--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/trau-decode/extr-main.c	Fri May 24 19:44:14 2024 +0000
@@ -0,0 +1,166 @@
+/*
+ * This program reads a 64 kbit/s timeslot recording file with a focus
+ * on a single sub-timeslot just like trau-parse, but it needs to be
+ * invoked with a starting and ending offset for the frame-aligned
+ * portion of interest (found with trau-parse), and it saves (converts)
+ * the selected stream of TRAU-UL frames to a Themyscira gsmx file.
+ */
+
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+static void
+reduce_to_subslot(buf, right_shift)
+	uint8_t *buf;
+{
+	unsigned n;
+
+	for (n = 0; n < 160; n++) {
+		buf[n] >>= right_shift;
+		buf[n] &= 3;
+	}
+}
+
+static void
+unpack_dibits(dibits, frame_bits)
+	uint8_t *dibits, *frame_bits;
+{
+	int i, inb;
+	uint8_t *op;
+
+	op = frame_bits;
+	for (i = 0; i < 160; i++) {
+		inb = dibits[i];
+		if (inb & 2)
+			*op++ = 1;
+		else
+			*op++ = 0;
+		if (inb & 1)
+			*op++ = 1;
+		else
+			*op++ = 0;
+	}
+}
+
+static unsigned
+bits_to_num(bits, nbits)
+	uint8_t *bits;
+	unsigned nbits;
+{
+	unsigned accum;
+	unsigned n;
+
+	accum = 0;
+	for (n = 0; n < nbits; n++) {
+		accum <<= 1;
+		if (*bits)
+			accum |= 1;
+		bits++;
+	}
+	return accum;
+}
+
+static void
+collect_d_bits(frame_bits, d_bits)
+	uint8_t *frame_bits, *d_bits;
+{
+	bcopy(frame_bits + 33, d_bits, 15);
+	bcopy(frame_bits + 49, d_bits + 15, 15);
+	bcopy(frame_bits + 65, d_bits + 30, 15);
+	bcopy(frame_bits + 81, d_bits + 45, 15);
+	bcopy(frame_bits + 97, d_bits + 60, 15);
+	bcopy(frame_bits + 113, d_bits + 75, 15);
+	bcopy(frame_bits + 129, d_bits + 90, 15);
+	bcopy(frame_bits + 145, d_bits + 105, 15);
+	bcopy(frame_bits + 161, d_bits + 120, 15);
+	bcopy(frame_bits + 177, d_bits + 135, 15);
+	bcopy(frame_bits + 193, d_bits + 150, 15);
+	bcopy(frame_bits + 209, d_bits + 165, 15);
+	bcopy(frame_bits + 225, d_bits + 180, 15);
+	bcopy(frame_bits + 241, d_bits + 195, 15);
+	bcopy(frame_bits + 257, d_bits + 210, 15);
+	bcopy(frame_bits + 273, d_bits + 225, 15);
+	bcopy(frame_bits + 289, d_bits + 240, 15);
+	bcopy(frame_bits + 305, d_bits + 255, 5);
+}
+
+static void
+process_frame(cur_offset, dibits, outf)
+	u_long cur_offset;
+	uint8_t *dibits;
+	FILE *outf;
+{
+	uint8_t frame_bits[320], d_bits[260];
+	unsigned c1_5;
+
+	unpack_dibits(dibits, frame_bits);
+	if (frame_bits[28]) {			/* C12 aka BFI */
+		putc(0xBF, outf);
+		putc(frame_bits[31], outf);	/* C15 aka TAF */
+		return;
+	}
+	collect_d_bits(frame_bits, d_bits);
+	c1_5 = bits_to_num(frame_bits + 17, 5);
+	switch (c1_5) {
+	case 0x02:
+		convert_fr_frame(d_bits, outf);
+		break;
+	case 0x1A:
+		convert_efr_frame(d_bits, outf);
+		break;
+	default:
+		fprintf(stderr,
+			"error: unknown frame type 0x%x at file offset 0x%lx\n",
+			c1_5, cur_offset);
+		exit(1);
+	}
+}
+
+main(argc, argv)
+	char **argv;
+{
+	FILE *inf, *outf;
+	int subslot, right_shift;
+	u_long start_offset, end_offset, cur_offset;
+	uint8_t readbuf[160];
+	int cc;
+
+	if (argc != 6) {
+		fprintf(stderr, "usage: %s binfile subslot start end outfile\n",
+			argv[0]);
+		exit(1);
+	}
+	inf = fopen(argv[1], "r");
+	if (!inf) {
+		perror(argv[1]);
+		exit(1);
+	}
+	subslot = atoi(argv[2]);
+	if (subslot < 0 || subslot > 3) {
+		fprintf(stderr, "error: invalid subslot argument\n");
+		exit(1);
+	}
+	right_shift = (3 - subslot) * 2;
+	start_offset = strtoul(argv[3], 0, 0);
+	fseek(inf, start_offset, SEEK_SET);
+	end_offset = strtoul(argv[4], 0, 0);
+	outf = fopen(argv[5], "w");
+	if (!outf) {
+		perror(argv[5]);
+		exit(1);
+	}
+	for (cur_offset = start_offset; ; cur_offset += 160) {
+		if (end_offset && cur_offset >= end_offset)
+			break;
+		cc = fread(readbuf, 1, 160, inf);
+		if (cc < 160)
+			break;
+		reduce_to_subslot(readbuf, right_shift);
+		process_frame(cur_offset, readbuf, outf);
+	}
+	exit(0);
+}