diff --git a/src/libmsc/Makefile.am b/src/libmsc/Makefile.am
index de02a17..c7fe4bb 100644
--- a/src/libmsc/Makefile.am
+++ b/src/libmsc/Makefile.am
@@ -27,6 +27,7 @@
 libmsc_a_SOURCES = \
 	call_leg.c \
 	cell_id_list.c \
+	codec_mapping.c \
 	sccp_ran.c \
 	msc_vty.c \
 	db.c \
diff --git a/src/libmsc/codec_mapping.c b/src/libmsc/codec_mapping.c
new file mode 100644
index 0000000..69b8ed1
--- /dev/null
+++ b/src/libmsc/codec_mapping.c
@@ -0,0 +1,521 @@
+/* Routines for translation between codec representations: SDP, CC/BSSMAP variants, MGCP, MNCC */
+/*
+ * (C) 2019-2023 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr
+ *
+ * SPDX-License-Identifier: AGPL-3.0+
+ *
+ * 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/>.
+ */
+#include <string.h>
+
+#include <osmocom/gsm/mncc.h>
+
+#include <osmocom/msc/sdp_msg.h>
+#include <osmocom/msc/codec_mapping.h>
+#include <osmocom/msc/mncc.h>
+
+const struct codec_mapping codec_map[] = {
+	/* FIXME: sdp.fmtp handling is not done properly yet, proper mode-set and octet-align handling will follow in
+	 * separate patches. */
+	{
+		.sdp = {
+			.payload_type = 0,
+			.subtype_name = "PCMU",
+			.rate = 8000,
+		},
+		.mgcp = CODEC_PCMU_8000_1,
+	},
+	{
+		.sdp = {
+			.payload_type = 3,
+			.subtype_name = "GSM",
+			.rate = 8000,
+		},
+		.mgcp = CODEC_GSM_8000_1,
+		.speech_ver_count = 1,
+		.speech_ver = { GSM48_BCAP_SV_FR },
+		.mncc_payload_msg_type = GSM_TCHF_FRAME,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_FR1,
+		},
+		.perm_speech = GSM0808_PERM_FR1,
+		.frhr = CODEC_FRHR_FR,
+	},
+	{
+		.sdp = {
+			.payload_type = 8,
+			.subtype_name = "PCMA",
+			.rate = 8000,
+		},
+		.mgcp = CODEC_PCMA_8000_1,
+	},
+	{
+		.sdp = {
+			.payload_type = 18,
+			.subtype_name = "G729",
+			.rate = 8000,
+		},
+		.mgcp = CODEC_G729_8000_1,
+	},
+	{
+		.sdp = {
+			.payload_type = 110,
+			.subtype_name = "GSM-EFR",
+			.rate = 8000,
+		},
+		.mgcp = CODEC_GSMEFR_8000_1,
+		.speech_ver_count = 1,
+		.speech_ver = { GSM48_BCAP_SV_EFR },
+		.mncc_payload_msg_type = GSM_TCHF_FRAME_EFR,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_FR2,
+		},
+		.perm_speech = GSM0808_PERM_FR2,
+		.frhr = CODEC_FRHR_FR,
+	},
+	{
+		.sdp = {
+			.payload_type = 111,
+			.subtype_name = "GSM-HR-08",
+			.rate = 8000,
+		},
+		.mgcp = CODEC_GSMHR_8000_1,
+		.speech_ver_count = 1,
+		.speech_ver = { GSM48_BCAP_SV_HR },
+		.mncc_payload_msg_type = GSM_TCHH_FRAME,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_HR1,
+			.cfg = GSM0808_SC_CFG_DEFAULT_HR_AMR,
+		},
+		.perm_speech = GSM0808_PERM_HR1,
+		.frhr = CODEC_FRHR_HR,
+	},
+	{
+		.sdp = {
+			.payload_type = 112,
+			.subtype_name = "AMR",
+			.rate = 8000,
+			/* AMR is always octet-aligned in 2G and 3G RAN, so this fmtp is signalled to remote call legs.
+			 * So far, fmtp is ignored in incoming SIP SDP, so an incoming SDP without 'octet-align=1' will
+			 * match with this entry; we will still reply with 'octet-align=1', which often works out. */
+			.fmtp = "octet-align=1",
+		},
+		.mgcp = CODEC_AMR_8000_1,
+		.speech_ver_count = 1,
+		.speech_ver = { GSM48_BCAP_SV_AMR_F },
+		.mncc_payload_msg_type = GSM_TCH_FRAME_AMR,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_FR3,
+			.cfg = GSM0808_SC_CFG_DEFAULT_FR_AMR,
+		},
+		.perm_speech = GSM0808_PERM_FR3,
+		.frhr = CODEC_FRHR_FR,
+	},
+	{
+		/* Another entry like the above, to map HR3 to AMR, too. */
+		.sdp = {
+			.payload_type = 112,
+			.subtype_name = "AMR",
+			.rate = 8000,
+			.fmtp = "octet-align=1",
+		},
+		.mgcp = CODEC_AMR_8000_1,
+		.speech_ver_count = 2,
+		.speech_ver = { GSM48_BCAP_SV_AMR_H, GSM48_BCAP_SV_AMR_OH },
+		.mncc_payload_msg_type = GSM_TCH_FRAME_AMR,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_HR3,
+			.cfg = GSM0808_SC_CFG_DEFAULT_HR_AMR,
+		},
+		.perm_speech = GSM0808_PERM_HR3,
+		.frhr = CODEC_FRHR_HR,
+	},
+	{
+		.sdp = {
+			.payload_type = 113,
+			.subtype_name = "AMR-WB",
+			.rate = 16000,
+			.fmtp = "octet-align=1",
+		},
+		.mgcp = CODEC_AMRWB_16000_1,
+		.speech_ver_count = 2,
+		.speech_ver = { GSM48_BCAP_SV_AMR_OFW, GSM48_BCAP_SV_AMR_FW },
+		.mncc_payload_msg_type = GSM_TCH_FRAME_AMR,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_FR5,
+			.cfg = GSM0808_SC_CFG_DEFAULT_FR_AMR_WB,
+		},
+		.perm_speech = GSM0808_PERM_FR5,
+		.frhr = CODEC_FRHR_FR,
+	},
+	{
+		/* Another entry like the above, to map HR4 to AMR-WB, too. */
+		.sdp = {
+			.payload_type = 113,
+			.subtype_name = "AMR-WB",
+			.rate = 16000,
+			.fmtp = "octet-align=1",
+		},
+		.mgcp = CODEC_AMRWB_16000_1,
+		.speech_ver_count = 1,
+		.speech_ver = { GSM48_BCAP_SV_AMR_OHW },
+		.mncc_payload_msg_type = GSM_TCH_FRAME_AMR,
+		.has_gsm0808_speech_codec = true,
+		.gsm0808_speech_codec = {
+			.fi = true,
+			.type = GSM0808_SCT_HR4,
+			.cfg = GSM0808_SC_CFG_DEFAULT_OHR_AMR_WB,
+		},
+		.perm_speech = GSM0808_PERM_HR4,
+		.frhr = CODEC_FRHR_HR,
+	},
+	{
+		.sdp = {
+			.payload_type = 96,
+			.subtype_name = "VND.3GPP.IUFP",
+			.rate = 16000,
+		},
+		.mgcp = CODEC_IUFP,
+	},
+};
+
+#define foreach_codec_mapping(CODEC_MAPPING) \
+	for ((CODEC_MAPPING) = codec_map; (CODEC_MAPPING) < codec_map + ARRAY_SIZE(codec_map); (CODEC_MAPPING)++)
+
+const struct gsm_mncc_bearer_cap bearer_cap_empty = {
+		.speech_ver = { -1 },
+	};
+
+const struct codec_mapping *codec_mapping_by_speech_ver(enum gsm48_bcap_speech_ver speech_ver)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		int i;
+		for (i = 0; i < m->speech_ver_count; i++)
+			if (m->speech_ver[i] == speech_ver)
+				return m;
+	}
+	return NULL;
+}
+
+const struct codec_mapping *codec_mapping_by_gsm0808_speech_codec_type(enum gsm0808_speech_codec_type sct)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		if (!m->has_gsm0808_speech_codec)
+			continue;
+		if (m->gsm0808_speech_codec.type == sct)
+			return m;
+	}
+	return NULL;
+}
+
+const struct codec_mapping *codec_mapping_by_gsm0808_speech_codec(const struct gsm0808_speech_codec *sc)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		if (!m->has_gsm0808_speech_codec)
+			continue;
+		if (m->gsm0808_speech_codec.type != sc->type)
+			continue;
+		/* Return only those where sc->cfg is a subset of m->gsm0808_speech_codec.cfg. */
+		if ((m->gsm0808_speech_codec.cfg & sc->cfg) != sc->cfg)
+			continue;
+		return m;
+	}
+	return NULL;
+}
+
+const struct codec_mapping *codec_mapping_by_perm_speech(enum gsm0808_permitted_speech perm_speech)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		if (m->perm_speech == perm_speech)
+			return m;
+	}
+	return NULL;
+}
+
+const struct codec_mapping *codec_mapping_by_subtype_name(const char *subtype_name)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		if (!strcmp(m->sdp.subtype_name, subtype_name))
+			return m;
+	}
+	return NULL;
+}
+
+const struct codec_mapping *codec_mapping_by_mgcp_codec(enum mgcp_codecs mgcp)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		if (m->mgcp == mgcp)
+			return m;
+	}
+	return NULL;
+}
+
+/* Append given Speech Version to the end of the Bearer Capabilities Speech Version array. Return 1 if added, zero
+ * otherwise (as in, return the number of items added). */
+int bearer_cap_add_speech_ver(struct gsm_mncc_bearer_cap *bearer_cap, enum gsm48_bcap_speech_ver speech_ver)
+{
+	int i;
+	for (i = 0; i < ARRAY_SIZE(bearer_cap->speech_ver) - 1; i++) {
+		if (bearer_cap->speech_ver[i] == speech_ver)
+			return 0;
+		if (bearer_cap->speech_ver[i] == -1) {
+			bearer_cap->speech_ver[i] = speech_ver;
+			bearer_cap->speech_ver[i+1] = -1;
+			return 1;
+		}
+	}
+	return 0;
+}
+
+/* From the current speech_ver list present in the bearer_cap, set the bearer_cap.radio.
+ * If a HR speech_ver is present, set to GSM48_BCAP_RRQ_DUAL_FR, otherwise set to GSM48_BCAP_RRQ_FR_ONLY. */
+int bearer_cap_set_radio(struct gsm_mncc_bearer_cap *bearer_cap)
+{
+	bool hr_present = false;
+	int i;
+	for (i = 0; i < ARRAY_SIZE(bearer_cap->speech_ver) - 1; i++) {
+		const struct codec_mapping *m;
+
+		if (bearer_cap->speech_ver[i] == -1)
+			break;
+
+		m = codec_mapping_by_speech_ver(bearer_cap->speech_ver[i]);
+
+		if (!m)
+			continue;
+
+		if (m->frhr == CODEC_FRHR_HR)
+			hr_present = true;
+	}
+
+	if (hr_present)
+		bearer_cap->radio = GSM48_BCAP_RRQ_DUAL_FR;
+	else
+		bearer_cap->radio = GSM48_BCAP_RRQ_FR_ONLY;
+
+	return 0;
+}
+
+/* Try to convert the SDP audio codec name to Speech Versions to append to Bearer Capabilities.
+ * Return the number of Speech Version entries added (some may add more than one, others may be unknown/unapplicable and
+ * return 0). */
+int sdp_audio_codec_add_to_bearer_cap(struct gsm_mncc_bearer_cap *bearer_cap, const struct sdp_audio_codec *codec)
+{
+	const struct codec_mapping *m;
+	int added = 0;
+	foreach_codec_mapping(m) {
+		int i;
+		if (strcmp(m->sdp.subtype_name, codec->subtype_name))
+			continue;
+		/* TODO also match rate and fmtp? */
+		for (i = 0; i < m->speech_ver_count; i++)
+			added += bearer_cap_add_speech_ver(bearer_cap, m->speech_ver[i]);
+	}
+	return added;
+}
+
+/* Append all audio codecs found in given sdp_msg to Bearer Capability, by traversing all codec entries with
+ * sdp_audio_codec_add_to_bearer_cap(). Return the number of Speech Version entries added.
+ * Note that Speech Version entries are only appended, no previous entries are removed.
+ * Note that only the Speech Version entries are modified; to make a valid Bearer Capabiliy, at least bearer_cap->radio
+ * must also be set (before or after this function); see also bearer_cap_set_radio(). */
+int sdp_audio_codecs_to_bearer_cap(struct gsm_mncc_bearer_cap *bearer_cap, const struct sdp_audio_codecs *ac)
+{
+	const struct sdp_audio_codec *codec;
+	int added = 0;
+
+	foreach_sdp_audio_codec(codec, ac) {
+		added += sdp_audio_codec_add_to_bearer_cap(bearer_cap, codec);
+	}
+
+	return added;
+}
+
+/* Convert Speech Version to SDP audio codec and append to SDP message struct. */
+struct sdp_audio_codec *sdp_audio_codecs_add_speech_ver(struct sdp_audio_codecs *ac,
+							enum gsm48_bcap_speech_ver speech_ver)
+{
+	const struct codec_mapping *m;
+	struct sdp_audio_codec *ret = NULL;
+	foreach_codec_mapping(m) {
+		int i;
+		for (i = 0; i < m->speech_ver_count; i++) {
+			if (m->speech_ver[i] == speech_ver) {
+				ret = sdp_audio_codecs_add_copy(ac, &m->sdp);
+				break;
+			}
+		}
+	}
+	return ret;
+}
+
+struct sdp_audio_codec *sdp_audio_codecs_add_mgcp_codec(struct sdp_audio_codecs *ac, enum mgcp_codecs mgcp_codec)
+{
+	const struct codec_mapping *m = codec_mapping_by_mgcp_codec(mgcp_codec);
+	if (!m)
+		return NULL;
+	return sdp_audio_codecs_add_copy(ac, &m->sdp);
+}
+
+void sdp_audio_codecs_from_bearer_cap(struct sdp_audio_codecs *ac, const struct gsm_mncc_bearer_cap *bc)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(bc->speech_ver); i++) {
+		if (bc->speech_ver[i] == -1)
+			break;
+		sdp_audio_codecs_add_speech_ver(ac, bc->speech_ver[i]);
+	}
+}
+
+void sdp_audio_codecs_to_speech_codec_list(struct gsm0808_speech_codec_list *scl, const struct sdp_audio_codecs *ac)
+{
+	const struct sdp_audio_codec *codec;
+
+	*scl = (struct gsm0808_speech_codec_list){};
+
+	foreach_sdp_audio_codec(codec, ac) {
+		const struct codec_mapping *m = codec_mapping_by_subtype_name(codec->subtype_name);
+		if (!m)
+			continue;
+		if (!m->has_gsm0808_speech_codec)
+			continue;
+		if (scl->len >= ARRAY_SIZE(scl->codec))
+			break;
+		scl->codec[scl->len] = m->gsm0808_speech_codec;
+		/* FIXME: apply AMR configuration according to codec->fmtp */
+		scl->len++;
+	}
+}
+
+void sdp_audio_codecs_from_speech_codec_list(struct sdp_audio_codecs *ac, const struct gsm0808_speech_codec_list *cl)
+{
+	int i;
+	for (i = 0; i < cl->len; i++) {
+		const struct gsm0808_speech_codec *sc = &cl->codec[i];
+		const struct codec_mapping *m = codec_mapping_by_gsm0808_speech_codec(sc);
+		if (!m)
+			continue;
+		sdp_audio_codecs_add_copy(ac, &m->sdp);
+		/* FIXME: for AMR, apply sc->cfg to the added codec's fmtp */
+	}
+}
+
+int sdp_audio_codecs_to_gsm0808_channel_type(struct gsm0808_channel_type *ct, const struct sdp_audio_codecs *ac)
+{
+	const struct sdp_audio_codec *codec;
+	bool fr_present = false;
+	int first_fr_idx = -1;
+	bool hr_present = false;
+	int first_hr_idx = -1;
+	int idx = -1;
+
+	*ct = (struct gsm0808_channel_type){
+		.ch_indctr = GSM0808_CHAN_SPEECH,
+	};
+
+	foreach_sdp_audio_codec(codec, ac) {
+		const struct codec_mapping *m;
+		int i;
+		bool dup;
+		idx++;
+		foreach_codec_mapping(m) {
+			if (strcmp(m->sdp.subtype_name, codec->subtype_name))
+				continue;
+
+			switch (m->perm_speech) {
+			default:
+				continue;
+
+			case GSM0808_PERM_FR1:
+			case GSM0808_PERM_FR2:
+			case GSM0808_PERM_FR3:
+			case GSM0808_PERM_FR4:
+			case GSM0808_PERM_FR5:
+				fr_present = true;
+				if (first_fr_idx < 0)
+					first_fr_idx = idx;
+				break;
+
+			case GSM0808_PERM_HR1:
+			case GSM0808_PERM_HR2:
+			case GSM0808_PERM_HR3:
+			case GSM0808_PERM_HR4:
+			case GSM0808_PERM_HR6:
+				hr_present = true;
+				if (first_hr_idx < 0)
+					first_hr_idx = idx;
+				break;
+			}
+
+			/* Avoid duplicates */
+			dup = false;
+			for (i = 0; i < ct->perm_spch_len; i++) {
+				if (ct->perm_spch[i] == m->perm_speech) {
+					dup = true;
+					break;
+				}
+			}
+			if (dup)
+				continue;
+
+			ct->perm_spch[ct->perm_spch_len] = m->perm_speech;
+			ct->perm_spch_len++;
+		}
+	}
+
+	if (fr_present && hr_present) {
+		if (first_fr_idx <= first_hr_idx)
+			ct->ch_rate_type = GSM0808_SPEECH_FULL_PREF;
+		else
+			ct->ch_rate_type = GSM0808_SPEECH_HALF_PREF;
+	} else if (fr_present && !hr_present)
+		ct->ch_rate_type = GSM0808_SPEECH_FULL_BM;
+	else if (!fr_present && hr_present)
+		ct->ch_rate_type = GSM0808_SPEECH_HALF_LM;
+	else
+		return -EINVAL;
+	return 0;
+}
+
+enum mgcp_codecs sdp_audio_codec_to_mgcp_codec(const struct sdp_audio_codec *codec)
+{
+	const struct codec_mapping *m;
+	foreach_codec_mapping(m) {
+		if (!sdp_audio_codec_cmp(&m->sdp, codec, false, false))
+			return m->mgcp;
+	}
+	return NO_MGCP_CODEC;
+}