view amrefr/tseq-dec.c @ 581:e2d5cad04cbf

libgsmhr1 RxFE: store CN R0+LPC separately from speech In the original GSM 06.06 code the ECU for speech mode is entirely separate from the CN generator, maintaining separate state. (The main intertie between them is the speech vs CN state variable, distinguishing between speech and CN BFIs, in addition to the CN-specific function of distinguishing between initial and update SIDs.) In the present RxFE implementation I initially thought that we could use the same saved_frame buffer for both ECU and CN, overwriting just the first 4 params (R0 and LPC) when a valid SID comes in. However, I now realize it was a bad idea: the original code has a corner case (long sequence of speech-mode BFIs to put the ECU in state 6, then SID and CN-mode BFIs, then a good speech frame) that would be broken by that buffer reuse approach. We could eliminate this corner case by resetting the ECU state when passing through a CN insertion period, but doing so would needlessly increase the behavioral diffs between GSM 06.06 and our version. Solution: use a separate CN-specific buffer for CN R0+LPC parameters, and match the behavior of GSM 06.06 code in this regard.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 13 Feb 2025 10:02:45 +0000
parents 3eadaef8b28f
children
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/*
 * amrefr-tseq-dec is a test program for our libtwamr-based "alternative EFR"
 * decoder: it functions just like gsmefr-etsi-dec, but uses libtwamr as
 * the decoder engine instead of libgsmefr.  Libgsmefr functions are still
 * used for frame unpacking, but not for actual decoding.  Note that there is
 * no DTX support in this version, and the *.dec test sequence being decoded
 * must have SID=0 in every frame.  As a simplification, we also require BFI=0:
 * while it is possible to feed BFI=1 frames to libtwamr decoder (convert to
 * RX_SPEECH_BAD), such support is not needed for decoding the test sequences
 * in amr122_efr.zip, hence we've omitted it for simplicity.
 *
 * The byte order is LE by default or BE with -b option.
 */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include "../libgsmefr/gsm_efr.h"
#include "../libtwamr/tw_amr.h"
#include "../efrtest/etsi.h"

main(argc, argv)
	char **argv;
{
	int big_endian;
	char *infname, *outfname;
	FILE *inf, *outf;
	struct amr_decoder_state *state;
	unsigned frame_no;
	uint8_t input_bits[ETSI_DEC_NWORDS], efr_frame[EFR_RTP_FRAME_LEN];
	struct amr_param_frame amr_frame;
	int16_t pcm[160];
	int rc;

	if (argc == 3 && argv[1][0] != '-') {
		big_endian = 0;
		infname = argv[1];
		outfname = argv[2];
	} else if (argc == 4 && !strcmp(argv[1], "-b")) {
		big_endian = 1;
		infname = argv[2];
		outfname = argv[3];
	} else {
		fprintf(stderr, "usage: %s [-b] input.dec output.out\n",
			argv[0]);
		exit(1);
	}
	inf = fopen(infname, "r");
	if (!inf) {
		perror(infname);
		exit(1);
	}
	outf = fopen(outfname, "w");
	if (!outf) {
		perror(outfname);
		exit(1);
	}
	state = amr_decoder_create();
	if (!state) {
		perror("amr_decoder_create()");
		exit(1);
	}
	amr_frame.type = RX_SPEECH_GOOD;
	amr_frame.mode = 0x87;
	for (frame_no = 0; ; frame_no++) {
		rc = read_etsi_bits(inf, big_endian, input_bits,
				    ETSI_DEC_NWORDS, infname);
		if (!rc)
			break;
		if (input_bits[0]) {
			fprintf(stderr,
			"error in %s frame #%u: BFI != 0 not supported\n",
				infname, frame_no);
			exit(1);
		}
		bits2frame(input_bits + 1, efr_frame, infname, frame_no);
		if (input_bits[245]) {
			fprintf(stderr,
			"error in %s frame #%u: SID != 0 not supported\n",
				infname, frame_no);
			exit(1);
		}
		EFR_frame2params(efr_frame, amr_frame.param);
		amr_decode_frame(state, &amr_frame, pcm);
		if (big_endian)
			write_pcm_be(outf, pcm);
		else
			write_pcm_le(outf, pcm);
	}
	fclose(outf);
	exit(0);
}