add (untested) TRAU frame decoder with support for FR/EFR and AMR

1 files changed, 115 insertions, 0 deletions

diff --git a/src/trau_frame.c b/src/trau_frame.c
new file mode 100644
index 000000000..e0238ce02
--- /dev/null
+++ b/src/trau_frame.c
@@ -0,0 +1,115 @@
+/* TRAU frame handling according to GSM TS 08.60 */
+
+/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+
+#include <openbsc/trau_frame.h>
+
+static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num)
+{
+	int i;
+	u_int32_t ret = 0;
+
+	for (i = offset; i < offset + num; i++) {
+		ret = ret << 1;
+		if (bitbuf[i])
+			ret |= 1;
+	}
+	return ret;
+}
+
+/* Decode according to 3.1.1 */
+static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
+{
+	int i;
+	int d_idx = 0;
+
+	/* C1 .. C15 */
+	memcpy(fr->c_bits+0, trau_bits+17, 15);
+	/* C16 .. C21 */
+	memcpy(fr->c_bits+15, trau_bits+310, 6);
+	/* T1 .. T4 */
+	memcpy(fr->t_bits+0, trau_bits+316, 4);
+	/* D1 .. D255 */
+	for (i = 32; i < 304; i+= 16) {
+		memcpy(fr->d_bits + d_idx, trau_bits+i+1, 15);
+		d_idx += 15;
+	}
+	/* D256 .. D260 */
+	memcpy(fr->d_bits + d_idx, trau_bits + 305, 5);
+}
+
+static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
+{
+	int i;
+	int d_idx = 0;
+
+	/* C1 .. C15 */
+	memcpy(fr->c_bits+0, trau_bits+17, 15);
+	/* C16 .. C25 */
+	memcpy(fr->c_bits+15, trau_bits+33, 10);
+	/* T1 .. T4 */
+	memcpy(fr->t_bits+0, trau_bits+316, 4);
+	/* D1 .. D5 */
+	memcpy(fr->d_bits, trau_bits+43, 5);
+	/* D6 .. D245 */
+	for (i = 48; i < 304; i += 16) {
+		memcpy(fr->d_bits + d_idx, trau_bits+i+1, 15);
+		d_idx += 15;
+	}
+	/* D246 .. D256 */
+	memcpy(fr->d_bits + d_idx, trau_bits + 305, 11);
+}
+
+int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits)
+{
+	u_int8_t cbits5 = get_bits(trau_bits, 17, 5);
+
+	switch (cbits5) {
+	case TRAU_FT_FR_UP:
+	case TRAU_FT_FR_DOWN:
+	case TRAU_FT_EFR:
+		decode_fr(fr, trau_bits);
+		break;
+	case TRAU_FT_AMR:
+		decode_amr(fr, trau_bits);
+		break;
+	case TRAU_FT_OM_UP:
+	case TRAU_FT_OM_DOWN:
+	case TRAU_FT_DATA_UP:
+	case TRAU_FT_DATA_DOWN:
+	case TRAU_FT_D145_SYNC:
+	case TRAU_FT_EDATA:
+		fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
+		return -1;
+		break;
+	default:
+		fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5);
+		return -1;
+		break;
+	}
+
+	return 0;
+}