call/rtp_demuxer.cc - src/ - Git at Google

 /*
  *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "call/rtp_demuxer.h"

 #include "call/rtp_packet_sink_interface.h"
 #include "call/rtp_rtcp_demuxer_helper.h"
 #include "call/ssrc_binding_observer.h"
 #include "modules/rtp_rtcp/source/rtp_header_extensions.h"
 #include "modules/rtp_rtcp/source/rtp_packet_received.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/strings/string_builder.h"

 namespace webrtc {

 RtpDemuxerCriteria::RtpDemuxerCriteria() = default;
 RtpDemuxerCriteria::~RtpDemuxerCriteria() = default;

 // static
 std::string RtpDemuxer::DescribePacket(const RtpPacketReceived& packet) {
   rtc::StringBuilder sb;
   sb << "PT=" << packet.PayloadType() << " SSRC=" << packet.Ssrc();
   std::string mid;
   if (packet.GetExtension<RtpMid>(&mid)) {
     sb << " MID=" << mid;
   }
   std::string rsid;
   if (packet.GetExtension<RtpStreamId>(&rsid)) {
     sb << " RSID=" << rsid;
   }
   std::string rrsid;
   if (packet.GetExtension<RepairedRtpStreamId>(&rrsid)) {
     sb << " RRSID=" << rrsid;
   }
   return sb.Release();
 }

 RtpDemuxer::RtpDemuxer() = default;

 RtpDemuxer::~RtpDemuxer() {
   RTC_DCHECK(sink_by_mid_.empty());
   RTC_DCHECK(sink_by_ssrc_.empty());
   RTC_DCHECK(sinks_by_pt_.empty());
   RTC_DCHECK(sink_by_mid_and_rsid_.empty());
   RTC_DCHECK(sink_by_rsid_.empty());
   RTC_DCHECK(ssrc_binding_observers_.empty());
 }

 bool RtpDemuxer::AddSink(const RtpDemuxerCriteria& criteria,
                          RtpPacketSinkInterface* sink) {
   RTC_DCHECK(!criteria.payload_types.empty() || !criteria.ssrcs.empty() ||
              !criteria.mid.empty() || !criteria.rsid.empty());
   RTC_DCHECK(criteria.mid.empty() || IsLegalMidName(criteria.mid));
   RTC_DCHECK(criteria.rsid.empty() || IsLegalRsidName(criteria.rsid));
   RTC_DCHECK(sink);

   // We return false instead of DCHECKing for logical conflicts with the new
   // criteria because new sinks are created according to user-specified SDP and
   // we do not want to crash due to a data validation error.
   if (CriteriaWouldConflict(criteria)) {
     return false;
   }

   if (!criteria.mid.empty()) {
     if (criteria.rsid.empty()) {
       sink_by_mid_.emplace(criteria.mid, sink);
     } else {
       sink_by_mid_and_rsid_.emplace(std::make_pair(criteria.mid, criteria.rsid),
                                     sink);
     }
   } else {
     if (!criteria.rsid.empty()) {
       sink_by_rsid_.emplace(criteria.rsid, sink);
     }
   }

   for (uint32_t ssrc : criteria.ssrcs) {
     sink_by_ssrc_.emplace(ssrc, sink);
   }

   for (uint8_t payload_type : criteria.payload_types) {
     sinks_by_pt_.emplace(payload_type, sink);
   }

   RefreshKnownMids();

   return true;
 }

 bool RtpDemuxer::CriteriaWouldConflict(
     const RtpDemuxerCriteria& criteria) const {
   if (!criteria.mid.empty()) {
     if (criteria.rsid.empty()) {
       // If the MID is in the known_mids_ set, then there is already a sink
       // added for this MID directly, or there is a sink already added with a
       // MID, RSID pair for our MID and some RSID.
       // Adding this criteria would cause one of these rules to be shadowed, so
       // reject this new criteria.
       if (known_mids_.find(criteria.mid) != known_mids_.end()) {
         return true;
       }
     } else {
       // If the exact rule already exists, then reject this duplicate.
       if (sink_by_mid_and_rsid_.find(std::make_pair(
               criteria.mid, criteria.rsid)) != sink_by_mid_and_rsid_.end()) {
         return true;
       }
       // If there is already a sink registered for the bare MID, then this
       // criteria will never receive any packets because they will just be
       // directed to that MID sink, so reject this new criteria.
       if (sink_by_mid_.find(criteria.mid) != sink_by_mid_.end()) {
         return true;
       }
     }
   }

   for (uint32_t ssrc : criteria.ssrcs) {
     if (sink_by_ssrc_.find(ssrc) != sink_by_ssrc_.end()) {
       return true;
     }
   }

   // TODO(steveanton): May also sanity check payload types.

   return false;
 }

 void RtpDemuxer::RefreshKnownMids() {
   known_mids_.clear();

   for (auto const& item : sink_by_mid_) {
     const std::string& mid = item.first;
     known_mids_.insert(mid);
   }

   for (auto const& item : sink_by_mid_and_rsid_) {
     const std::string& mid = item.first.first;
     known_mids_.insert(mid);
   }
 }

 bool RtpDemuxer::AddSink(uint32_t ssrc, RtpPacketSinkInterface* sink) {
   RtpDemuxerCriteria criteria;
   criteria.ssrcs.insert(ssrc);
   return AddSink(criteria, sink);
 }

 void RtpDemuxer::AddSink(const std::string& rsid,
                          RtpPacketSinkInterface* sink) {
   RtpDemuxerCriteria criteria;
   criteria.rsid = rsid;
   AddSink(criteria, sink);
 }

 bool RtpDemuxer::RemoveSink(const RtpPacketSinkInterface* sink) {
   RTC_DCHECK(sink);
   size_t num_removed = RemoveFromMapByValue(&sink_by_mid_, sink) +
                        RemoveFromMapByValue(&sink_by_ssrc_, sink) +
                        RemoveFromMultimapByValue(&sinks_by_pt_, sink) +
                        RemoveFromMapByValue(&sink_by_mid_and_rsid_, sink) +
                        RemoveFromMapByValue(&sink_by_rsid_, sink);
   RefreshKnownMids();
   return num_removed > 0;
 }

 bool RtpDemuxer::OnRtpPacket(const RtpPacketReceived& packet) {
   RtpPacketSinkInterface* sink = ResolveSink(packet);
   if (sink != nullptr) {
     sink->OnRtpPacket(packet);
     return true;
   }
   return false;
 }

 RtpPacketSinkInterface* RtpDemuxer::ResolveSink(
     const RtpPacketReceived& packet) {
   // See the BUNDLE spec for high level reference to this algorithm:
   // https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-38#section-10.2

   // RSID and RRID are routed to the same sinks. If an RSID is specified on a
   // repair packet, it should be ignored and the RRID should be used.
   std::string packet_mid, packet_rsid;
   bool has_mid = use_mid_ && packet.GetExtension<RtpMid>(&packet_mid);
   bool has_rsid = packet.GetExtension<RepairedRtpStreamId>(&packet_rsid);
   if (!has_rsid) {
     has_rsid = packet.GetExtension<RtpStreamId>(&packet_rsid);
   }
   uint32_t ssrc = packet.Ssrc();

   // The BUNDLE spec says to drop any packets with unknown MIDs, even if the
   // SSRC is known/latched.
   if (has_mid && known_mids_.find(packet_mid) == known_mids_.end()) {
     return nullptr;
   }

   // Cache information we learn about SSRCs and IDs. We need to do this even if
   // there isn't a rule/sink yet because we might add an MID/RSID rule after
   // learning an MID/RSID<->SSRC association.

   std::string* mid = nullptr;
   if (has_mid) {
     mid_by_ssrc_[ssrc] = packet_mid;
     mid = &packet_mid;
   } else {
     // If the packet does not include a MID header extension, check if there is
     // a latched MID for the SSRC.
     const auto it = mid_by_ssrc_.find(ssrc);
     if (it != mid_by_ssrc_.end()) {
       mid = &it->second;
     }
   }

   std::string* rsid = nullptr;
   if (has_rsid) {
     rsid_by_ssrc_[ssrc] = packet_rsid;
     rsid = &packet_rsid;
   } else {
     // If the packet does not include an RRID/RSID header extension, check if
     // there is a latched RSID for the SSRC.
     const auto it = rsid_by_ssrc_.find(ssrc);
     if (it != rsid_by_ssrc_.end()) {
       rsid = &it->second;
     }
   }

   // If MID and/or RSID is specified, prioritize that for demuxing the packet.
   // The motivation behind the BUNDLE algorithm is that we trust these are used
   // deliberately by senders and are more likely to be correct than SSRC/payload
   // type which are included with every packet.
   // TODO(steveanton): According to the BUNDLE spec, new SSRC mappings are only
   //                   accepted if the packet's extended sequence number is
   //                   greater than that of the last SSRC mapping update.
   //                   https://tools.ietf.org/html/rfc7941#section-4.2.6
   if (mid != nullptr) {
     RtpPacketSinkInterface* sink_by_mid = ResolveSinkByMid(*mid, ssrc);
     if (sink_by_mid != nullptr) {
       return sink_by_mid;
     }

     // RSID is scoped to a given MID if both are included.
     if (rsid != nullptr) {
       RtpPacketSinkInterface* sink_by_mid_rsid =
           ResolveSinkByMidRsid(*mid, *rsid, ssrc);
       if (sink_by_mid_rsid != nullptr) {
         return sink_by_mid_rsid;
       }
     }

     // At this point, there is at least one sink added for this MID and an RSID
     // but either the packet does not have an RSID or it is for a different
     // RSID. This falls outside the BUNDLE spec so drop the packet.
     return nullptr;
   }

   // RSID can be used without MID as long as they are unique.
   if (rsid != nullptr) {
     RtpPacketSinkInterface* sink_by_rsid = ResolveSinkByRsid(*rsid, ssrc);
     if (sink_by_rsid != nullptr) {
       return sink_by_rsid;
     }
   }

   // We trust signaled SSRC more than payload type which is likely to conflict
   // between streams.
   const auto ssrc_sink_it = sink_by_ssrc_.find(ssrc);
   if (ssrc_sink_it != sink_by_ssrc_.end()) {
     return ssrc_sink_it->second;
   }

   // Legacy senders will only signal payload type, support that as last resort.
   return ResolveSinkByPayloadType(packet.PayloadType(), ssrc);
 }

 RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByMid(const std::string& mid,
                                                      uint32_t ssrc) {
   const auto it = sink_by_mid_.find(mid);
   if (it != sink_by_mid_.end()) {
     RtpPacketSinkInterface* sink = it->second;
     bool notify = AddSsrcSinkBinding(ssrc, sink);
     if (notify) {
       for (auto* observer : ssrc_binding_observers_) {
         observer->OnSsrcBoundToMid(mid, ssrc);
       }
     }
     return sink;
   }
   return nullptr;
 }

 RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByMidRsid(
     const std::string& mid,
     const std::string& rsid,
     uint32_t ssrc) {
   const auto it = sink_by_mid_and_rsid_.find(std::make_pair(mid, rsid));
   if (it != sink_by_mid_and_rsid_.end()) {
     RtpPacketSinkInterface* sink = it->second;
     bool notify = AddSsrcSinkBinding(ssrc, sink);
     if (notify) {
       for (auto* observer : ssrc_binding_observers_) {
         observer->OnSsrcBoundToMidRsid(mid, rsid, ssrc);
       }
     }
     return sink;
   }
   return nullptr;
 }
 void RtpDemuxer::RegisterRsidResolutionObserver(SsrcBindingObserver* observer) {
   RegisterSsrcBindingObserver(observer);
 }

 RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByRsid(const std::string& rsid,
                                                       uint32_t ssrc) {
   const auto it = sink_by_rsid_.find(rsid);
   if (it != sink_by_rsid_.end()) {
     RtpPacketSinkInterface* sink = it->second;
     bool notify = AddSsrcSinkBinding(ssrc, sink);
     if (notify) {
       for (auto* observer : ssrc_binding_observers_) {
         observer->OnSsrcBoundToRsid(rsid, ssrc);
       }
     }
     return sink;
   }
   return nullptr;
 }
 void RtpDemuxer::DeregisterRsidResolutionObserver(
     const SsrcBindingObserver* observer) {
   DeregisterSsrcBindingObserver(observer);
 }

 RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByPayloadType(
     uint8_t payload_type,
     uint32_t ssrc) {
   const auto range = sinks_by_pt_.equal_range(payload_type);
   if (range.first != range.second) {
     auto it = range.first;
     const auto end = range.second;
     if (std::next(it) == end) {
       RtpPacketSinkInterface* sink = it->second;
       bool notify = AddSsrcSinkBinding(ssrc, sink);
       if (notify) {
         for (auto* observer : ssrc_binding_observers_) {
           observer->OnSsrcBoundToPayloadType(payload_type, ssrc);
         }
       }
       return sink;
     }
   }
   return nullptr;
 }

 bool RtpDemuxer::AddSsrcSinkBinding(uint32_t ssrc,
                                     RtpPacketSinkInterface* sink) {
   if (sink_by_ssrc_.size() >= kMaxSsrcBindings) {
     RTC_LOG(LS_WARNING) << "New SSRC=" << ssrc
                         << " sink binding ignored; limit of" << kMaxSsrcBindings
                         << " bindings has been reached.";
     return false;
   }

   auto result = sink_by_ssrc_.emplace(ssrc, sink);
   auto it = result.first;
   bool inserted = result.second;
   if (inserted) {
     return true;
   }
   if (it->second != sink) {
     it->second = sink;
     return true;
   }
   return false;
 }

 void RtpDemuxer::RegisterSsrcBindingObserver(SsrcBindingObserver* observer) {
   RTC_DCHECK(observer);
   RTC_DCHECK(!ContainerHasKey(ssrc_binding_observers_, observer));

   ssrc_binding_observers_.push_back(observer);
 }

 void RtpDemuxer::DeregisterSsrcBindingObserver(
     const SsrcBindingObserver* observer) {
   RTC_DCHECK(observer);
   auto it = std::find(ssrc_binding_observers_.begin(),
                       ssrc_binding_observers_.end(), observer);
   RTC_DCHECK(it != ssrc_binding_observers_.end());
   ssrc_binding_observers_.erase(it);
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "call/rtp_demuxer.h"

	#include "call/rtp_packet_sink_interface.h"
	#include "call/rtp_rtcp_demuxer_helper.h"
	#include "call/ssrc_binding_observer.h"
	#include "modules/rtp_rtcp/source/rtp_header_extensions.h"
	#include "modules/rtp_rtcp/source/rtp_packet_received.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/strings/string_builder.h"

	namespace webrtc {

	RtpDemuxerCriteria::RtpDemuxerCriteria() = default;
	RtpDemuxerCriteria::~RtpDemuxerCriteria() = default;

	// static
	std::string RtpDemuxer::DescribePacket(const RtpPacketReceived& packet) {
	rtc::StringBuilder sb;
	sb << "PT=" << packet.PayloadType() << " SSRC=" << packet.Ssrc();
	std::string mid;
	if (packet.GetExtension<RtpMid>(&mid)) {
	sb << " MID=" << mid;
	}
	std::string rsid;
	if (packet.GetExtension<RtpStreamId>(&rsid)) {
	sb << " RSID=" << rsid;
	}
	std::string rrsid;
	if (packet.GetExtension<RepairedRtpStreamId>(&rrsid)) {
	sb << " RRSID=" << rrsid;
	}
	return sb.Release();
	}

	RtpDemuxer::RtpDemuxer() = default;

	RtpDemuxer::~RtpDemuxer() {
	RTC_DCHECK(sink_by_mid_.empty());
	RTC_DCHECK(sink_by_ssrc_.empty());
	RTC_DCHECK(sinks_by_pt_.empty());
	RTC_DCHECK(sink_by_mid_and_rsid_.empty());
	RTC_DCHECK(sink_by_rsid_.empty());
	RTC_DCHECK(ssrc_binding_observers_.empty());
	}

	bool RtpDemuxer::AddSink(const RtpDemuxerCriteria& criteria,
	RtpPacketSinkInterface* sink) {
	RTC_DCHECK(!criteria.payload_types.empty() \|\| !criteria.ssrcs.empty() \|\|
	!criteria.mid.empty() \|\| !criteria.rsid.empty());
	RTC_DCHECK(criteria.mid.empty() \|\| IsLegalMidName(criteria.mid));
	RTC_DCHECK(criteria.rsid.empty() \|\| IsLegalRsidName(criteria.rsid));
	RTC_DCHECK(sink);

	// We return false instead of DCHECKing for logical conflicts with the new
	// criteria because new sinks are created according to user-specified SDP and
	// we do not want to crash due to a data validation error.
	if (CriteriaWouldConflict(criteria)) {
	return false;
	}

	if (!criteria.mid.empty()) {
	if (criteria.rsid.empty()) {
	sink_by_mid_.emplace(criteria.mid, sink);
	} else {
	sink_by_mid_and_rsid_.emplace(std::make_pair(criteria.mid, criteria.rsid),
	sink);
	}
	} else {
	if (!criteria.rsid.empty()) {
	sink_by_rsid_.emplace(criteria.rsid, sink);
	}
	}

	for (uint32_t ssrc : criteria.ssrcs) {
	sink_by_ssrc_.emplace(ssrc, sink);
	}

	for (uint8_t payload_type : criteria.payload_types) {
	sinks_by_pt_.emplace(payload_type, sink);
	}

	RefreshKnownMids();

	return true;
	}

	bool RtpDemuxer::CriteriaWouldConflict(
	const RtpDemuxerCriteria& criteria) const {
	if (!criteria.mid.empty()) {
	if (criteria.rsid.empty()) {
	// If the MID is in the known_mids_ set, then there is already a sink
	// added for this MID directly, or there is a sink already added with a
	// MID, RSID pair for our MID and some RSID.
	// Adding this criteria would cause one of these rules to be shadowed, so
	// reject this new criteria.
	if (known_mids_.find(criteria.mid) != known_mids_.end()) {
	return true;
	}
	} else {
	// If the exact rule already exists, then reject this duplicate.
	if (sink_by_mid_and_rsid_.find(std::make_pair(
	criteria.mid, criteria.rsid)) != sink_by_mid_and_rsid_.end()) {
	return true;
	}
	// If there is already a sink registered for the bare MID, then this
	// criteria will never receive any packets because they will just be
	// directed to that MID sink, so reject this new criteria.
	if (sink_by_mid_.find(criteria.mid) != sink_by_mid_.end()) {
	return true;
	}
	}
	}

	for (uint32_t ssrc : criteria.ssrcs) {
	if (sink_by_ssrc_.find(ssrc) != sink_by_ssrc_.end()) {
	return true;
	}
	}

	// TODO(steveanton): May also sanity check payload types.

	return false;
	}

	void RtpDemuxer::RefreshKnownMids() {
	known_mids_.clear();

	for (auto const& item : sink_by_mid_) {
	const std::string& mid = item.first;
	known_mids_.insert(mid);
	}

	for (auto const& item : sink_by_mid_and_rsid_) {
	const std::string& mid = item.first.first;
	known_mids_.insert(mid);
	}
	}

	bool RtpDemuxer::AddSink(uint32_t ssrc, RtpPacketSinkInterface* sink) {
	RtpDemuxerCriteria criteria;
	criteria.ssrcs.insert(ssrc);
	return AddSink(criteria, sink);
	}

	void RtpDemuxer::AddSink(const std::string& rsid,
	RtpPacketSinkInterface* sink) {
	RtpDemuxerCriteria criteria;
	criteria.rsid = rsid;
	AddSink(criteria, sink);
	}

	bool RtpDemuxer::RemoveSink(const RtpPacketSinkInterface* sink) {
	RTC_DCHECK(sink);
	size_t num_removed = RemoveFromMapByValue(&sink_by_mid_, sink) +
	RemoveFromMapByValue(&sink_by_ssrc_, sink) +
	RemoveFromMultimapByValue(&sinks_by_pt_, sink) +
	RemoveFromMapByValue(&sink_by_mid_and_rsid_, sink) +
	RemoveFromMapByValue(&sink_by_rsid_, sink);
	RefreshKnownMids();
	return num_removed > 0;
	}

	bool RtpDemuxer::OnRtpPacket(const RtpPacketReceived& packet) {
	RtpPacketSinkInterface* sink = ResolveSink(packet);
	if (sink != nullptr) {
	sink->OnRtpPacket(packet);
	return true;
	}
	return false;
	}

	RtpPacketSinkInterface* RtpDemuxer::ResolveSink(
	const RtpPacketReceived& packet) {
	// See the BUNDLE spec for high level reference to this algorithm:
	// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-38#section-10.2

	// RSID and RRID are routed to the same sinks. If an RSID is specified on a
	// repair packet, it should be ignored and the RRID should be used.
	std::string packet_mid, packet_rsid;
	bool has_mid = use_mid_ && packet.GetExtension<RtpMid>(&packet_mid);
	bool has_rsid = packet.GetExtension<RepairedRtpStreamId>(&packet_rsid);
	if (!has_rsid) {
	has_rsid = packet.GetExtension<RtpStreamId>(&packet_rsid);
	}
	uint32_t ssrc = packet.Ssrc();

	// The BUNDLE spec says to drop any packets with unknown MIDs, even if the
	// SSRC is known/latched.
	if (has_mid && known_mids_.find(packet_mid) == known_mids_.end()) {
	return nullptr;
	}

	// Cache information we learn about SSRCs and IDs. We need to do this even if
	// there isn't a rule/sink yet because we might add an MID/RSID rule after
	// learning an MID/RSID<->SSRC association.

	std::string* mid = nullptr;
	if (has_mid) {
	mid_by_ssrc_[ssrc] = packet_mid;
	mid = &packet_mid;
	} else {
	// If the packet does not include a MID header extension, check if there is
	// a latched MID for the SSRC.
	const auto it = mid_by_ssrc_.find(ssrc);
	if (it != mid_by_ssrc_.end()) {
	mid = &it->second;
	}
	}

	std::string* rsid = nullptr;
	if (has_rsid) {
	rsid_by_ssrc_[ssrc] = packet_rsid;
	rsid = &packet_rsid;
	} else {
	// If the packet does not include an RRID/RSID header extension, check if
	// there is a latched RSID for the SSRC.
	const auto it = rsid_by_ssrc_.find(ssrc);
	if (it != rsid_by_ssrc_.end()) {
	rsid = &it->second;
	}
	}

	// If MID and/or RSID is specified, prioritize that for demuxing the packet.
	// The motivation behind the BUNDLE algorithm is that we trust these are used
	// deliberately by senders and are more likely to be correct than SSRC/payload
	// type which are included with every packet.
	// TODO(steveanton): According to the BUNDLE spec, new SSRC mappings are only
	// accepted if the packet's extended sequence number is
	// greater than that of the last SSRC mapping update.
	// https://tools.ietf.org/html/rfc7941#section-4.2.6
	if (mid != nullptr) {
	RtpPacketSinkInterface* sink_by_mid = ResolveSinkByMid(*mid, ssrc);
	if (sink_by_mid != nullptr) {
	return sink_by_mid;
	}

	// RSID is scoped to a given MID if both are included.
	if (rsid != nullptr) {
	RtpPacketSinkInterface* sink_by_mid_rsid =
	ResolveSinkByMidRsid(mid, rsid, ssrc);
	if (sink_by_mid_rsid != nullptr) {
	return sink_by_mid_rsid;
	}
	}

	// At this point, there is at least one sink added for this MID and an RSID
	// but either the packet does not have an RSID or it is for a different
	// RSID. This falls outside the BUNDLE spec so drop the packet.
	return nullptr;
	}

	// RSID can be used without MID as long as they are unique.
	if (rsid != nullptr) {
	RtpPacketSinkInterface* sink_by_rsid = ResolveSinkByRsid(*rsid, ssrc);
	if (sink_by_rsid != nullptr) {
	return sink_by_rsid;
	}
	}

	// We trust signaled SSRC more than payload type which is likely to conflict
	// between streams.
	const auto ssrc_sink_it = sink_by_ssrc_.find(ssrc);
	if (ssrc_sink_it != sink_by_ssrc_.end()) {
	return ssrc_sink_it->second;
	}

	// Legacy senders will only signal payload type, support that as last resort.
	return ResolveSinkByPayloadType(packet.PayloadType(), ssrc);
	}

	RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByMid(const std::string& mid,
	uint32_t ssrc) {
	const auto it = sink_by_mid_.find(mid);
	if (it != sink_by_mid_.end()) {
	RtpPacketSinkInterface* sink = it->second;
	bool notify = AddSsrcSinkBinding(ssrc, sink);
	if (notify) {
	for (auto* observer : ssrc_binding_observers_) {
	observer->OnSsrcBoundToMid(mid, ssrc);
	}
	}
	return sink;
	}
	return nullptr;
	}

	RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByMidRsid(
	const std::string& mid,
	const std::string& rsid,
	uint32_t ssrc) {
	const auto it = sink_by_mid_and_rsid_.find(std::make_pair(mid, rsid));
	if (it != sink_by_mid_and_rsid_.end()) {
	RtpPacketSinkInterface* sink = it->second;
	bool notify = AddSsrcSinkBinding(ssrc, sink);
	if (notify) {
	for (auto* observer : ssrc_binding_observers_) {
	observer->OnSsrcBoundToMidRsid(mid, rsid, ssrc);
	}
	}
	return sink;
	}
	return nullptr;
	}
	void RtpDemuxer::RegisterRsidResolutionObserver(SsrcBindingObserver* observer) {
	RegisterSsrcBindingObserver(observer);
	}

	RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByRsid(const std::string& rsid,
	uint32_t ssrc) {
	const auto it = sink_by_rsid_.find(rsid);
	if (it != sink_by_rsid_.end()) {
	RtpPacketSinkInterface* sink = it->second;
	bool notify = AddSsrcSinkBinding(ssrc, sink);
	if (notify) {
	for (auto* observer : ssrc_binding_observers_) {
	observer->OnSsrcBoundToRsid(rsid, ssrc);
	}
	}
	return sink;
	}
	return nullptr;
	}
	void RtpDemuxer::DeregisterRsidResolutionObserver(
	const SsrcBindingObserver* observer) {
	DeregisterSsrcBindingObserver(observer);
	}

	RtpPacketSinkInterface* RtpDemuxer::ResolveSinkByPayloadType(
	uint8_t payload_type,
	uint32_t ssrc) {
	const auto range = sinks_by_pt_.equal_range(payload_type);
	if (range.first != range.second) {
	auto it = range.first;
	const auto end = range.second;
	if (std::next(it) == end) {
	RtpPacketSinkInterface* sink = it->second;
	bool notify = AddSsrcSinkBinding(ssrc, sink);
	if (notify) {
	for (auto* observer : ssrc_binding_observers_) {
	observer->OnSsrcBoundToPayloadType(payload_type, ssrc);
	}
	}
	return sink;
	}
	}
	return nullptr;
	}

	bool RtpDemuxer::AddSsrcSinkBinding(uint32_t ssrc,
	RtpPacketSinkInterface* sink) {
	if (sink_by_ssrc_.size() >= kMaxSsrcBindings) {
	RTC_LOG(LS_WARNING) << "New SSRC=" << ssrc
	<< " sink binding ignored; limit of" << kMaxSsrcBindings
	<< " bindings has been reached.";
	return false;
	}

	auto result = sink_by_ssrc_.emplace(ssrc, sink);
	auto it = result.first;
	bool inserted = result.second;
	if (inserted) {
	return true;
	}
	if (it->second != sink) {
	it->second = sink;
	return true;
	}
	return false;
	}

	void RtpDemuxer::RegisterSsrcBindingObserver(SsrcBindingObserver* observer) {
	RTC_DCHECK(observer);
	RTC_DCHECK(!ContainerHasKey(ssrc_binding_observers_, observer));

	ssrc_binding_observers_.push_back(observer);
	}

	void RtpDemuxer::DeregisterSsrcBindingObserver(
	const SsrcBindingObserver* observer) {
	RTC_DCHECK(observer);
	auto it = std::find(ssrc_binding_observers_.begin(),
	ssrc_binding_observers_.end(), observer);
	RTC_DCHECK(it != ssrc_binding_observers_.end());
	ssrc_binding_observers_.erase(it);
	}

	} // namespace webrtc