diff --git a/lib/decoding/osmocom/codec/gsm620.c b/lib/decoding/osmocom/codec/gsm620.c
new file mode 100644
index 0000000..282781f
--- /dev/null
+++ b/lib/decoding/osmocom/codec/gsm620.c
@@ -0,0 +1,297 @@
+/*! \file gsm620.c
+ * GSM 06.20 - GSM HR 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 HR unvoiced (mode=0) frames - subjective importance bit ordering */
+	/* This array encode mapping between GSM 05.03 Table 3a (bits
+	 * ordering before channel coding on TCH) and GSM 06.20 Table B.1
+	 * (bit ordering on A-bis */
+const uint16_t gsm620_unvoiced_bitorder[112] = {
+	3,	/* R0:1 */
+	25,	/* LPC 3:7 */
+	52,	/* GSP 0-1:2 */
+	71,	/* GSP 0-2:2 */
+	90,	/* GSP 0-3:2 */
+	109,	/* GSP 0-4:2 */
+	15,	/* LPC 1:0 */
+	19,	/* LPC 2:5 */
+	20,	/* LPC 2:4 */
+	21,	/* LPC 2:3 */
+	22,	/* LPC 2:2 */
+	23,	/* LPC 2:1 */
+	26,	/* LPC 3:6 */
+	27,	/* LPC 3:5 */
+	28,	/* LPC 3:4 */
+	29,	/* LPC 3:3 */
+	30,	/* LPC 3:2 */
+	31,	/* LPC 3:1 */
+	61,	/* Code 1-2:0 */
+	62,	/* Code 2-2:6 */
+	63,	/* Code 2-2:5 */
+	64,	/* Code 2-2:4 */
+	65,	/* Code 2-2:3 */
+	66,	/* Code 2-2:2 */
+	67,	/* Code 2-2:1 */
+	68,	/* Code 2-2:0 */
+	74,	/* Code 1-3:6 */
+	75,	/* Code 1-3:5 */
+	76,	/* Code 1-3:4 */
+	77,	/* Code 1-3:3 */
+	78,	/* Code 1-3:2 */
+	79,	/* Code 1-3:1 */
+	80,	/* Code 1-3:0 */
+	81,	/* Code 2-3:6 */
+	82,	/* Code 2-3:5 */
+	83,	/* Code 2-3:4 */
+	84,	/* Code 2-3:3 */
+	32,	/* LPC 3:0 */
+	4,	/* R0:0 */
+	33,	/* INT-LPC:0 */
+	60,	/* Code 1-2:1 */
+	59,	/* Code 1-2:2 */
+	58,	/* Code 1-2:3 */
+	57,	/* Code 1-2:4 */
+	56,	/* Code 1-2:5 */
+	55,	/* Code 1-2:6 */
+	49,	/* Code 2-1:0 */
+	48,	/* Code 2-1:1 */
+	47,	/* Code 2-1:2 */
+	46,	/* Code 2-1:3 */
+	45,	/* Code 2-1:4 */
+	44,	/* Code 2-1:5 */
+	43,	/* Code 2-1:6 */
+	42,	/* Code 1-1:0 */
+	41,	/* Code 1-1:1 */
+	40,	/* Code 1-1:2 */
+	39,	/* Code 1-1:3 */
+	38,	/* Code 1-1:4 */
+	37,	/* Code 1-1:5 */
+	36,	/* Code 1-1:6 */
+	111,	/* GSP 0-4:0 */
+	92,	/* GSP 0-3:0 */
+	73,	/* GSP 0-2:0 */
+	54,	/* GSP 0-1:0 */
+	24,	/* LPC 2:0 */
+	110,	/* GSP 0-4:1 */
+	91,	/* GSP 0-3:1 */
+	72,	/* GSP 0-2:1 */
+	53,	/* GSP 0-1:1 */
+	14,	/* LPC 1:1 */
+	13,	/* LPC 1:2 */
+	12,	/* LPC 1:3 */
+	11,	/* LPC 1:4 */
+	10,	/* LPC 1:5 */
+	108,	/* GSP 0-4:3 */
+	89,	/* GSP 0-3:3 */
+	70,	/* GSP 0-2:3 */
+	51,	/* GSP 0-1:3 */
+	16,	/* LPC 2:8 */
+	17,	/* LPC 2:7 */
+	18,	/* LPC 2:6 */
+	107,	/* GSP 0-4:4 */
+	88,	/* GSP 0-3:4 */
+	69,	/* GSP 0-2:4 */
+	50,	/* GSP 0-1:4 */
+	9,	/* LPC 1:6 */
+	8,	/* LPC 1:7 */
+	7,	/* LPC 1:8 */
+	6,	/* LPC 1:9 */
+	2,	/* R0:2 */
+	5,	/* LPC 1:10 */
+	1,	/* R0:3 */
+	0,	/* R0:4 */
+	35,	/* Mode:0 */
+	34,	/* Mode:1 */
+	106,	/* Code 2-4:0 */
+	105,	/* Code 2-4:1 */
+	104,	/* Code 2-4:2 */
+	103,	/* Code 2-4:3 */
+	102,	/* Code 2-4:4 */
+	101,	/* Code 2-4:5 */
+	100,	/* Code 2-4:6 */
+	99,	/* Code 1-4:0 */
+	98,	/* Code 1-4:1 */
+	97,	/* Code 1-4:2 */
+	96,	/* Code 1-4:3 */
+	95,	/* Code 1-4:4 */
+	94,	/* Code 1-4:5 */
+	93,	/* Code 1-4:6 */
+	87,	/* Code 2-3:0 */
+	86,	/* Code 2-3:1 */
+	85,	/* Code 2-3:2 */
+};
+
+/* GSM HR voiced (mode=1,2,3) frames - subjective importance bit ordering */
+	/* This array encode mapping between GSM 05.03 Table 3b (bits
+	 * ordering before channel coding on TCH) and GSM 06.20 Table B.2
+	 * (bit ordering on A-bis */
+const uint16_t gsm620_voiced_bitorder[112] = {
+	13,	/* LPC 1:2 */
+	14,	/* LPC 1:1 */
+	18,	/* LPC 2:6 */
+	19,	/* LPC 2:5 */
+	20,	/* LPC 2:4 */
+	53,	/* GSP 0-1:4 */
+	71,	/* GSP 0-2:4 */
+	89,	/* GSP 0-3:4 */
+	107,	/* GSP 0-4:4 */
+	54,	/* GSP 0-1:3 */
+	72,	/* GSP 0-2:3 */
+	90,	/* GSP 0-3:3 */
+	108,	/* GSP 0-4:3 */
+	55,	/* GSP 0-1:2 */
+	73,	/* GSP 0-2:2 */
+	91,	/* GSP 0-3:2 */
+	109,	/* GSP 0-4:2 */
+	44,	/* Code 1:8 */
+	45,	/* Code 1:7 */
+	46,	/* Code 1:6 */
+	47,	/* Code 1:5 */
+	48,	/* Code 1:4 */
+	49,	/* Code 1:3 */
+	50,	/* Code 1:2 */
+	51,	/* Code 1:1 */
+	52,	/* Code 1:0 */
+	62,	/* Code 2:8 */
+	63,	/* Code 2:7 */
+	64,	/* Code 2:6 */
+	65,	/* Code 2:5 */
+	68,	/* Code 2:2 */
+	69,	/* Code 2:1 */
+	70,	/* Code 2:0 */
+	80,	/* Code 3:8 */
+	66,	/* Code 2:4 */
+	67,	/* Code 2:3 */
+	56,	/* GSP 0-1:1 */
+	74,	/* GSP 0-2:1 */
+	92,	/* GSP 0-3:1 */
+	110,	/* GSP 0-4:1 */
+	57,	/* GSP 0-1:0 */
+	75,	/* GSP 0-2:0 */
+	93,	/* GSP 0-3:0 */
+	111,	/* GSP 0-4:0 */
+	33,	/* INT-LPC:0 */
+	24,	/* LPC 2:0 */
+	32,	/* LPC 3:0 */
+	97,	/* LAG 4:0 */
+	31,	/* LPC 3:1 */
+	23,	/* LPC 2:1 */
+	96,	/* LAG 4:1 */
+	79,	/* LAG 3:0 */
+	61,	/* LAG 2:0 */
+	43,	/* LAG 1:0 */
+	95,	/* LAG 4:2 */
+	78,	/* LAG 3:1 */
+	60,	/* LAG 2:1 */
+	42,	/* LAG 1:1 */
+	30,	/* LPC 3:2 */
+	29,	/* LPC 3:3 */
+	28,	/* LPC 3:4 */
+	22,	/* LPC 2:2 */
+	27,	/* LPC 3:5 */
+	26,	/* LPC 3:6 */
+	21,	/* LPC 2:3 */
+	4,	/* R0:0 */
+	25,	/* LPC 3:7 */
+	15,	/* LPC 1:0 */
+	94,	/* LAG 4:3 */
+	77,	/* LAG 3:2 */
+	59,	/* LAG 2:2 */
+	41,	/* LAG 1:2 */
+	3,	/* R0:1 */
+	76,	/* LAG 3:3 */
+	58,	/* LAG 2:3 */
+	40,	/* LAG 1:3 */
+	39,	/* LAG 1:4 */
+	17,	/* LPC 2:7 */
+	16,	/* LPC 2:8 */
+	12,	/* LPC 1:3 */
+	11,	/* LPC 1:4 */
+	10,	/* LPC 1:5 */
+	9,	/* LPC 1:6 */
+	2,	/* R0:2 */
+	38,	/* LAG 1:5 */
+	37,	/* LAG 1:6 */
+	36,	/* LAG 1:7 */
+	8,	/* LPC 1:7 */
+	7,	/* LPC 1:8 */
+	6,	/* LPC 1:9 */
+	5,	/* LPC 1:10 */
+	1,	/* R0:3 */
+	0,	/* R0:4 */
+	35,	/* Mode:0 */
+	34,	/* Mode:1 */
+	106,	/* Code 4:0 */
+	105,	/* Code 4:1 */
+	104,	/* Code 4:2 */
+	103,	/* Code 4:3 */
+	102,	/* Code 4:4 */
+	101,	/* Code 4:5 */
+	100,	/* Code 4:6 */
+	99,	/* Code 4:7 */
+	98,	/* Code 4:8 */
+	88,	/* Code 3:0 */
+	87,	/* Code 3:1 */
+	86,	/* Code 3:2 */
+	85,	/* Code 3:3 */
+	84,	/* Code 3:4 */
+	83,	/* Code 3:5 */
+	82,	/* Code 3:6 */
+	81,	/* Code 3:7 */
+};
+
+static inline uint16_t mask(const uint8_t msb)
+{
+	const uint16_t m = (uint16_t)1  << (msb - 1);
+	return (m - 1) ^ m;
+}
+
+/*! Check whether RTP frame contains HR SID code word according to
+ *  TS 101 318 §5.2.2
+ *  \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_hr_check_sid(const uint8_t *rtp_payload, size_t payload_len)
+{
+	uint8_t i, bits[] = { 1, 2, 8, 9, 5, 4, 9, 5, 4, 9, 5, 4, 9, 5 };
+	struct bitvec bv;
+	bv.data = (uint8_t *) rtp_payload;
+	bv.data_len = payload_len;
+	bv.cur_bit = 33;
+
+	/* code word is all 1 at given bits, numbered from 1, MODE is always 3 */
+	for (i = 0; i < ARRAY_SIZE(bits); i++)
+		if (bitvec_get_uint(&bv, bits[i]) != mask(bits[i]))
+			return false;
+
+	return true;
+}