--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hrutil/decode.c	Fri Dec 05 02:43:19 2025 +0000
@@ -0,0 +1,70 @@
+/*
+ * This file is the main module for gsmhr-decode utility.  This utility
+ * is intended to serve as the "user-friendly" decoder for GSM-HR encoded
+ * speech, reading TW-TS-005 Annex B as input and emitting playable WAV
+ * as output.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "../libgsmhr1/tw_gsmhr.h"
+#include "../libtest/tw5reader.h"
+#include "../libtest/wavwriter.h"
+#include "../libtest/pcmwrite.h"
+
+main(argc, argv)
+	char **argv;
+{
+	FILE *hexf;
+	void *wav;
+	unsigned lineno;
+	struct gsmhr_decoder_state *state;
+	uint8_t frame[TWTS005_MAX_FRAME];
+	unsigned frame_len;
+	int16_t params[GSMHR_NUM_PARAMS_DEC];
+	int16_t pcm[160];
+	int rc;
+
+	if (argc != 3) {
+		fprintf(stderr, "usage: %s input.hex output.wav\n", argv[0]);
+		exit(1);
+	}
+	hexf = fopen(argv[1], "r");
+	if (!hexf) {
+		perror(argv[1]);
+		exit(1);
+	}
+	lineno = 0;
+	wav = wav_write_open(argv[2], 8000, 16, 1);
+	if (!wav) {
+		perror(argv[2]);
+		exit(1);
+	}
+	state = gsmhr_decoder_create();
+	if (!state) {
+		fprintf(stderr, "gsmhr_decoder_create() failed!\n");
+		exit(1);
+	}
+	for (;;) {
+		rc = twts005_read_frame(hexf, &lineno, frame, &frame_len);
+		if (rc < 0) {
+			fprintf(stderr, "%s line %u: not valid TW-TS-005\n",
+				argv[1], lineno);
+			exit(1);
+		}
+		if (!rc)
+			break;
+		rc = gsmhr_rtp_in_direct(frame, frame_len, params);
+		if (rc < 0) {
+			fprintf(stderr,
+				"%s line %u: not a valid GSM-HR frame\n",
+				argv[1], lineno);
+			exit(1);
+		}
+		gsmhr_decode_frame(state, params, pcm);
+		write_pcm_to_wav(wav, pcm);
+	}
+	wav_write_close(wav);
+	exit(0);
+}