wipneels/amr_fmtp

Change-Id: I00a410e0c01a527d7bbd978da91649f4fdf6775c

9 files changed, 135 insertions, 84 deletions

diff --git a/include/osmocom/msc/codec_mapping.h b/include/osmocom/msc/codec_mapping.h
index 7781dfce2..7f5e33982 100644
--- a/include/osmocom/msc/codec_mapping.h
+++ b/include/osmocom/msc/codec_mapping.h
@@ -96,3 +96,6 @@ int sdp_audio_codecs_to_gsm0808_channel_type(struct gsm0808_channel_type *ct, co
 enum mgcp_codecs sdp_audio_codec_to_mgcp_codec(const struct osmo_sdp_codec *codec);
 
 char *sdp_codec_to_str(const struct osmo_sdp_codec *codec);
+char *sdp_msg_to_str(const struct osmo_sdp_msg *msg, bool summarize);
+
+void sdp_msg_replace(void *ctx, struct osmo_sdp_msg **var, struct osmo_sdp_msg *new_msg);
diff --git a/include/osmocom/msc/sdp_msg.h b/include/osmocom/msc/sdp_msg.h
index 4a42ab9d8..475191164 100644
--- a/include/osmocom/msc/sdp_msg.h
+++ b/include/osmocom/msc/sdp_msg.h
@@ -3,4 +3,4 @@
 #include <osmocom/sdp/sdp_msg.h>
 #include <osmocom/msc/csd_bs.h>
 
-void sdp_codecs_set_csd(void *ctx, struct osmo_sdp_codec_list *codecs);
+void sdp_codecs_set_csd(void *ctx, struct osmo_sdp_codec_list **codecs);
diff --git a/include/osmocom/msc/transaction.h b/include/osmocom/msc/transaction.h
index 33e435a5d..24845d997 100644
--- a/include/osmocom/msc/transaction.h
+++ b/include/osmocom/msc/transaction.h
@@ -131,13 +131,14 @@ struct gsm_trans {
 			bool mncc_initiated;	/* Whether an MNCC Release is necessary on failure */
 			struct osmo_lcls *lcls;
 			/* SDP as last received from the remote call leg. */
-			struct osmo_sdp_msg remote;
+			struct osmo_sdp_msg *remote;
 			/* Track codec/CSD choices from BSS and remote call leg */
-			struct codec_filter codecs;
+			struct codec_filter *codec_filter;
 			struct csd_filter csd;
 			/* Resulting choice from codecs/bearer services and the
 			 * local RTP address to be sent to the remote call leg. */
-			struct osmo_sdp_msg local;
+			struct osmo_sdp_msg *local;
+			struct csd_bs_list local_bearer_services;
 		} cc;
 		struct {
 			struct gsm411_smc_inst smc_inst;
diff --git a/src/libmsc/codec_mapping.c b/src/libmsc/codec_mapping.c
index d47d74a4e..82e479768 100644
--- a/src/libmsc/codec_mapping.c
+++ b/src/libmsc/codec_mapping.c
@@ -437,19 +437,19 @@ int bearer_cap_set_radio(struct gsm_mncc_bearer_cap *bearer_cap)
 /* 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)
+int sdp_audio_codec_add_to_bearer_cap(struct gsm_mncc_bearer_cap *bearer_cap, const struct osmo_sdp_codec *codec)
 {
 	const struct codec_mapping *m;
 	int added = 0;
-	LOGP(DLGLOBAL, LOGL_ERROR, "sdp_audio_codec_add_to_bearer_cap(%s)\n", sdp_audio_codec_to_str(codec));
+	LOGP(DLGLOBAL, LOGL_ERROR, "sdp_audio_codec_add_to_bearer_cap(%s)\n", sdp_codec_to_str(codec));
 	codec_mapping_foreach(m) {
 		int i;
 		if (osmo_sdp_codec_cmp(&m->sdp, codec, &osmo_sdp_codec_cmp_equivalent))
 			continue;
-		LOGP(DLGLOBAL, LOGL_ERROR, " %s speech_ver_count %d\n", sdp_audio_codec_to_str(&m->sdp),
+		LOGP(DLGLOBAL, LOGL_ERROR, " %s speech_ver_count %d\n", sdp_codec_to_str(&m->sdp),
 		     m->speech_ver_count);
 		for (i = 0; i < m->speech_ver_count; i++) {
-			LOGP(DLGLOBAL, LOGL_ERROR, " - add %s  (enum gsm48_bcap_speech_ver)%d\n", sdp_audio_codec_to_str(&m->sdp),
+			LOGP(DLGLOBAL, LOGL_ERROR, " - add %s  (enum gsm48_bcap_speech_ver)%d\n", sdp_codec_to_str(&m->sdp),
 			     m->speech_ver[i]);
 			added += bearer_cap_add_speech_ver(bearer_cap, m->speech_ver[i]);
 		}
@@ -513,14 +513,14 @@ void sdp_audio_codecs_from_bearer_cap(struct osmo_sdp_codec_list *codecs, const
 /* Append an entry for the given sdp_audio_codec to the gsm0808_speech_codec_list.
  * Return 0 if an entry was added, -ENOENT when there is no mapping to gsm0808_speech_codec for the given
  * sdp_audio_codec, and -ENOSPC when scl is full and nothing could be added. */
-int sdp_audio_codec_to_speech_codec_list(struct gsm0808_speech_codec_list *scl, const struct sdp_audio_codec *codec)
+int sdp_audio_codec_to_speech_codec_list(struct gsm0808_speech_codec_list *scl, const struct osmo_sdp_codec *codec)
 {
 	const struct codec_mapping *m;
 	int added = 0;
 	int i;
 
 	codec_mapping_foreach (m) {
-		if (sdp_audio_codec_cmp(&m->sdp, codec, true, false))
+		if (osmo_sdp_codec_cmp(&m->sdp, codec, &osmo_sdp_codec_cmp_equivalent))
 			continue;
 		if (!m->has_gsm0808_speech_codec)
 			continue;
@@ -555,20 +555,20 @@ int sdp_audio_codec_to_speech_codec_list(struct gsm0808_speech_codec_list *scl,
 	return 0;
 }
 
-void sdp_audio_codecs_to_speech_codec_list(struct gsm0808_speech_codec_list *scl, const struct sdp_audio_codecs *ac)
+void sdp_audio_codecs_to_speech_codec_list(struct gsm0808_speech_codec_list *scl, const struct osmo_sdp_codec_list *ac)
 {
-	const struct sdp_audio_codec *codec;
+	const struct osmo_sdp_codec *codec;
 
 	*scl = (struct gsm0808_speech_codec_list){};
 
-	sdp_audio_codecs_foreach(codec, ac) {
+	osmo_sdp_codec_list_foreach(codec, ac) {
 		int rc = sdp_audio_codec_to_speech_codec_list(scl, codec);
 		if (rc == -ENOSPC)
 			break;
 	}
 }
 
-void sdp_audio_codecs_from_speech_codec_list(struct sdp_audio_codecs *ac, const struct gsm0808_speech_codec_list *cl)
+void sdp_audio_codecs_from_speech_codec_list(struct osmo_sdp_codec_list *ac, const struct gsm0808_speech_codec_list *cl)
 {
 	int i;
 	for (i = 0; i < cl->len; i++) {
@@ -583,9 +583,9 @@ void sdp_audio_codecs_from_speech_codec_list(struct sdp_audio_codecs *ac, const
 	}
 }
 
-int sdp_audio_codecs_to_gsm0808_channel_type(struct gsm0808_channel_type *ct, const struct sdp_audio_codecs *ac)
+int sdp_audio_codecs_to_gsm0808_channel_type(struct gsm0808_channel_type *ct, const struct osmo_sdp_codec_list *ac)
 {
-	const struct sdp_audio_codec *codec;
+	const struct osmo_sdp_codec *codec;
 	bool fr_present = false;
 	int first_fr_idx = -1;
 	bool hr_present = false;
@@ -597,19 +597,19 @@ int sdp_audio_codecs_to_gsm0808_channel_type(struct gsm0808_channel_type *ct, co
 	};
 	LOGP(DLGLOBAL, LOGL_ERROR, "sdp_audio_codecs_to_gsm0808_channel_type()\n");
 
-	sdp_audio_codecs_foreach(codec, ac) {
+	osmo_sdp_codec_list_foreach(codec, ac) {
 		const struct codec_mapping *m;
 		int i;
 		bool dup;
 		idx++;
 
-		LOGP(DLGLOBAL, LOGL_ERROR, "- codec = %s\n", sdp_audio_codec_to_str(codec));
+		LOGP(DLGLOBAL, LOGL_ERROR, "- codec = %s\n", sdp_codec_to_str(codec));
 
 		codec_mapping_foreach(m) {
-			LOGP(DLGLOBAL, LOGL_ERROR, "   (m=%s %s)\n", sdp_audio_codec_to_str(&m->sdp),
+			LOGP(DLGLOBAL, LOGL_ERROR, "   (m=%s %s)\n", sdp_codec_to_str(&m->sdp),
 			     gsm0808_permitted_speech_name(m->perm_speech));
 
-			if (sdp_audio_codec_cmp(codec, &m->sdp, true, false))
+			if (osmo_sdp_codec_cmp(codec, &m->sdp, &osmo_sdp_codec_cmp_equivalent))
 				continue;
 
 			switch (m->perm_speech) {
@@ -668,11 +668,11 @@ int sdp_audio_codecs_to_gsm0808_channel_type(struct gsm0808_channel_type *ct, co
 	return 0;
 }
 
-enum mgcp_codecs sdp_audio_codec_to_mgcp_codec(const struct sdp_audio_codec *codec)
+enum mgcp_codecs sdp_audio_codec_to_mgcp_codec(const struct osmo_sdp_codec *codec)
 {
 	const struct codec_mapping *m;
 	codec_mapping_foreach(m) {
-		if (!sdp_audio_codec_cmp(&m->sdp, codec, true, false))
+		if (!osmo_sdp_codec_cmp(&m->sdp, codec, &osmo_sdp_codec_cmp_equivalent))
 			return m->mgcp;
 	}
 	return NO_MGCP_CODEC;
@@ -682,3 +682,21 @@ char *sdp_codec_to_str(const struct osmo_sdp_codec *codec)
 {
 	return osmo_sdp_codec_to_str_c(OTC_SELECT, codec);
 }
+
+char *sdp_msg_to_str(const struct osmo_sdp_msg *msg, bool summarize)
+{
+	return osmo_sdp_msg_to_str_c(OTC_SELECT, msg, summarize);
+}
+
+void sdp_msg_replace(void *ctx, struct osmo_sdp_msg **var, struct osmo_sdp_msg *new_msg)
+{
+	struct osmo_sdp_msg *msg = *var;
+	if (msg)
+		talloc_free(msg);
+	msg = new_msg;
+	if (msg)
+		talloc_steal(ctx, msg);
+	else
+		msg = osmo_sdp_msg_alloc(ctx);
+	*var = msg;
+}
diff --git a/src/libmsc/csd_filter.c b/src/libmsc/csd_filter.c
index d1dcda927..a6ce9fdc2 100644
--- a/src/libmsc/csd_filter.c
+++ b/src/libmsc/csd_filter.c
@@ -98,7 +98,7 @@ int csd_filter_run(struct csd_filter *filter, struct osmo_sdp_msg *sdp_result, s
 		csd_bs_list_add_bs(r, a);
 	}
 
-	sdp_codecs_set_csd(sdp_result, &result->codecs);
+	sdp_codecs_set_csd(sdp_result, &sdp_result->codecs);
 	return 0;
 }
 
@@ -107,7 +107,7 @@ int csd_filter_to_str_buf(char *buf, size_t buflen, const struct csd_filter *fil
 			    const struct osmo_sdp_msg *result, const struct osmo_sdp_msg *remote)
 {
 	struct osmo_strbuf sb = { .buf = buf, .len = buflen };
-	OSMO_STRBUF_APPEND(sb, sdp_msg_to_str_buf, result);
+	OSMO_STRBUF_APPEND(sb, osmo_sdp_msg_to_str_buf, result, false);
 	OSMO_STRBUF_PRINTF(sb, " (from:");
 
 	if (filter->assignment) {
@@ -115,9 +115,9 @@ int csd_filter_to_str_buf(char *buf, size_t buflen, const struct csd_filter *fil
 		OSMO_STRBUF_APPEND(sb, csd_bs_to_str_buf, filter->assignment);
 	}
 
-	if (remote->bearer_services.count || osmo_sockaddr_str_is_nonzero(&remote->rtp)) {
+	if (!osmo_sdp_codec_list_is_empty(remote->codecs) || osmo_sockaddr_str_is_nonzero(&remote->rtp)) {
 		OSMO_STRBUF_PRINTF(sb, " remote=");
-		OSMO_STRBUF_APPEND(sb, sdp_msg_to_str_buf, remote);
+		OSMO_STRBUF_APPEND(sb, osmo_sdp_msg_to_str_buf, remote, true);
 	}
 
 	if (filter->ms.count) {
diff --git a/src/libmsc/gsm_04_08_cc.c b/src/libmsc/gsm_04_08_cc.c
index 49a583f3d..96ab99817 100644
--- a/src/libmsc/gsm_04_08_cc.c
+++ b/src/libmsc/gsm_04_08_cc.c
@@ -240,7 +240,7 @@ static void _log_mncc_rx_tx(const char *file, int line,
 			    struct gsm_trans *trans, const char *rx_tx, const union mncc_msg *mncc)
 {
 	const char *sdp = NULL;
-	struct osmo_sdp_msg sdp_msg = {};
+	struct osmo_sdp_msg *sdp_msg = NULL;
 	struct osmo_sockaddr addr = {};
 
 	if (!log_check_level(DMNCC, LOGL_DEBUG))
@@ -271,19 +271,20 @@ static void _log_mncc_rx_tx(const char *file, int line,
 	}
 
 	if (sdp && sdp[0]) {
-		int rc = sdp_msg_from_sdp_str(&sdp_msg, sdp);
-		if (rc != 0) {
-			LOG_TRANS_CAT_SRC(trans, DMNCC, LOGL_ERROR, file, line, "%s %s: invalid SDP message (trying anyway)\n",
+		struct osmo_sdp_err err;
+		sdp_msg = osmo_sdp_msg_decode(OTC_SELECT, sdp, &err);
+		if (err.rc != 0) {
+			LOG_TRANS_CAT_SRC(trans, DMNCC, LOGL_ERROR, file, line,
+					  "%s %s: invalid SDP message (trying anyway): %s\n",
 					  rx_tx,
-					  get_mncc_name(mncc->msg_type));
-			LOG_TRANS_CAT_SRC(trans, DMNCC, LOGL_DEBUG, file, line, "erratic SDP: %s\n",
-					  osmo_quote_cstr_c(OTC_SELECT, sdp, -1));
+					  get_mncc_name(mncc->msg_type),
+					  osmo_quote_cstr_c(OTC_SELECT, err.src_str, err.src_str_len));
 			return;
 		}
 		LOG_TRANS_CAT_SRC(trans, DMNCC, LOGL_DEBUG, file, line, "%s %s (RTP=%s)\n",
 				  rx_tx,
 				  get_mncc_name(mncc->msg_type),
-				  sdp_msg_to_str(&sdp_msg));
+				  sdp_msg_to_str(sdp_msg, false));
 		return;
 	}
 
@@ -754,10 +755,10 @@ void gsm48_cc_rx_setup_cn_local_rtp_port_known(struct gsm_trans *trans)
 		trans_free(trans);
 		return;
 	}
-	trans->cc.local.rtp = *rtp_cn_local;
+	trans->cc.local->rtp = *rtp_cn_local;
 
-	sdp = trans->cc.local.audio_codecs.count ? &trans->cc.local : NULL;
-	rc = sdp_msg_to_sdp_str_buf(setup.sdp, sizeof(setup.sdp), sdp);
+	sdp = osmo_sdp_codec_list_is_empty(trans->cc.local->codecs) ? NULL : trans->cc.local;
+	rc = osmo_sdp_msg_encode_buf(setup.sdp, sizeof(setup.sdp), sdp);
 	if (rc >= sizeof(setup.sdp)) {
 		LOG_TRANS(trans, LOGL_ERROR, "MNCC_SETUP_IND: SDP too long (%d > %zu bytes)\n", rc, sizeof(setup.sdp));
 		trans_free(trans);
@@ -768,14 +769,22 @@ void gsm48_cc_rx_setup_cn_local_rtp_port_known(struct gsm_trans *trans)
 	mncc_recvmsg(trans->net, trans, MNCC_SETUP_IND, &setup);
 }
 
-static bool codecs_match(const struct sdp_audio_codec *a, const struct sdp_audio_codec *b)
+static bool codecs_match(const struct osmo_sdp_codec *a, const struct osmo_sdp_codec *b)
 {
-	if (!sdp_audio_codec_cmp(a, b, true, false))
+	if (!osmo_sdp_codec_cmp(a, b, &osmo_sdp_codec_cmp_equivalent))
 		return true;
 
 	/* Codecs are not identical. But will the MGW be able to transcode? */
-	if (!strcmp("AMR", a->subtype_name) && !strcmp("AMR", b->subtype_name)) {
-		/* TODO: compare matching mode-set. */
+	if (!strcmp("AMR", a->encoding_name) && !strcmp("AMR", b->encoding_name)) {
+		/* MGW is expected to even out octet-align=0 vs 1 mismatches, so do not compare AMR octet-align. */
+
+		/* FIXME: compare matching mode-set.
+		 * So far regarding any and all mode-sets as equivalent.
+		 * Instead, a well-guided 'false' here may help to switch the BSS to an FR channel if the remote side
+		 * cannot do any HR rates. */
+
+		/* TODO: any other important AMR fmtp parameters? So far we've only ever seen 'octet-align' and
+		 * 'mode-set' in practice. So far regard all of them as not important for codec matching. */
 		return true;
 	}
 	return false;
@@ -784,43 +793,48 @@ static bool codecs_match(const struct sdp_audio_codec *a, const struct sdp_audio
 static void rx_mncc_sdp(struct gsm_trans *trans, uint32_t mncc_msg_type, const char *sdp,
 			const struct gsm_mncc_bearer_cap *bcap)
 {
-	struct codec_filter *codecs = &trans->cc.codecs;
+	struct codec_filter *codecs = trans->cc.codec_filter;
 	struct call_leg *cl = trans->msc_a ? trans->msc_a->cc.call_leg : NULL;
 	struct rtp_stream *rtp_cn = cl ? cl->rtp[RTP_TO_CN] : NULL;
 
 	if (sdp[0]) {
-		int rc = sdp_msg_from_sdp_str(&trans->cc.remote, sdp);
-		if (rc)
-			LOG_TRANS_CAT(trans, DMNCC, LOGL_ERROR, "rx %s: Failed to parse SDP: %d. Trying anyway.\n",
-				      get_mncc_name(mncc_msg_type), rc);
+		struct osmo_sdp_err err;
+		struct osmo_sdp_msg *msg = osmo_sdp_msg_decode(OTC_SELECT, sdp, &err);
+		if (err.rc)
+			LOG_TRANS_CAT(trans, DMNCC, LOGL_ERROR,
+				      "rx %s: Failed to parse SDP, trying anyway: %d at %s\n",
+				      get_mncc_name(mncc_msg_type), err.rc,
+				      osmo_quote_cstr_c(OTC_SELECT, err.src_str, err.src_str_len));
+		else if (msg)
+			sdp_msg_replace(trans, &trans->cc.remote, msg);
 	}
 
 	/* if there is no SDP information or we failed to parse it, try using the Bearer Cap from MNCC, if any. */
-	if (!trans->cc.remote.audio_codecs.count && bcap) {
-		trans->cc.remote = (struct osmo_sdp_msg){};
+	if (bcap && (!trans->cc.remote || osmo_sdp_codec_list_is_empty(trans->cc.remote->codecs))) {
+		sdp_msg_replace(trans, &trans->cc.remote, NULL);
 		trans_cc_set_remote_from_bc(trans, bcap);
 		LOG_TRANS_CAT(trans, DMNCC, LOGL_DEBUG, "rx %s Bearer Cap: remote=%s\n",
-			      get_mncc_name(mncc_msg_type), sdp_msg_to_str(&trans->cc.remote));
+			      get_mncc_name(mncc_msg_type), sdp_msg_to_str(trans->cc.remote, false));
 	}
 
-	if (!trans->cc.remote.audio_codecs.count)
+	if (!trans->cc.remote || osmo_sdp_codec_list_is_empty(trans->cc.remote->codecs))
 		LOG_TRANS(trans, LOGL_INFO,
 			  "Got no information of remote audio codecs: neither SDP nor Bearer Capability. Trying anyway.\n");
 
 	trans_cc_filter_run(trans);
 	if (rtp_cn) {
-		rtp_stream_set_remote_addr_and_codecs(rtp_cn, &trans->cc.remote);
+		rtp_stream_set_remote_addr_and_codecs(rtp_cn, trans->cc.remote);
 		rtp_stream_commit(rtp_cn);
 	}
 
 	/* See if we need to switch codecs to maintain TFO: has the remote side changed the codecs information? If we
 	 * have already assigned a specific codec here, but the remote call leg has now chosen a different codec, we
 	 * need to re-assign this call leg to match the remote leg. */
-	if (!sdp_audio_codec_is_set(&codecs->assignment)) {
+	if (!osmo_sdp_codec_is_set(codecs->assignment)) {
 		/* Voice channel assignment has not completed. Do not interfere. */
 		return;
 	}
-	if (!trans->cc.remote.audio_codecs.count) {
+	if (!trans->cc.remote || osmo_sdp_codec_list_is_empty(trans->cc.remote->codecs)) {
 		/* Don't know remote codecs, nothing to do. */
 		return;
 	}
@@ -833,13 +847,13 @@ static void rx_mncc_sdp(struct gsm_trans *trans, uint32_t mncc_msg_type, const c
 	 * single codec in the SDP; but at least MO *must* send all possible codecs along, to give MT a chance to find a
 	 * good match. Maybe MO should offer all supported codecs, but MT should limit to a single pick -- but what do
 	 * other SDP peers do, say via SIP? */
-	if (codecs_match(&trans->cc.remote.audio_codecs.codec[0], &codecs->assignment))
+	if (codecs_match(osmo_sdp_codec_list_first(trans->cc.remote->codecs), codecs->assignment))
 		return;
 
 	/* We've already completed Assignment of a voice channel (some time ago), and now the remote side has changed
 	 * to a mismatching codec (list). Try to re-assign this side to a matching codec. */
 	LOG_TRANS(trans, LOGL_INFO, "Remote call leg mismatches assigned codec: %s\n",
-		  codec_filter_to_str(&trans->cc.codecs, &trans->cc.local, &trans->cc.remote));
+		  codec_filter_to_str(trans->cc.codec_filter, trans->cc.local, trans->cc.remote));
 	msc_a_tx_assignment_cmd(trans->msc_a);
 }
 
@@ -908,14 +922,14 @@ static int gsm48_cc_tx_setup(struct gsm_trans *trans, void *arg)
 	case GSM48_BCAP_ITCAP_FAX_G3:
 	case GSM48_BCAP_ITCAP_UNR_DIG_INF:
 		if (setup->fields & MNCC_F_BEARER_CAP) {
-			trans->cc.remote = (struct osmo_sdp_msg){};
+			sdp_msg_replace(trans, &trans->cc.remote, NULL);
 			trans_cc_set_remote_from_bc(trans, &setup->bearer_cap);
 			LOG_TRANS_CAT(trans, DMNCC, LOGL_DEBUG, "rx %s Bearer Cap: remote=%s\n",
-				      get_mncc_name(setup->msg_type), sdp_msg_to_str(&trans->cc.remote));
+				      get_mncc_name(setup->msg_type), sdp_msg_to_str(trans->cc.remote, false));
 		} else {
 			LOG_TRANS(trans, LOGL_INFO,
 				  "Got no information of remote Bearer Capability. Trying anyway.\n");
-			sdp_audio_codecs_set_csd(trans, &trans->cc.codecs.ms);
+			sdp_codecs_set_csd(trans->cc.codec_filter, &trans->cc.codec_filter->ms);
 		}
 		trans_cc_filter_run(trans);
 		break;
@@ -933,7 +947,7 @@ static int gsm48_cc_tx_setup(struct gsm_trans *trans, void *arg)
 		bearer_cap = (struct gsm_mncc_bearer_cap){
 			.speech_ver = { -1 },
 		};
-		sdp_audio_codecs_to_bearer_cap(&bearer_cap, &trans->cc.local.audio_codecs);
+		sdp_audio_codecs_to_bearer_cap(&bearer_cap, trans->cc.local->codecs);
 		rc = bearer_cap_set_radio(&bearer_cap);
 		if (rc) {
 			LOG_TRANS(trans, LOGL_ERROR, "Error composing Bearer Capability for CC Setup\n");
@@ -947,7 +961,7 @@ static int gsm48_cc_tx_setup(struct gsm_trans *trans, void *arg)
 		if (bearer_cap.speech_ver[0] == -1) {
 			LOG_TRANS(trans, LOGL_ERROR, "%s: no codec match possible: %s\n",
 				  get_mncc_name(setup->msg_type),
-				  codec_filter_to_str(&trans->cc.codecs, &trans->cc.local, &trans->cc.remote));
+				  codec_filter_to_str(trans->cc.codec_filter, trans->cc.local, trans->cc.remote));
 
 			/* incompatible codecs */
 			rc = mncc_release_ind(trans->net, trans, trans->callref,
@@ -962,7 +976,7 @@ static int gsm48_cc_tx_setup(struct gsm_trans *trans, void *arg)
 	case GSM48_BCAP_ITCAP_3k1_AUDIO:
 	case GSM48_BCAP_ITCAP_FAX_G3:
 	case GSM48_BCAP_ITCAP_UNR_DIG_INF:
-		if (csd_bs_list_to_bearer_cap(&bearer_cap, &trans->cc.local.bearer_services) == 0) {
+		if (csd_bs_list_to_bearer_cap(&bearer_cap, &trans->cc.local_bearer_services) == 0) {
 			LOG_TRANS(trans, LOGL_ERROR, "Error composing Bearer Capability for CC Setup\n");
 
 			/* incompatible codecs */
@@ -1109,7 +1123,7 @@ static int gsm48_cc_mt_rtp_port_and_codec_known(struct gsm_trans *trans)
 		trans_free(trans);
 		return -EINVAL;
 	}
-	trans->cc.local.rtp = *rtp_cn_local;
+	trans->cc.local->rtp = *rtp_cn_local;
 
 	trans_cc_filter_run(trans);
 
@@ -2165,7 +2179,7 @@ int gsm48_tch_rtp_create(struct gsm_trans *trans)
 	struct osmo_sockaddr_str *rtp_cn_local;
 	struct rtp_stream *rtp_cn = cl ? cl->rtp[RTP_TO_CN] : NULL;
 	int mncc_payload_msg_type;
-	struct sdp_audio_codec *codec;
+	struct osmo_sdp_codec *codec;
 	const struct codec_mapping *m;
 	struct sdp_audio_codecs *codecs;
 
diff --git a/src/libmsc/msc_vty.c b/src/libmsc/msc_vty.c
index bc03d897a..75561d5b4 100644
--- a/src/libmsc/msc_vty.c
+++ b/src/libmsc/msc_vty.c
@@ -797,7 +797,7 @@ DEFUN_ATTR(cfg_codecs_clear, cfg_codecs_clear_cmd,
 	   CMD_ATTR_IMMEDIATE)
 {
 	struct ran_infra *dst = vty->index;
-	dst->codecs = (struct sdp_audio_codecs){};
+	osmo_sdp_codec_list_free_items(dst->codecs);
 	return CMD_SUCCESS;
 }
 
@@ -816,18 +816,22 @@ DEFUN_ATTR(cfg_codecs_entry, cfg_codecs_entry_cmd,
 	struct ran_infra *dst = vty->index;
 	const char *add_del = argv[0];
 	const char *codec_str = argv[1];
-	struct sdp_audio_codec c;
-	struct sdp_audio_codec *exists;
+	struct osmo_sdp_codec *c;
+	struct osmo_sdp_codec *i;
+	struct osmo_sdp_codec *exists;
 	const struct codec_mapping *m;
 	bool ok;
 
-	if (sdp_audio_codec_from_str(&c, codec_str))
+	c = osmo_sdp_codec_alloc(OTC_SELECT);
+	if (osmo_sdp_codec_from_str(c, codec_str, -1)) {
+		vty_out(vty, "%% Error: cannot parse codec string '%s'%s", codec_str, VTY_NEWLINE);
 		return CMD_WARNING;
+	}
 
 	/* make sure this is a known codec */
 	ok = false;
 	codec_mapping_foreach (m) {
-		if (sdp_audio_codec_cmp(&m->sdp, &c, true, false))
+		if (osmo_sdp_codec_cmp(&m->sdp, c, &osmo_sdp_codec_cmp_equivalent))
 			continue;
 		ok = true;
 		break;
@@ -838,39 +842,42 @@ DEFUN_ATTR(cfg_codecs_entry, cfg_codecs_entry_cmd,
 		return CMD_WARNING;
 	}
 
-	exists = sdp_audio_codecs_by_descr(&dst->codecs, &c);
+	exists = NULL;
+	osmo_sdp_codec_list_foreach (i, dst->codecs) {
+		if (osmo_sdp_codec_cmp(i, c, &osmo_sdp_codec_cmp_equivalent))
+			continue;
+		exists = i;
+		break;
+	}
 
 	if (!strcmp("add", add_del)) {
 		if (exists) {
-			vty_out(vty, "%% Codec already present in the list: %s%s", sdp_audio_codec_to_str(exists),
+			vty_out(vty, "%% Codec already present in the list: %s%s", sdp_codec_to_str(exists),
 				VTY_NEWLINE);
 			return CMD_WARNING;
 		}
 
-		if (!sdp_audio_codecs_add_copy(&dst->codecs, &c, false, false)) {
-			vty_out(vty, "%% Error: failed to add codec '%s' -- too many entries?%s", codec_str, VTY_NEWLINE);
-			return CMD_WARNING;
-		}
+		osmo_sdp_codec_list_add(dst->codecs, c, NULL, false);
 	} else {
 		/* "del" */
 		if (!exists) {
 			vty_out(vty, "%% Codec not present in the list: %s%s", codec_str, VTY_NEWLINE);
 			return CMD_WARNING;
 		}
-		sdp_audio_codecs_remove(&dst->codecs, exists);
+
+		osmo_sdp_codec_list_remove_entry(exists);
+		talloc_free(exists);
 	}
 	return CMD_SUCCESS;
 }
 
 static void config_write_codecs_for_rat(struct vty *vty, enum osmo_rat_type rat)
 {
-	const struct sdp_audio_codec *c;
-	char buf[128];
+	const struct osmo_sdp_codec *c;
 	vty_out(vty, "codecs %s%s", rat == OSMO_RAT_GERAN_A ? "a" : "iu", VTY_NEWLINE);
 	vty_out(vty, " clear%s", VTY_NEWLINE);
-	sdp_audio_codecs_foreach (c, &msc_ran_infra[rat].codecs) {
-		sdp_audio_codec_to_str_buf(buf, sizeof(buf), c);
-		vty_out(vty, " %s%s", buf, VTY_NEWLINE);
+	osmo_sdp_codec_list_foreach (c, msc_ran_infra[rat].codecs) {
+		vty_out(vty, " %s%s", sdp_codec_to_str(c), VTY_NEWLINE);
 	}
 }
 
@@ -899,7 +906,7 @@ DEFUN(show_codecs, show_codecs_cmd,
 		const struct codec_mapping *m;
 		vty_out(vty, "Supported codecs are:%s", VTY_NEWLINE);
 		codec_mapping_foreach (m)
-			vty_out(vty, "  %s%s", sdp_audio_codec_to_str(&m->sdp), VTY_NEWLINE);
+			vty_out(vty, "  %s%s", sdp_codec_to_str(&m->sdp), VTY_NEWLINE);
 	}
 	return CMD_SUCCESS;
 }
diff --git a/src/libmsc/sdp_msg.c b/src/libmsc/sdp_msg.c
index c9b5c16c0..0d88fe89a 100644
--- a/src/libmsc/sdp_msg.c
+++ b/src/libmsc/sdp_msg.c
@@ -29,8 +29,11 @@ static const struct osmo_sdp_codec codec_csd = {
 	.rate = 8000,
 };
 
-void sdp_codecs_set_csd(void *ctx, struct osmo_sdp_codec_list *codecs)
+void sdp_codecs_set_csd(void *ctx, struct osmo_sdp_codec_list **codecs)
 {
-	osmo_sdp_codec_list_free(codecs);
-	osmo_sdp_codec_list_add(ctx, &codec_csd);
+	if (*codecs)
+		osmo_sdp_codec_list_free_items(*codecs);
+	else
+		*codecs = osmo_sdp_codec_list_alloc(ctx);
+	osmo_sdp_codec_list_add(*codecs, &codec_csd);
 }
diff --git a/src/libmsc/transaction.c b/src/libmsc/transaction.c
index 7ae4c7d92..4fe816bbf 100644
--- a/src/libmsc/transaction.c
+++ b/src/libmsc/transaction.c
@@ -225,6 +225,11 @@ struct gsm_trans *trans_alloc(struct gsm_network *net,
 	};
 	if (vsub)
 		vlr_subscr_get(vsub, trans_vsub_use(type));
+	if (type == TRANS_CC) {
+		trans->cc.codec_filter = talloc_zero(trans, struct codec_filter);
+		trans->cc.remote = osmo_sdp_codec_alloc(trans);
+		trans->cc.local = osmo_sdp_codec_alloc(trans);
+	}
 	llist_add_tail(&trans->entry, &net->trans_list);
 
 	LOG_TRANS(trans, LOGL_DEBUG, "New transaction\n");