diff --git a/lib/decoding/osmocom/codec/gsm610.c b/lib/decoding/osmocom/codec/gsm610.c
new file mode 100644
index 0000000..a05eaba
--- /dev/null
+++ b/lib/decoding/osmocom/codec/gsm610.c
@@ -0,0 +1,336 @@
+/*! \file gsm610.c
+ * GSM 06.10 - GSM FR codec. */
+/*
+ * (C) 2010 Sylvain Munaut <tnt@246tNt.com>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * 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 <stdint.h>
+#include <stdbool.h>
+
+#include <osmocom/core/bitvec.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/codec/codec.h>
+
+/* GSM FR - subjective importance bit ordering */
+	/* This array encodes GSM 05.03 Table 2.
+	 * It's also GSM 06.10 Table A.2.1a
+	 *
+	 * It converts between serial parameter output by the encoder and the
+	 * order needed before channel encoding.
+	 */
+const uint16_t gsm610_bitorder[260] = {
+	0,	/* LARc0:5 */
+	47,	/* Xmaxc0:5 */
+	103,	/* Xmaxc1:5 */
+	159,	/* Xmaxc2:5 */
+	215,	/* Xmaxc3:5 */
+	1,	/* LARc0:4 */
+	6,	/* LARc1:5 */
+	12,	/* LARc2:4 */
+	2,	/* LARc0:3 */
+	7,	/* LARc1:4 */
+	13,	/* LARc2:3 */
+	17,	/* LARc3:4 */
+	36,	/* Nc0:6 */
+	92,	/* Nc1:6 */
+	148,	/* Nc2:6 */
+	204,	/* Nc3:6 */
+	48,	/* Xmaxc0:4 */
+	104,	/* Xmaxc1:4 */
+	160,	/* Xmaxc2:4 */
+	216,	/* Xmaxc3:4 */
+	8,	/* LARc1:3 */
+	22,	/* LARc4:3 */
+	26,	/* LARc5:3 */
+	37,	/* Nc0:5 */
+	93,	/* Nc1:5 */
+	149,	/* Nc2:5 */
+	205,	/* Nc3:5 */
+	38,	/* Nc0:4 */
+	94,	/* Nc1:4 */
+	150,	/* Nc2:4 */
+	206,	/* Nc3:4 */
+	39,	/* Nc0:3 */
+	95,	/* Nc1:3 */
+	151,	/* Nc2:3 */
+	207,	/* Nc3:3 */
+	40,	/* Nc0:2 */
+	96,	/* Nc1:2 */
+	152,	/* Nc2:2 */
+	208,	/* Nc3:2 */
+	49,	/* Xmaxc0:3 */
+	105,	/* Xmaxc1:3 */
+	161,	/* Xmaxc2:3 */
+	217,	/* Xmaxc3:3 */
+	3,	/* LARc0:2 */
+	18,	/* LARc3:3 */
+	30,	/* LARc6:2 */
+	41,	/* Nc0:1 */
+	97,	/* Nc1:1 */
+	153,	/* Nc2:1 */
+	209,	/* Nc3:1 */
+	23,	/* LARc4:2 */
+	27,	/* LARc5:2 */
+	43,	/* bc0:1 */
+	99,	/* bc1:1 */
+	155,	/* bc2:1 */
+	211,	/* bc3:1 */
+	42,	/* Nc0:0 */
+	98,	/* Nc1:0 */
+	154,	/* Nc2:0 */
+	210,	/* Nc3:0 */
+	45,	/* Mc0:1 */
+	101,	/* Mc1:1 */
+	157,	/* Mc2:1 */
+	213,	/* Mc3:1 */
+	4,	/* LARc0:1 */
+	9,	/* LARc1:2 */
+	14,	/* LARc2:2 */
+	33,	/* LARc7:2 */
+	19,	/* LARc3:2 */
+	24,	/* LARc4:1 */
+	31,	/* LARc6:1 */
+	44,	/* bc0:0 */
+	100,	/* bc1:0 */
+	156,	/* bc2:0 */
+	212,	/* bc3:0 */
+	50,	/* Xmaxc0:2 */
+	106,	/* Xmaxc1:2 */
+	162,	/* Xmaxc2:2 */
+	218,	/* Xmaxc3:2 */
+	53,	/* xmc0_0:2 */
+	56,	/* xmc0_1:2 */
+	59,	/* xmc0_2:2 */
+	62,	/* xmc0_3:2 */
+	65,	/* xmc0_4:2 */
+	68,	/* xmc0_5:2 */
+	71,	/* xmc0_6:2 */
+	74,	/* xmc0_7:2 */
+	77,	/* xmc0_8:2 */
+	80,	/* xmc0_9:2 */
+	83,	/* xmc0_10:2 */
+	86,	/* xmc0_11:2 */
+	89,	/* xmc0_12:2 */
+	109,	/* xmc1_0:2 */
+	112,	/* xmc1_1:2 */
+	115,	/* xmc1_2:2 */
+	118,	/* xmc1_3:2 */
+	121,	/* xmc1_4:2 */
+	124,	/* xmc1_5:2 */
+	127,	/* xmc1_6:2 */
+	130,	/* xmc1_7:2 */
+	133,	/* xmc1_8:2 */
+	136,	/* xmc1_9:2 */
+	139,	/* xmc1_10:2 */
+	142,	/* xmc1_11:2 */
+	145,	/* xmc1_12:2 */
+	165,	/* xmc2_0:2 */
+	168,	/* xmc2_1:2 */
+	171,	/* xmc2_2:2 */
+	174,	/* xmc2_3:2 */
+	177,	/* xmc2_4:2 */
+	180,	/* xmc2_5:2 */
+	183,	/* xmc2_6:2 */
+	186,	/* xmc2_7:2 */
+	189,	/* xmc2_8:2 */
+	192,	/* xmc2_9:2 */
+	195,	/* xmc2_10:2 */
+	198,	/* xmc2_11:2 */
+	201,	/* xmc2_12:2 */
+	221,	/* xmc3_0:2 */
+	224,	/* xmc3_1:2 */
+	227,	/* xmc3_2:2 */
+	230,	/* xmc3_3:2 */
+	233,	/* xmc3_4:2 */
+	236,	/* xmc3_5:2 */
+	239,	/* xmc3_6:2 */
+	242,	/* xmc3_7:2 */
+	245,	/* xmc3_8:2 */
+	248,	/* xmc3_9:2 */
+	251,	/* xmc3_10:2 */
+	254,	/* xmc3_11:2 */
+	257,	/* xmc3_12:2 */
+	46,	/* Mc0:0 */
+	102,	/* Mc1:0 */
+	158,	/* Mc2:0 */
+	214,	/* Mc3:0 */
+	51,	/* Xmaxc0:1 */
+	107,	/* Xmaxc1:1 */
+	163,	/* Xmaxc2:1 */
+	219,	/* Xmaxc3:1 */
+	54,	/* xmc0_0:1 */
+	57,	/* xmc0_1:1 */
+	60,	/* xmc0_2:1 */
+	63,	/* xmc0_3:1 */
+	66,	/* xmc0_4:1 */
+	69,	/* xmc0_5:1 */
+	72,	/* xmc0_6:1 */
+	75,	/* xmc0_7:1 */
+	78,	/* xmc0_8:1 */
+	81,	/* xmc0_9:1 */
+	84,	/* xmc0_10:1 */
+	87,	/* xmc0_11:1 */
+	90,	/* xmc0_12:1 */
+	110,	/* xmc1_0:1 */
+	113,	/* xmc1_1:1 */
+	116,	/* xmc1_2:1 */
+	119,	/* xmc1_3:1 */
+	122,	/* xmc1_4:1 */
+	125,	/* xmc1_5:1 */
+	128,	/* xmc1_6:1 */
+	131,	/* xmc1_7:1 */
+	134,	/* xmc1_8:1 */
+	137,	/* xmc1_9:1 */
+	140,	/* xmc1_10:1 */
+	143,	/* xmc1_11:1 */
+	146,	/* xmc1_12:1 */
+	166,	/* xmc2_0:1 */
+	169,	/* xmc2_1:1 */
+	172,	/* xmc2_2:1 */
+	175,	/* xmc2_3:1 */
+	178,	/* xmc2_4:1 */
+	181,	/* xmc2_5:1 */
+	184,	/* xmc2_6:1 */
+	187,	/* xmc2_7:1 */
+	190,	/* xmc2_8:1 */
+	193,	/* xmc2_9:1 */
+	196,	/* xmc2_10:1 */
+	199,	/* xmc2_11:1 */
+	202,	/* xmc2_12:1 */
+	222,	/* xmc3_0:1 */
+	225,	/* xmc3_1:1 */
+	228,	/* xmc3_2:1 */
+	231,	/* xmc3_3:1 */
+	234,	/* xmc3_4:1 */
+	237,	/* xmc3_5:1 */
+	240,	/* xmc3_6:1 */
+	243,	/* xmc3_7:1 */
+	246,	/* xmc3_8:1 */
+	249,	/* xmc3_9:1 */
+	252,	/* xmc3_10:1 */
+	255,	/* xmc3_11:1 */
+	258,	/* xmc3_12:1 */
+	5,	/* LARc0:0 */
+	10,	/* LARc1:1 */
+	15,	/* LARc2:1 */
+	28,	/* LARc5:1 */
+	32,	/* LARc6:0 */
+	34,	/* LARc7:1 */
+	35,	/* LARc7:0 */
+	16,	/* LARc2:0 */
+	20,	/* LARc3:1 */
+	21,	/* LARc3:0 */
+	25,	/* LARc4:0 */
+	52,	/* Xmaxc0:0 */
+	108,	/* Xmaxc1:0 */
+	164,	/* Xmaxc2:0 */
+	220,	/* Xmaxc3:0 */
+	55,	/* xmc0_0:0 */
+	58,	/* xmc0_1:0 */
+	61,	/* xmc0_2:0 */
+	64,	/* xmc0_3:0 */
+	67,	/* xmc0_4:0 */
+	70,	/* xmc0_5:0 */
+	73,	/* xmc0_6:0 */
+	76,	/* xmc0_7:0 */
+	79,	/* xmc0_8:0 */
+	82,	/* xmc0_9:0 */
+	85,	/* xmc0_10:0 */
+	88,	/* xmc0_11:0 */
+	91,	/* xmc0_12:0 */
+	111,	/* xmc1_0:0 */
+	114,	/* xmc1_1:0 */
+	117,	/* xmc1_2:0 */
+	120,	/* xmc1_3:0 */
+	123,	/* xmc1_4:0 */
+	126,	/* xmc1_5:0 */
+	129,	/* xmc1_6:0 */
+	132,	/* xmc1_7:0 */
+	135,	/* xmc1_8:0 */
+	138,	/* xmc1_9:0 */
+	141,	/* xmc1_10:0 */
+	144,	/* xmc1_11:0 */
+	147,	/* xmc1_12:0 */
+	167,	/* xmc2_0:0 */
+	170,	/* xmc2_1:0 */
+	173,	/* xmc2_2:0 */
+	176,	/* xmc2_3:0 */
+	179,	/* xmc2_4:0 */
+	182,	/* xmc2_5:0 */
+	185,	/* xmc2_6:0 */
+	188,	/* xmc2_7:0 */
+	191,	/* xmc2_8:0 */
+	194,	/* xmc2_9:0 */
+	197,	/* xmc2_10:0 */
+	200,	/* xmc2_11:0 */
+	203,	/* xmc2_12:0 */
+	223,	/* xmc3_0:0 */
+	226,	/* xmc3_1:0 */
+	229,	/* xmc3_2:0 */
+	232,	/* xmc3_3:0 */
+	235,	/* xmc3_4:0 */
+	238,	/* xmc3_5:0 */
+	241,	/* xmc3_6:0 */
+	244,	/* xmc3_7:0 */
+	247,	/* xmc3_8:0 */
+	250,	/* xmc3_9:0 */
+	253,	/* xmc3_10:0 */
+	256,	/* xmc3_11:0 */
+	259,	/* xmc3_12:0 */
+	11,	/* LARc1:0 */
+	29,	/* LARc5:0 */
+};
+
+/*! Check whether RTP frame contains FR SID code word according to
+ *  TS 101 318 §5.1.2
+ *  \param[in] rtp_payload Buffer with RTP payload
+ *  \param[in] payload_len Length of payload
+ *  \returns true if code word is found, false otherwise
+ */
+bool osmo_fr_check_sid(const uint8_t *rtp_payload, size_t payload_len)
+{
+	struct bitvec bv;
+	uint16_t i, z_bits[] = { 57, 58, 60, 61, 63, 64, 66, 67, 69, 70, 72, 73,
+				 75, 76, 78, 79, 81, 82, 84, 85, 87, 88, 90, 91,
+				 93, 94, 113, 114, 116, 117, 119, 120, 122, 123,
+				 125, 126, 128, 129, 131, 132, 134, 135, 137,
+				 138, 140, 141, 143, 144, 146, 147, 149, 150,
+				 169, 170, 172, 173, 175, 176, 178, 179, 181,
+				 182, 184, 185, 187, 188, 190, 191, 193, 194,
+				 196, 197, 199, 200, 202, 203, 205, 206, 225,
+				 226, 228, 229, 231, 232, 234, 235, 237, 240,
+				 243, 246, 249, 252, 255, 258, 261 };
+
+	/* signature does not match Full Rate SID */
+	if ((rtp_payload[0] >> 4) != 0xD)
+		return false;
+
+	bv.data = (uint8_t *) rtp_payload;
+	bv.data_len = payload_len;
+
+	/* code word is all 0 at given bits, numbered from 1 */
+	for (i = 0; i < ARRAY_SIZE(z_bits); i++)
+		if (bitvec_get_bit_pos(&bv, z_bits[i]) != ZERO)
+			return false;
+
+	return true;
+}