to ETSI decoder test program.
 *
 * The output from this program is in the local machine's native byte order.
 */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include "../libgsmefr/gsm_efr.h"
#include "../libtest/binreader.h"

static void
frame2bits(frame, bits)
	uint8_t *frame;
	uint16_t *bits;
{
	unsigned nb, byte, mask, bit;

	for (nb = 0; nb < 31; nb++) {
		byte = *frame++;
		for (mask = 0x80; mask; mask >>= 1) {
			if (byte & mask)
				bit = 1;
			else
				bit = 0;
			*bits++ = bit;
		}
	}
}

main(argc, argv)
	char **argv;
{
	FILE *binf, *outf;
	uint8_t frame[BINFILE_MAX_FRAME];
	uint16_t bits[250];
	int rc;

	if (argc != 3) {
		fprintf(stderr, "usage: %s input.gsmx output.dec\n", argv[0]);
		exit(1);
	}
	binf = fopen(argv[1], "r");
	if (!binf) {
		perror(argv[1]);
		exit(1);
	}
	outf = fopen(argv[2], "w");
	if (!outf) {
		perror(argv[2]);
		exit(1);
	}
	for (;;) {
		rc = binfile_read_frame(binf, frame);
		if (rc < 0) {
			fprintf(stderr, "error: garbage in %s\n", argv[1]);
			exit(1);
		}
		if (!rc)
			break;
		if (frame[0] == 0xBF) {
			bits[3] = 1;			/* BFI */
			bzero(bits + 4, 245 * 2);
			bits[249] = frame[1] & 1;	/* TAF */
		} else if ((frame[0] & 0xF0) == 0xC0) {
			frame2bits(frame, bits);
			bits[248] = EFR_sid_classify(frame);
			bits[249] = 0;			/* TAF */
		} else {
			fprintf(stderr,
				"error: %s is not in EFR codec format\n",
				argv[1]);
			exit(1);
		}
		fwrite(bits + 3, 2, 247, outf);
	}
	fclose(outf);
	exit(0);
}