--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/trau-decode/trau-sync8.c	Sun Aug 18 06:26:23 2024 +0000
@@ -0,0 +1,150 @@
+/*
+ * This program reads a 64 kbit/s timeslot recording file, examines one
+ * of the eight 8 kbit/s subslots (selected), looks for the sync pattern of
+ * GSM 08.61 (HRv1 speech or HR data), and dumps each synced frame
+ * as a hex line.
+ */
+
+#include <sys/types.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
+
+static uint8_t *filebuf;
+static unsigned total_size;
+
+static void
+read_ts_file(filename, subslot_arg)
+	char *filename, *subslot_arg;
+{
+	FILE *inf;
+	struct stat st;
+	int subslot, right_shift;
+	unsigned n;
+	uint8_t *dp;
+	int b;
+
+	inf = fopen(filename, "r");
+	if (!inf) {
+		perror(filename);
+		exit(1);
+	}
+	fstat(fileno(inf), &st);
+	if (!S_ISREG(st.st_mode)) {
+		fprintf(stderr, "error: %s is not a regular file\n", filename);
+		exit(1);
+	}
+	total_size = st.st_size;
+	if (total_size < 160) {
+		fprintf(stderr, "error: %s is too short\n", filename);
+		exit(1);
+	}
+	filebuf = malloc(total_size);
+	if (!filebuf) {
+		perror("malloc of file size");
+		exit(1);
+	}
+	subslot = atoi(subslot_arg);
+	if (subslot < 0 || subslot > 7) {
+		fprintf(stderr, "error: invalid subslot argument\n");
+		exit(1);
+	}
+	right_shift = 7 - subslot;
+	dp = filebuf;
+	for (n = 0; n < total_size; n++) {
+		b = getc(inf);
+		if (b < 0) {
+			fprintf(stderr,
+			"error: getc() returned EOF contrary to st_size\n");
+			exit(1);
+		}
+		*dp++ = (b >> right_shift) & 1;
+	}
+	fclose(inf);
+}
+
+static int
+check_sync(pos)
+	unsigned pos;
+{
+	uint8_t *cand = filebuf + pos;
+	unsigned n;
+
+	for (n = 0; n < 8; n++) {
+		if (cand[n])
+			return 0;
+	}
+	if (!cand[8])
+		return 0;
+	if (cand[16])
+		return 0;
+	if (!cand[17])
+		return 0;
+	for (n = 3; n < 20; n++) {
+		if (!cand[n * 8])
+			return 0;
+	}
+	return 1;
+}
+
+static void
+process_frame(pos)
+	unsigned pos;
+{
+	uint8_t *sp = filebuf + pos;
+	unsigned n, m, d;
+
+	for (n = 0; n < 40; n++) {
+		d = 0;
+		for (m = 0; m < 4; m++) {
+			d <<= 1;
+			d |= *sp++;
+		}
+		printf("%x", d);
+	}
+	putchar('\n');
+}
+
+static void
+process_filebuf()
+{
+	unsigned p, endp;
+	int sync = 0, match;
+
+	endp = total_size - 160;
+	for (p = 0; p < endp; ) {
+		match = check_sync(p);
+		if (match != sync) {
+			printf("# %s frame sync at file offset 0x%x\n",
+				match ? "Acquired" : "Lost", p);
+		}
+		if (match) {
+			process_frame(p);
+			if (!filebuf[p+158] && !filebuf[p+159]) {
+				printf(
+			  "# both T bits equal 0, shifting frame alignment\n");
+				p += 158;
+			} else
+				p += 160;
+		} else
+			p++;
+		sync = match;
+	}
+}
+
+main(argc, argv)
+	char **argv;
+{
+	if (argc != 3) {
+		fprintf(stderr, "usage: %s binfile subslot\n", argv[0]);
+		exit(1);
+	}
+	read_ts_file(argv[1], argv[2]);
+	process_filebuf();
+	exit(0);
+}