--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/trau-decode/amr8-common.c	Thu Nov 20 16:52:21 2025 +0000
@@ -0,0 +1,214 @@
+/*
+ * Here we implement parsing/decoding of TRAU-AMR-8k frames per 3GPP TS 48.061,
+ * striving to decode and display as much as we can.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include "osmo_bits.h"
+
+/*
+ * AMR TRAU parity (same as EFR)
+ *
+ * g(x) = x^3 + x^1 + 1
+ */
+static const struct osmo_crc8gen_code gsm0860_amr_crc3 = {
+	.bits = 3,
+	.poly = 0x3,
+	.init = 0x0,
+	.remainder = 0x7,
+};
+
+static int saved_mode, saved_mode_valid;
+
+static char *fclass_names[4] = {
+	"No_Speech", "Speech_Bad", "Speech_Degraded", "Speech_Good"
+};
+
+static char *nospch_class_names[8] = {
+	"No_Data", "invalid", "invalid", "invalid",
+	"Sid_Bad", "Sid_Update", "Onset", "Sid_First"
+};
+
+static const uint8_t params_lsf_475_515[] = {8, 8, 7, 0};
+static const uint8_t params_lsf_59_67_74[] = {8, 9, 9, 0};
+
+static const uint8_t params_475_sf1[]  = {8, 7, 2, 8, 0};
+static const uint8_t params_475_sf3[]  = {4, 7, 2, 8, 0};
+static const uint8_t params_475_sf24[] = {4, 7, 2, 0};
+
+static const uint8_t params_515_sf1[]   = {8, 7, 2, 6, 0};
+static const uint8_t params_515_sf234[] = {4, 7, 2, 6, 0};
+
+static const uint8_t params_59_sf13[] = {8, 9, 2, 6, 0};
+static const uint8_t params_59_sf24[] = {4, 9, 2, 6, 0};
+
+static const uint8_t params_67_sf13[] = {8, 11, 3, 7, 0};
+static const uint8_t params_67_sf24[] = {4, 11, 3, 7, 0};
+
+static const uint8_t params_74_sf13[] = {8, 13, 4, 7, 0};
+static const uint8_t params_74_sf24[] = {5, 13, 4, 7, 0};
+
+static const uint8_t params_sid[] = {3, 8, 9, 9, 6, 0};
+
+static const ubit_t bit8_0[8] = { 0, };
+
+/*!< check sync pattern for AMR No_Speech + low bit rate */
+static bool is_amr_low(const ubit_t *bits)
+{
+	int i;
+
+	/* TS 08.61 Section 6.8.2.1.2 */
+	if (memcmp(bits, bit8_0, sizeof(bit8_0)))
+		return false;
+	if (bits[8] != 1)
+		return false;
+	if (bits[16] != 1)
+		return false;
+	if (bits[24] != 0 || bits[25] != 1)
+		return false;
+	for (i = 32; i < 20 * 8; i += 8) {
+		if (bits[i] != 1)
+			return false;
+	}
+	return true;
+}
+
+/*!< check sync pattern for AMR 6.7kBit/s */
+static bool is_amr_67(const ubit_t *bits)
+{
+	int i;
+
+	/* TS 08.61 Section 6.8.2.1.3 */
+	if (memcmp(bits, bit8_0, sizeof(bit8_0)))
+		return false;
+	if (bits[8] != 1)
+		return false;
+	if (bits[16] != 1)
+		return false;
+	if (bits[24] != 1)
+		return false;
+	if (bits[32] != 1)
+		return false;
+	if (bits[40] != 0)
+		return false;
+	for (i = 48; i < 20 * 8; i += 16) {
+		if (bits[i] != 1)
+			return false;
+	}
+	return true;
+}
+
+/*!< check sync pattern for AMR 7.4kBit/s */
+static bool is_amr_74(const ubit_t *bits)
+{
+	if (bits[0] != 0 || bits[1] != 0 || bits[2] != 1)
+		return false;
+	if (bits[8] != 0)
+		return false;
+	if (bits[16] != 1)
+		return false;
+	if (bits[24] != 0)
+		return false;
+
+	return true;
+}
+
+static unsigned
+bits_to_num(bits, nbits)
+	ubit_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
+print_generic_params(bits, ltab)
+	ubit_t *bits;
+	uint8_t *ltab;
+{
+	uint8_t *tp;
+	unsigned n, p;
+
+	for (tp = ltab; n = *tp; tp++) {
+		p = bits_to_num(bits, n);
+		bits += n;
+		printf(" %u", p);
+	}
+}
+
+static void
+print_speech_params(bits, ltab)
+	ubit_t *bits;
+	uint8_t *ltab;
+{
+	fputs("   ", stdout);
+	print_generic_params(bits, ltab);
+	putchar('\n');
+}
+
+static void
+check_spare_bits(bits, nbits, desc)
+	ubit_t *bits;
+	unsigned nbits;
+	char *desc;
+{
+	while (nbits) {
+		if (*bits == 0)
+			break;
+		bits++;
+		nbits--;
+	}
+	if (!nbits)
+		return;
+	printf("    Extra data in bits %s\n", desc);
+}
+
+static void
+handle_amr8_low(frame_bits)
+	ubit_t *frame_bits;
+{
+	puts("  TRAU-AMR-8k Low format, decoding to be implemented");
+}
+
+static void
+handle_amr8_6k7(frame_bits)
+	ubit_t *frame_bits;
+{
+	puts("  TRAU-AMR-8k MR67 format, decoding to be implemented");
+}
+
+static void
+handle_amr8_7k4(frame_bits)
+	ubit_t *frame_bits;
+{
+	puts("  TRAU-AMR-8k MR74 format, decoding to be implemented");
+}
+
+void
+print_amr8_frame(frame_bits)
+	ubit_t *frame_bits;
+{
+	if (is_amr_low(frame_bits))
+		handle_amr8_low(frame_bits);
+	else if (is_amr_67(frame_bits))
+		handle_amr8_6k7(frame_bits);
+	else if (is_amr_74(frame_bits))
+		handle_amr8_7k4(frame_bits);
+	else
+		puts("  Unrecognized format by sync pattern");
+}