l1/tch3: Add support for TCH3 (speech) channel coding

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

2 files changed, 184 insertions, 1 deletions

diff --git a/src/l1/Makefile.am b/src/l1/Makefile.am
index 05e068c..0a03e5f 100644
--- a/src/l1/Makefile.am
+++ b/src/l1/Makefile.am
@@ -6,4 +6,4 @@ noinst_LIBRARIES = libgmr1-l1.a
 
 libgmr1_l1_a_SOURCES = \
 	conv.c crc.c interleave.c punct.c scramb.c \
-	bcch.c ccch.c facch3.c
+	bcch.c ccch.c facch3.c tch3.c
diff --git a/src/l1/tch3.c b/src/l1/tch3.c
new file mode 100644
index 0000000..638819b
--- /dev/null
+++ b/src/l1/tch3.c
@@ -0,0 +1,183 @@
+/* GMR-1 TCH3 channel coding */
+/* See GMR-1 05.003 (ETSI TS 101 376-5-3 V1.2.1) - Section 5.1 */
+
+/* (C) 2011 by Sylvain Munaut <tnt@246tNt.com>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*! \addtogroup tch3
+ *  @{
+ */
+
+/*! \file l1/tch3.c
+ *  \brief Osmocom GMR-1 TCH3 channel coding implementation
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/gmr1/l1/conv.h>
+#include <osmocom/gmr1/l1/crc.h>
+#include <osmocom/gmr1/l1/punct.h>
+#include <osmocom/gmr1/l1/scramb.h>
+
+
+static struct osmo_conv_code gmr1_conv_tch3_speech;
+
+static void __attribute__ ((constructor))
+gmr1_tch3_init(void)
+{
+	/* Init convolutional coder */
+	memcpy(&gmr1_conv_tch3_speech, &gmr1_conv_tch3, sizeof(struct osmo_conv_code));
+	gmr1_conv_tch3_speech.len = 48;
+	gmr1_puncturer_generate(&gmr1_conv_tch3_speech, &gmr1_punct12_P12);
+}
+
+
+/*! \brief Stateless GMR-1 TCH3 channel coder
+ *  \param[out] bits_e 212 encoded bits to be mapped on a burst
+ *  \param[in] frame0 1st speech frame (10 byte / 80 bits, msb first)
+ *  \param[in] frame1 2nd speech frame (10 byte / 80 bits, msb first)
+ *  \param[in] bits_s 4 status bits to be multiplexed
+ *  \param[in] ciph 208 bits of cipher stream (can be NULL)
+ *  \param[in] m Multiplexing mode (0 or 1)
+ */
+void
+gmr1_tch3_encode(ubit_t *bits_e,
+                 const uint8_t *frame0, const uint8_t *frame1,
+                 const ubit_t *bits_s, const ubit_t *ciph, int m)
+{
+	ubit_t bits_epp[208];
+	ubit_t bits_xmy[208];
+	int i, j;
+
+	for (i=0; i<2; i++)
+	{
+		const uint8_t *frame = i ? frame1 : frame0;
+
+		ubit_t bits_d[80];
+		ubit_t bits_c[104];
+		ubit_t bits_ep[104];
+
+		int kc;
+
+		osmo_pbit2ubit(bits_d, frame, 80);
+
+		osmo_conv_encode(&gmr1_conv_tch3_speech, bits_c, bits_d);
+		memcpy(bits_c+72, bits_d+48, 32);
+
+		for (kc=0; kc<104; kc++) {
+			int ii, ij, kep;
+			ii = kc % 24;
+			ij = kc / 24;
+			kep = (ii < 8) ? (ij + 5*ii) : (ij + 4*ii + 8);
+			bits_ep[kep] = bits_c[kc];
+		}
+
+		if (m) {
+			for (j=0; j<104; j++)
+				bits_epp[(104*i)+j] = bits_ep[j];
+		} else {
+			for (j=0; j<104; j++)
+				bits_epp[(j<<1)+i] = bits_ep[j];
+		}
+	}
+
+	gmr1_scramble_ubit(bits_xmy, bits_epp, 208);
+
+	if (ciph) {
+		for (i=0; i<208; i++)
+			bits_xmy[i] ^= ciph[i];
+	}
+
+	memcpy(bits_e,    bits_xmy,     52);
+	memcpy(bits_e+52, bits_s,        4);
+	memcpy(bits_e+56, bits_xmy+52, 156);
+}
+
+/*! \brief Stateless GMR-1 TCH3 channel decoder
+ *  \param[out] frame0 1st speech frame (10 byte / 80 bits, msb first)
+ *  \param[out] frame1 2nd speech frame (10 byte / 80 bits, msb first)
+ *  \param[out] bits_s 4 status bits that were demultiplexed
+ *  \param[in] bits_e 212 softbits demodulated from a burst
+ *  \param[in] ciph 208 bits of cipher stream (can be NULL)
+ *  \param[in] m Multiplexing mode (0 or 1)
+ *  \param[out] conv0_rv Return of the conv. decode of frame 0 (can be NULL)
+ *  \param[out] conv1_rv Return of the conv. decode of frame 1 (can be NULL)
+ *  \return 0 if CRC check pass, any other value for fail.
+ */
+void
+gmr1_tch3_decode(uint8_t *frame0, uint8_t *frame1, ubit_t *bits_s,
+                 const sbit_t *bits_e, const ubit_t *ciph, int m,
+                 int *conv0_rv, int *conv1_rv)
+{
+	sbit_t bits_xmy[208];
+	sbit_t bits_epp[208];
+	int rv, i, j;
+
+	for (i=0; i<4; i++)
+		bits_s[i] = bits_e[52+i] < 0;
+
+	memcpy(bits_xmy,    bits_e,     52);
+	memcpy(bits_xmy+52, bits_e+56, 156);
+
+	if (ciph) {
+		for (i=0; i<208; i++)
+			if (ciph[i])
+				bits_xmy[i] *= -1;
+	}
+
+	gmr1_scramble_sbit(bits_epp, bits_xmy, 208);
+
+	for (i=0; i<2; i++)
+	{
+		int *conv_rv = i ? conv1_rv : conv0_rv;
+		uint8_t *frame = i ? frame1 : frame0;
+
+		sbit_t bits_ep[104];
+		sbit_t bits_c[104];
+		ubit_t bits_d[80];
+
+		int kc;
+
+		if (m) {
+			for (j=0; j<104; j++)
+				bits_ep[j] = bits_epp[(104*i)+j];
+		} else {
+			for (j=0; j<104; j++)
+				bits_ep[j] = bits_epp[(j<<1)+i];
+		}
+
+		for (kc=0; kc<104; kc++) {
+			int ii, ij, kep;
+			ii = kc % 24;
+			ij = kc / 24;
+			kep = (ii < 8) ? (ij + 5*ii) : (ij + 4*ii + 8);
+			bits_c[kc] = bits_ep[kep];
+		}
+
+		rv = osmo_conv_decode(&gmr1_conv_tch3_speech, bits_c, bits_d);
+		if (conv_rv)
+			*conv_rv = rv;
+
+		for (j=48; j<80; j++)
+			bits_d[j] = bits_c[j+24] < 0;
+
+		osmo_ubit2pbit(frame, bits_d, 80);
+	}
+}
+
+/*! }@ */