rtp_engine.c: Initial split of payload types into rx and tx mappings.

There are numerous problems with the current implementation of the RTP
payload type mapping in Asterisk.  It uses only one mapping structure to
associate payload types to codecs.  The single mapping is overkill if all
of the payload type values are well known values.  Dynamic payload type
mappings do not work as well with the single mapping because RFC3264
allows each side of the link to negotiate different dynamic mappings for
what they want to receive.  Not only could you have the same codec mapped
for sending and receiving on different payload types you could wind up
with the same payload type mapped to different codecs for each direction.

1) An independent payload type mapping is needed for sending and
receiving.

2) The receive mapping needs to keep track of previous mappings because of
the slack to when negotiation happens and current packets in flight using
the old mapping arrive.

3) The transmit mapping only needs to keep track of the current negotiated
values since we are sending the packets and know when the switchover takes
place.

* Needed to create ast_rtp_codecs_payload_code_tx() and make some callers
use the new function because ast_rtp_codecs_payload_code() was used for
mappings in both directions.

* Needed to create ast_rtp_codecs_payloads_xover() for cases where we need
to pass preferred codec mappings to the peer channel for early media
bridging or when we need to prefer the offered mapping that RFC3264 says
we SHOULD use.

* ast_rtp_codecs_payloads_xover() and ast_rtp_codecs_payload_code_tx() are
the only new public functions created.  All the others were only used for
the tx or rx mapping direction so the function doxygen now reflects which
direction the function operates.

* chan_mgcp.c: Removed call to ast_rtp_codecs_payloads_clear() as doing
that makes no sense when processing an incoming SDP.  We would be wiping
out any mappings that we set for the possible outgoing SDP we sent
earlier.

ASTERISK-25166
Reported by: Kevin Harwell

ASTERISK-17410
Reported by: Boris Fox

Change-Id: Iaf6c227bca68cb7c414cf2fd4108a8ac98bd45ac

1 files changed, 421 insertions, 76 deletions

diff --git a/main/rtp_engine.c b/main/rtp_engine.c
index 1375897d6..229af8fc9 100644
--- a/main/rtp_engine.c
+++ b/main/rtp_engine.c
@@ -580,22 +580,32 @@ int ast_rtp_codecs_payloads_initialize(struct ast_rtp_codecs *codecs)
 
 	codecs->framing = 0;
 	ast_rwlock_init(&codecs->codecs_lock);
-	res = AST_VECTOR_INIT(&codecs->payloads, AST_RTP_MAX_PT);
+	res = AST_VECTOR_INIT(&codecs->payload_mapping_rx, AST_RTP_MAX_PT);
+	res |= AST_VECTOR_INIT(&codecs->payload_mapping_tx, AST_RTP_MAX_PT);
+	if (res) {
+		AST_VECTOR_FREE(&codecs->payload_mapping_rx);
+		AST_VECTOR_FREE(&codecs->payload_mapping_tx);
+	}
 
 	return res;
 }
 
 void ast_rtp_codecs_payloads_destroy(struct ast_rtp_codecs *codecs)
 {
-	int i;
+	int idx;
+	struct ast_rtp_payload_type *type;
 
-	for (i = 0; i < AST_VECTOR_SIZE(&codecs->payloads); i++) {
-		struct ast_rtp_payload_type *type;
+	for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_rx); ++idx) {
+		type = AST_VECTOR_GET(&codecs->payload_mapping_rx, idx);
+		ao2_t_cleanup(type, "destroying ast_rtp_codec rx mapping");
+	}
+	AST_VECTOR_FREE(&codecs->payload_mapping_rx);
 
-		type = AST_VECTOR_GET(&codecs->payloads, i);
-		ao2_t_cleanup(type, "destroying ast_rtp_codec");
+	for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_tx); ++idx) {
+		type = AST_VECTOR_GET(&codecs->payload_mapping_tx, idx);
+		ao2_t_cleanup(type, "destroying ast_rtp_codec tx mapping");
 	}
-	AST_VECTOR_FREE(&codecs->payloads);
+	AST_VECTOR_FREE(&codecs->payload_mapping_tx);
 
 	ast_rwlock_destroy(&codecs->codecs_lock);
 }
@@ -613,34 +623,254 @@ void ast_rtp_codecs_payloads_clear(struct ast_rtp_codecs *codecs, struct ast_rtp
 	}
 }
 
-void ast_rtp_codecs_payloads_copy(struct ast_rtp_codecs *src, struct ast_rtp_codecs *dest, struct ast_rtp_instance *instance)
+/*!
+ * \internal
+ * \brief Clear the rx primary mapping flag on all other matching mappings.
+ * \since 14.0.0
+ *
+ * \param codecs Codecs that need rx clearing.
+ * \param to_match Payload type object to compare against.
+ *
+ * \note It is assumed that codecs is write locked before calling.
+ *
+ * \return Nothing
+ */
+static void payload_mapping_rx_clear_primary(struct ast_rtp_codecs *codecs, struct ast_rtp_payload_type *to_match)
 {
-	int i;
+	int idx;
+	struct ast_rtp_payload_type *current;
+	struct ast_rtp_payload_type *new_type;
+
+	if (!to_match->primary_mapping) {
+		return;
+	}
+
+	for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_rx); ++idx) {
+		current = AST_VECTOR_GET(&codecs->payload_mapping_rx, idx);
+
+		if (!current || current == to_match || !current->primary_mapping) {
+			continue;
+		}
+		if (current->asterisk_format && to_match->asterisk_format) {
+			if (ast_format_cmp(current->format, to_match->format) == AST_FORMAT_CMP_NOT_EQUAL) {
+				continue;
+			}
+		} else if (!current->asterisk_format && !to_match->asterisk_format) {
+			if (current->rtp_code != to_match->rtp_code) {
+				continue;
+			}
+		} else {
+			continue;
+		}
+
+		/* Replace current with non-primary marked version */
+		new_type = ast_rtp_engine_alloc_payload_type();
+		if (!new_type) {
+			continue;
+		}
+		*new_type = *current;
+		new_type->primary_mapping = 0;
+		ao2_bump(new_type->format);
+		AST_VECTOR_REPLACE(&codecs->payload_mapping_rx, idx, new_type);
+		ao2_ref(current, -1);
+	}
+}
+
+/*!
+ * \internal
+ * \brief Copy the rx payload type mapping to the destination.
+ * \since 14.0.0
+ *
+ * \param src The source codecs structure
+ * \param dest The destination codecs structure that the values from src will be copied to
+ * \param instance Optionally the instance that the dst codecs structure belongs to
+ *
+ * \note It is assumed that src is at least read locked before calling.
+ * \note It is assumed that dest is write locked before calling.
+ *
+ * \return Nothing
+ */
+static void rtp_codecs_payloads_copy_rx(struct ast_rtp_codecs *src, struct ast_rtp_codecs *dest, struct ast_rtp_instance *instance)
+{
+	int idx;
+	struct ast_rtp_payload_type *type;
+
+	for (idx = 0; idx < AST_VECTOR_SIZE(&src->payload_mapping_rx); ++idx) {
+		type = AST_VECTOR_GET(&src->payload_mapping_rx, idx);
+		if (!type) {
+			continue;
+		}
+
+		ast_debug(2, "Copying rx payload mapping %d (%p) from %p to %p\n",
+			idx, type, src, dest);
+		ao2_ref(type, +1);
+		if (idx < AST_VECTOR_SIZE(&dest->payload_mapping_rx)) {
+			ao2_t_cleanup(AST_VECTOR_GET(&dest->payload_mapping_rx, idx),
+				"cleaning up rx mapping vector element about to be replaced");
+		}
+		AST_VECTOR_REPLACE(&dest->payload_mapping_rx, idx, type);
+
+		payload_mapping_rx_clear_primary(dest, type);
+
+		if (instance && instance->engine && instance->engine->payload_set) {
+			instance->engine->payload_set(instance, idx, type->asterisk_format, type->format, type->rtp_code);
+		}
+	}
+}
+
+/*!
+ * \internal
+ * \brief Remove other matching payload mappings.
+ * \since 14.0.0
+ *
+ * \param codecs Codecs that need tx mappings removed.
+ * \param instance RTP instance to notify of any payloads removed.
+ * \param to_match Payload type object to compare against.
+ *
+ * \note It is assumed that codecs is write locked before calling.
+ *
+ * \return Nothing
+ */
+static void payload_mapping_tx_remove_other_mappings(struct ast_rtp_codecs *codecs, struct ast_rtp_instance *instance, struct ast_rtp_payload_type *to_match)
+{
+	int idx;
+	struct ast_rtp_payload_type *current;
+
+	for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_tx); ++idx) {
+		current = AST_VECTOR_GET(&codecs->payload_mapping_tx, idx);
+
+		if (!current || current == to_match) {
+			continue;
+		}
+		if (current->asterisk_format && to_match->asterisk_format) {
+			if (ast_format_cmp(current->format, to_match->format) == AST_FORMAT_CMP_NOT_EQUAL) {
+				continue;
+			}
+		} else if (!current->asterisk_format && !to_match->asterisk_format) {
+			if (current->rtp_code != to_match->rtp_code) {
+				continue;
+			}
+		} else {
+			continue;
+		}
+
+		/* Remove other mapping */
+		AST_VECTOR_REPLACE(&codecs->payload_mapping_tx, idx, NULL);
+		ao2_ref(current, -1);
+		if (instance && instance->engine && instance->engine->payload_set) {
+			instance->engine->payload_set(instance, idx, 0, NULL, 0);
+		}
+	}
+}
+
+/*!
+ * \internal
+ * \brief Copy the tx payload type mapping to the destination.
+ * \since 14.0.0
+ *
+ * \param src The source codecs structure
+ * \param dest The destination codecs structure that the values from src will be copied to
+ * \param instance Optionally the instance that the dst codecs structure belongs to
+ *
+ * \note It is assumed that src is at least read locked before calling.
+ * \note It is assumed that dest is write locked before calling.
+ *
+ * \return Nothing
+ */
+static void rtp_codecs_payloads_copy_tx(struct ast_rtp_codecs *src, struct ast_rtp_codecs *dest, struct ast_rtp_instance *instance)
+{
+	int idx;
+	struct ast_rtp_payload_type *type;
+
+	for (idx = 0; idx < AST_VECTOR_SIZE(&src->payload_mapping_tx); ++idx) {
+		type = AST_VECTOR_GET(&src->payload_mapping_tx, idx);
+		if (!type) {
+			continue;
+		}
+
+		ast_debug(2, "Copying tx payload mapping %d (%p) from %p to %p\n",
+			idx, type, src, dest);
+		ao2_ref(type, +1);
+		if (idx < AST_VECTOR_SIZE(&dest->payload_mapping_tx)) {
+			ao2_t_cleanup(AST_VECTOR_GET(&dest->payload_mapping_tx, idx),
+				"cleaning up tx mapping vector element about to be replaced");
+		}
+		AST_VECTOR_REPLACE(&dest->payload_mapping_tx, idx, type);
+
+		if (instance && instance->engine && instance->engine->payload_set) {
+			instance->engine->payload_set(instance, idx, type->asterisk_format, type->format, type->rtp_code);
+		}
+
+		payload_mapping_tx_remove_other_mappings(dest, instance, type);
+	}
+}
 
-	ast_rwlock_rdlock(&src->codecs_lock);
+void ast_rtp_codecs_payloads_copy(struct ast_rtp_codecs *src, struct ast_rtp_codecs *dest, struct ast_rtp_instance *instance)
+{
 	ast_rwlock_wrlock(&dest->codecs_lock);
 
-	for (i = 0; i < AST_VECTOR_SIZE(&src->payloads); i++) {
-		struct ast_rtp_payload_type *type;
+	/* Deadlock avoidance because of held write lock. */
+	while (ast_rwlock_tryrdlock(&src->codecs_lock)) {
+		ast_rwlock_unlock(&dest->codecs_lock);
+		sched_yield();
+		ast_rwlock_wrlock(&dest->codecs_lock);
+	}
 
-		type = AST_VECTOR_GET(&src->payloads, i);
+	rtp_codecs_payloads_copy_rx(src, dest, instance);
+	rtp_codecs_payloads_copy_tx(src, dest, instance);
+	dest->framing = src->framing;
+
+	ast_rwlock_unlock(&src->codecs_lock);
+	ast_rwlock_unlock(&dest->codecs_lock);
+}
+
+void ast_rtp_codecs_payloads_xover(struct ast_rtp_codecs *src, struct ast_rtp_codecs *dest, struct ast_rtp_instance *instance)
+{
+	int idx;
+	struct ast_rtp_payload_type *type;
+
+	ast_rwlock_wrlock(&dest->codecs_lock);
+	if (src != dest) {
+		/* Deadlock avoidance because of held write lock. */
+		while (ast_rwlock_tryrdlock(&src->codecs_lock)) {
+			ast_rwlock_unlock(&dest->codecs_lock);
+			sched_yield();
+			ast_rwlock_wrlock(&dest->codecs_lock);
+		}
+	}
+
+	/* Crossover copy payload type tx mapping to rx mapping. */
+	for (idx = 0; idx < AST_VECTOR_SIZE(&src->payload_mapping_tx); ++idx) {
+		type = AST_VECTOR_GET(&src->payload_mapping_tx, idx);
 		if (!type) {
 			continue;
 		}
-		if (i < AST_VECTOR_SIZE(&dest->payloads)) {
-			ao2_t_cleanup(AST_VECTOR_GET(&dest->payloads, i), "cleaning up vector element about to be replaced");
+
+		/* All tx mapping elements should have the primary flag set. */
+		ast_assert(type->primary_mapping);
+
+		ast_debug(2, "Crossover copying tx to rx payload mapping %d (%p) from %p to %p\n",
+			idx, type, src, dest);
+		ao2_ref(type, +1);
+		if (idx < AST_VECTOR_SIZE(&dest->payload_mapping_rx)) {
+			ao2_t_cleanup(AST_VECTOR_GET(&dest->payload_mapping_rx, idx),
+				"cleaning up rx mapping vector element about to be replaced");
 		}
-		ast_debug(2, "Copying payload %d (%p) from %p to %p\n", i, type, src, dest);
-		ao2_bump(type);
-		AST_VECTOR_REPLACE(&dest->payloads, i, type);
+		AST_VECTOR_REPLACE(&dest->payload_mapping_rx, idx, type);
+
+		payload_mapping_rx_clear_primary(dest, type);
 
 		if (instance && instance->engine && instance->engine->payload_set) {
-			instance->engine->payload_set(instance, i, type->asterisk_format, type->format, type->rtp_code);
+			instance->engine->payload_set(instance, idx, type->asterisk_format, type->format, type->rtp_code);
 		}
 	}
+
 	dest->framing = src->framing;
+
+	if (src != dest) {
+		ast_rwlock_unlock(&src->codecs_lock);
+	}
 	ast_rwlock_unlock(&dest->codecs_lock);
-	ast_rwlock_unlock(&src->codecs_lock);
 }
 
 void ast_rtp_codecs_payloads_set_m_type(struct ast_rtp_codecs *codecs, struct ast_rtp_instance *instance, int payload)
@@ -665,15 +895,18 @@ void ast_rtp_codecs_payloads_set_m_type(struct ast_rtp_codecs *codecs, struct as
 
 	ast_rwlock_wrlock(&codecs->codecs_lock);
 
-	if (payload < AST_VECTOR_SIZE(&codecs->payloads)) {
-		ao2_t_cleanup(AST_VECTOR_GET(&codecs->payloads, payload), "cleaning up replaced payload type");
+	if (payload < AST_VECTOR_SIZE(&codecs->payload_mapping_tx)) {
+		ao2_t_cleanup(AST_VECTOR_GET(&codecs->payload_mapping_tx, payload),
+			"cleaning up replaced tx payload type");
 	}
-	AST_VECTOR_REPLACE(&codecs->payloads, payload, new_type);
+	AST_VECTOR_REPLACE(&codecs->payload_mapping_tx, payload, new_type);
 
 	if (instance && instance->engine && instance->engine->payload_set) {
 		instance->engine->payload_set(instance, payload, new_type->asterisk_format, new_type->format, new_type->rtp_code);
 	}
 
+	payload_mapping_tx_remove_other_mappings(codecs, instance, new_type);
+
 	ast_rwlock_unlock(&codecs->codecs_lock);
 }
 
@@ -682,7 +915,7 @@ int ast_rtp_codecs_payloads_set_rtpmap_type_rate(struct ast_rtp_codecs *codecs,
 				 enum ast_rtp_options options,
 				 unsigned int sample_rate)
 {
-	unsigned int i;
+	unsigned int idx;
 	int found = 0;
 
 	if (pt < 0 || pt >= AST_RTP_MAX_PT) {
@@ -691,8 +924,9 @@ int ast_rtp_codecs_payloads_set_rtpmap_type_rate(struct ast_rtp_codecs *codecs,
 
 	ast_rwlock_rdlock(&mime_types_lock);
 	ast_rwlock_wrlock(&codecs->codecs_lock);
-	for (i = 0; i < mime_types_len; ++i) {
-		const struct ast_rtp_mime_type *t = &ast_rtp_mime_types[i];
+
+	for (idx = 0; idx < mime_types_len; ++idx) {
+		const struct ast_rtp_mime_type *t = &ast_rtp_mime_types[idx];
 		struct ast_rtp_payload_type *new_type;
 
 		if (strcasecmp(mimesubtype, t->subtype)) {
@@ -718,27 +952,32 @@ int ast_rtp_codecs_payloads_set_rtpmap_type_rate(struct ast_rtp_codecs *codecs,
 			continue;
 		}
 
-		if (pt < AST_VECTOR_SIZE(&codecs->payloads)) {
-			ao2_t_cleanup(AST_VECTOR_GET(&codecs->payloads, pt), "cleaning up replaced payload type");
-		}
-
-		new_type->payload = pt;
 		new_type->asterisk_format = t->payload_type.asterisk_format;
 		new_type->rtp_code = t->payload_type.rtp_code;
-		if ((ast_format_cmp(t->payload_type.format, ast_format_g726) == AST_FORMAT_CMP_EQUAL) &&
-				t->payload_type.asterisk_format && (options & AST_RTP_OPT_G726_NONSTANDARD)) {
+		new_type->payload = pt;
+		new_type->primary_mapping = 1;
+		if (t->payload_type.asterisk_format
+			&& ast_format_cmp(t->payload_type.format, ast_format_g726) == AST_FORMAT_CMP_EQUAL
+			&& (options & AST_RTP_OPT_G726_NONSTANDARD)) {
 			new_type->format = ao2_bump(ast_format_g726_aal2);
 		} else {
 			new_type->format = ao2_bump(t->payload_type.format);
 		}
-		AST_VECTOR_REPLACE(&codecs->payloads, pt, new_type);
+
+		if (pt < AST_VECTOR_SIZE(&codecs->payload_mapping_tx)) {
+			ao2_t_cleanup(AST_VECTOR_GET(&codecs->payload_mapping_tx, pt),
+				"cleaning up replaced tx payload type");
+		}
+		AST_VECTOR_REPLACE(&codecs->payload_mapping_tx, pt, new_type);
 
 		if (instance && instance->engine && instance->engine->payload_set) {
 			instance->engine->payload_set(instance, pt, new_type->asterisk_format, new_type->format, new_type->rtp_code);
 		}
 
+		payload_mapping_tx_remove_other_mappings(codecs, instance, new_type);
 		break;
 	}
+
 	ast_rwlock_unlock(&codecs->codecs_lock);
 	ast_rwlock_unlock(&mime_types_lock);
 
@@ -761,10 +1000,11 @@ void ast_rtp_codecs_payloads_unset(struct ast_rtp_codecs *codecs, struct ast_rtp
 	ast_debug(2, "Unsetting payload %d on %p\n", payload, codecs);
 
 	ast_rwlock_wrlock(&codecs->codecs_lock);
-	if (payload < AST_VECTOR_SIZE(&codecs->payloads)) {
-		type = AST_VECTOR_GET(&codecs->payloads, payload);
+
+	if (payload < AST_VECTOR_SIZE(&codecs->payload_mapping_tx)) {
+		type = AST_VECTOR_GET(&codecs->payload_mapping_tx, payload);
 		ao2_cleanup(type);
-		AST_VECTOR_REPLACE(&codecs->payloads, payload, NULL);
+		AST_VECTOR_REPLACE(&codecs->payload_mapping_tx, payload, NULL);
 	}
 
 	if (instance && instance->engine && instance->engine->payload_set) {
@@ -783,8 +1023,8 @@ struct ast_rtp_payload_type *ast_rtp_codecs_get_payload(struct ast_rtp_codecs *c
 	}
 
 	ast_rwlock_rdlock(&codecs->codecs_lock);
-	if (payload < AST_VECTOR_SIZE(&codecs->payloads)) {
-		type = AST_VECTOR_GET(&codecs->payloads, payload);
+	if (payload < AST_VECTOR_SIZE(&codecs->payload_mapping_rx)) {
+		type = AST_VECTOR_GET(&codecs->payload_mapping_rx, payload);
 		ao2_bump(type);
 	}
 	ast_rwlock_unlock(&codecs->codecs_lock);
@@ -814,12 +1054,14 @@ int ast_rtp_codecs_payload_replace_format(struct ast_rtp_codecs *codecs, int pay
 	type->format = format;
 	type->asterisk_format = 1;
 	type->payload = payload;
+	type->primary_mapping = 1;
 
 	ast_rwlock_wrlock(&codecs->codecs_lock);
-	if (payload < AST_VECTOR_SIZE(&codecs->payloads)) {
-		ao2_cleanup(AST_VECTOR_GET(&codecs->payloads, payload));
+	if (payload < AST_VECTOR_SIZE(&codecs->payload_mapping_tx)) {
+		ao2_cleanup(AST_VECTOR_GET(&codecs->payload_mapping_tx, payload));
 	}
-	AST_VECTOR_REPLACE(&codecs->payloads, payload, type);
+	AST_VECTOR_REPLACE(&codecs->payload_mapping_tx, payload, type);
+	payload_mapping_tx_remove_other_mappings(codecs, NULL, type);
 	ast_rwlock_unlock(&codecs->codecs_lock);
 
 	return 0;
@@ -835,8 +1077,8 @@ struct ast_format *ast_rtp_codecs_get_payload_format(struct ast_rtp_codecs *code
 	}
 
 	ast_rwlock_rdlock(&codecs->codecs_lock);
-	if (payload < AST_VECTOR_SIZE(&codecs->payloads)) {
-		type = AST_VECTOR_GET(&codecs->payloads, payload);
+	if (payload < AST_VECTOR_SIZE(&codecs->payload_mapping_tx)) {
+		type = AST_VECTOR_GET(&codecs->payload_mapping_tx, payload);
 		if (type && type->asterisk_format) {
 			format = ao2_bump(type->format);
 		}
@@ -870,16 +1112,17 @@ unsigned int ast_rtp_codecs_get_framing(struct ast_rtp_codecs *codecs)
 
 void ast_rtp_codecs_payload_formats(struct ast_rtp_codecs *codecs, struct ast_format_cap *astformats, int *nonastformats)
 {
-	int i;
+	int idx;
 
 	ast_format_cap_remove_by_type(astformats, AST_MEDIA_TYPE_UNKNOWN);
 	*nonastformats = 0;
 
 	ast_rwlock_rdlock(&codecs->codecs_lock);
-	for (i = 0; i < AST_VECTOR_SIZE(&codecs->payloads); i++) {
+
+	for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_tx); ++idx) {
 		struct ast_rtp_payload_type *type;
 
-		type = AST_VECTOR_GET(&codecs->payloads, i);
+		type = AST_VECTOR_GET(&codecs->payload_mapping_tx, idx);
 		if (!type) {
 			continue;
 		}
@@ -890,7 +1133,6 @@ void ast_rtp_codecs_payload_formats(struct ast_rtp_codecs *codecs, struct ast_fo
 			*nonastformats |= type->rtp_code;
 		}
 	}
-
 	if (codecs->framing) {
 		ast_format_cap_set_framing(astformats, codecs->framing);
 	}
@@ -898,59 +1140,161 @@ void ast_rtp_codecs_payload_formats(struct ast_rtp_codecs *codecs, struct ast_fo
 	ast_rwlock_unlock(&codecs->codecs_lock);
 }
 
+/*!
+ * \internal
+ * \brief Find the static payload type mapping for the format.
+ * \since 14.0.0
+ *
+ * \param asterisk_format Non-zero if the given Asterisk format is present
+ * \param format Asterisk format to look for
+ * \param code The non-Asterisk format code to look for
+ *
+ * \retval Numerical payload type
+ * \retval -1 if not found.
+ */
+static int find_static_payload_type(int asterisk_format, const struct ast_format *format, int code)
+{
+	int idx;
+	int payload = -1;
+
+	if (!asterisk_format) {
+		ast_rwlock_rdlock(&static_RTP_PT_lock);
+		for (idx = 0; idx < AST_RTP_MAX_PT; ++idx) {
+			if (static_RTP_PT[idx]
+				&& !static_RTP_PT[idx]->asterisk_format
+				&& static_RTP_PT[idx]->rtp_code == code) {
+				payload = idx;
+				break;
+			}
+		}
+		ast_rwlock_unlock(&static_RTP_PT_lock);
+	} else if (format) {
+		ast_rwlock_rdlock(&static_RTP_PT_lock);
+		for (idx = 0; idx < AST_RTP_MAX_PT; ++idx) {
+			if (static_RTP_PT[idx]
+				&& static_RTP_PT[idx]->asterisk_format
+				&& ast_format_cmp(format, static_RTP_PT[idx]->format)
+					!= AST_FORMAT_CMP_NOT_EQUAL) {
+				payload = idx;
+				break;
+			}
+		}
+		ast_rwlock_unlock(&static_RTP_PT_lock);
+	}
+
+	return payload;
+}
+
 int ast_rtp_codecs_payload_code(struct ast_rtp_codecs *codecs, int asterisk_format, const struct ast_format *format, int code)
 {
 	struct ast_rtp_payload_type *type;
-	int i;
+	int idx;
 	int payload = -1;
 
-	ast_rwlock_rdlock(&codecs->codecs_lock);
-	for (i = 0; i < AST_VECTOR_SIZE(&codecs->payloads); i++) {
-		type = AST_VECTOR_GET(&codecs->payloads, i);
-		if (!type) {
-			continue;
+	if (!asterisk_format) {
+		ast_rwlock_rdlock(&codecs->codecs_lock);
+		for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_rx); ++idx) {
+			type = AST_VECTOR_GET(&codecs->payload_mapping_rx, idx);
+			if (!type) {
+				continue;
+			}
+
+			if (!type->asterisk_format
+				&& type->rtp_code == code) {
+				if (type->primary_mapping) {
+					payload = idx;
+					break;
+				}
+				if (payload == -1) {
+					payload = idx;
+				}
+			}
 		}
+		ast_rwlock_unlock(&codecs->codecs_lock);
+	} else if (format) {
+		ast_rwlock_rdlock(&codecs->codecs_lock);
+		for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_rx); ++idx) {
+			type = AST_VECTOR_GET(&codecs->payload_mapping_rx, idx);
+			if (!type) {
+				continue;
+			}
 
-		if ((asterisk_format && format && ast_format_cmp(format, type->format) == AST_FORMAT_CMP_EQUAL)
-			|| (!asterisk_format && type->rtp_code == code)) {
-			payload = i;
-			break;
+			if (type->asterisk_format
+				&& ast_format_cmp(format, type->format) == AST_FORMAT_CMP_EQUAL) {
+				if (type->primary_mapping) {
+					payload = idx;
+					break;
+				}
+				if (payload == -1) {
+					payload = idx;
+				}
+			}
 		}
+		ast_rwlock_unlock(&codecs->codecs_lock);
 	}
-	ast_rwlock_unlock(&codecs->codecs_lock);
 
 	if (payload < 0) {
-		ast_rwlock_rdlock(&static_RTP_PT_lock);
-		for (i = 0; i < AST_RTP_MAX_PT; i++) {
-			if (!static_RTP_PT[i]) {
+		payload = find_static_payload_type(asterisk_format, format, code);
+	}
+
+	return payload;
+}
+
+int ast_rtp_codecs_payload_code_tx(struct ast_rtp_codecs *codecs, int asterisk_format, const struct ast_format *format, int code)
+{
+	struct ast_rtp_payload_type *type;
+	int idx;
+	int payload = -1;
+
+	if (!asterisk_format) {
+		ast_rwlock_rdlock(&codecs->codecs_lock);
+		for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_tx); ++idx) {
+			type = AST_VECTOR_GET(&codecs->payload_mapping_tx, idx);
+			if (!type) {
 				continue;
 			}
-			if (static_RTP_PT[i]->asterisk_format && asterisk_format && format &&
-				(ast_format_cmp(format, static_RTP_PT[i]->format) != AST_FORMAT_CMP_NOT_EQUAL)) {
-				payload = i;
+
+			if (!type->asterisk_format
+				&& type->rtp_code == code) {
+				payload = idx;
 				break;
-			} else if (!static_RTP_PT[i]->asterisk_format && !asterisk_format &&
-				(static_RTP_PT[i]->rtp_code == code)) {
-				payload = i;
+			}
+		}
+		ast_rwlock_unlock(&codecs->codecs_lock);
+	} else if (format) {
+		ast_rwlock_rdlock(&codecs->codecs_lock);
+		for (idx = 0; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_tx); ++idx) {
+			type = AST_VECTOR_GET(&codecs->payload_mapping_tx, idx);
+			if (!type) {
+				continue;
+			}
+
+			if (type->asterisk_format
+				&& ast_format_cmp(format, type->format) == AST_FORMAT_CMP_EQUAL) {
+				payload = idx;
 				break;
 			}
 		}
-		ast_rwlock_unlock(&static_RTP_PT_lock);
+		ast_rwlock_unlock(&codecs->codecs_lock);
+	}
+
+	if (payload < 0) {
+		payload = find_static_payload_type(asterisk_format, format, code);
 	}
 
 	return payload;
 }
 
-int ast_rtp_codecs_find_payload_code(struct ast_rtp_codecs *codecs, int code)
+int ast_rtp_codecs_find_payload_code(struct ast_rtp_codecs *codecs, int payload)
 {
 	struct ast_rtp_payload_type *type;
 	int res = -1;
 
 	ast_rwlock_rdlock(&codecs->codecs_lock);
-	if (code < AST_VECTOR_SIZE(&codecs->payloads)) {
-		type = AST_VECTOR_GET(&codecs->payloads, code);
+	if (payload < AST_VECTOR_SIZE(&codecs->payload_mapping_tx)) {
+		type = AST_VECTOR_GET(&codecs->payload_mapping_tx, payload);
 		if (type) {
-			res = type->payload;
+			res = payload;
 		}
 	}
 	ast_rwlock_unlock(&codecs->codecs_lock);
@@ -1192,13 +1536,13 @@ void ast_rtp_instance_early_bridge_make_compatible(struct ast_channel *c_dst, st
 		goto done;
 	}
 
-	ast_rtp_codecs_payloads_copy(&instance_src->codecs, &instance_dst->codecs, instance_dst);
+	ast_rtp_codecs_payloads_xover(&instance_src->codecs, &instance_dst->codecs, instance_dst);
 
 	if (vinstance_dst && vinstance_src) {
-		ast_rtp_codecs_payloads_copy(&vinstance_src->codecs, &vinstance_dst->codecs, vinstance_dst);
+		ast_rtp_codecs_payloads_xover(&vinstance_src->codecs, &vinstance_dst->codecs, vinstance_dst);
 	}
 	if (tinstance_dst && tinstance_src) {
-		ast_rtp_codecs_payloads_copy(&tinstance_src->codecs, &tinstance_dst->codecs, tinstance_dst);
+		ast_rtp_codecs_payloads_xover(&tinstance_src->codecs, &tinstance_dst->codecs, tinstance_dst);
 	}
 
 	if (glue_dst->update_peer(c_dst, instance_src, vinstance_src, tinstance_src, cap_src, 0)) {
@@ -1772,6 +2116,7 @@ static void add_static_payload(int map, struct ast_format *format, int rtp_code)
 			type->rtp_code = rtp_code;
 		}
 		type->payload = map;
+		type->primary_mapping = 1;
 		ao2_cleanup(static_RTP_PT[map]);
 		static_RTP_PT[map] = type;
 	}