Repo created

TMessagesProj/jni/voip/webrtc/pc/rtp_transmission_manager.cc

@@ -0,0 +1,730 @@
+/*
+ *  Copyright 2020 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 "pc/rtp_transmission_manager.h"
+
+#include <type_traits>
+#include <utility>
+
+#include "absl/types/optional.h"
+#include "api/peer_connection_interface.h"
+#include "api/rtp_transceiver_direction.h"
+#include "pc/audio_rtp_receiver.h"
+#include "pc/channel_interface.h"
+#include "pc/legacy_stats_collector_interface.h"
+#include "pc/video_rtp_receiver.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+namespace {
+
+static const char kDefaultAudioSenderId[] = "defaulta0";
+static const char kDefaultVideoSenderId[] = "defaultv0";
+
+}  // namespace
+
+RtpTransmissionManager::RtpTransmissionManager(
+    bool is_unified_plan,
+    ConnectionContext* context,
+    UsagePattern* usage_pattern,
+    PeerConnectionObserver* observer,
+    LegacyStatsCollectorInterface* legacy_stats,
+    std::function<void()> on_negotiation_needed)
+    : is_unified_plan_(is_unified_plan),
+      context_(context),
+      usage_pattern_(usage_pattern),
+      observer_(observer),
+      legacy_stats_(legacy_stats),
+      on_negotiation_needed_(on_negotiation_needed),
+      weak_ptr_factory_(this) {}
+
+void RtpTransmissionManager::Close() {
+  closed_ = true;
+  observer_ = nullptr;
+}
+
+// Implementation of SetStreamsObserver
+void RtpTransmissionManager::OnSetStreams() {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  if (IsUnifiedPlan())
+    OnNegotiationNeeded();
+}
+
+// Function to call back to the PeerConnection when negotiation is needed
+void RtpTransmissionManager::OnNegotiationNeeded() {
+  on_negotiation_needed_();
+}
+
+// Function that returns the currently valid observer
+PeerConnectionObserver* RtpTransmissionManager::Observer() const {
+  RTC_DCHECK(!closed_);
+  RTC_DCHECK(observer_);
+  return observer_;
+}
+
+cricket::VoiceMediaSendChannelInterface*
+RtpTransmissionManager::voice_media_send_channel() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto* voice_channel = GetAudioTransceiver()->internal()->channel();
+  if (voice_channel) {
+    return voice_channel->voice_media_send_channel();
+  } else {
+    return nullptr;
+  }
+}
+
+cricket::VideoMediaSendChannelInterface*
+RtpTransmissionManager::video_media_send_channel() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto* video_channel = GetVideoTransceiver()->internal()->channel();
+  if (video_channel) {
+    return video_channel->video_media_send_channel();
+  } else {
+    return nullptr;
+  }
+}
+cricket::VoiceMediaReceiveChannelInterface*
+RtpTransmissionManager::voice_media_receive_channel() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto* voice_channel = GetAudioTransceiver()->internal()->channel();
+  if (voice_channel) {
+    return voice_channel->voice_media_receive_channel();
+  } else {
+    return nullptr;
+  }
+}
+
+cricket::VideoMediaReceiveChannelInterface*
+RtpTransmissionManager::video_media_receive_channel() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto* video_channel = GetVideoTransceiver()->internal()->channel();
+  if (video_channel) {
+    return video_channel->video_media_receive_channel();
+  } else {
+    return nullptr;
+  }
+}
+
+RTCErrorOr<rtc::scoped_refptr<RtpSenderInterface>>
+RtpTransmissionManager::AddTrack(
+    rtc::scoped_refptr<MediaStreamTrackInterface> track,
+    const std::vector<std::string>& stream_ids,
+    const std::vector<RtpEncodingParameters>* init_send_encodings) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+
+  return (IsUnifiedPlan()
+              ? AddTrackUnifiedPlan(track, stream_ids, init_send_encodings)
+              : AddTrackPlanB(track, stream_ids, init_send_encodings));
+}
+
+RTCErrorOr<rtc::scoped_refptr<RtpSenderInterface>>
+RtpTransmissionManager::AddTrackPlanB(
+    rtc::scoped_refptr<MediaStreamTrackInterface> track,
+    const std::vector<std::string>& stream_ids,
+    const std::vector<RtpEncodingParameters>* init_send_encodings) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  if (stream_ids.size() > 1u) {
+    LOG_AND_RETURN_ERROR(RTCErrorType::UNSUPPORTED_OPERATION,
+                         "AddTrack with more than one stream is not "
+                         "supported with Plan B semantics.");
+  }
+  std::vector<std::string> adjusted_stream_ids = stream_ids;
+  if (adjusted_stream_ids.empty()) {
+    adjusted_stream_ids.push_back(rtc::CreateRandomUuid());
+  }
+  cricket::MediaType media_type =
+      (track->kind() == MediaStreamTrackInterface::kAudioKind
+           ? cricket::MEDIA_TYPE_AUDIO
+           : cricket::MEDIA_TYPE_VIDEO);
+  auto new_sender = CreateSender(
+      media_type, track->id(), track, adjusted_stream_ids,
+      init_send_encodings
+          ? *init_send_encodings
+          : std::vector<RtpEncodingParameters>(1, RtpEncodingParameters{}));
+  if (track->kind() == MediaStreamTrackInterface::kAudioKind) {
+    new_sender->internal()->SetMediaChannel(voice_media_send_channel());
+    GetAudioTransceiver()->internal()->AddSender(new_sender);
+    const RtpSenderInfo* sender_info =
+        FindSenderInfo(local_audio_sender_infos_,
+                       new_sender->internal()->stream_ids()[0], track->id());
+    if (sender_info) {
+      new_sender->internal()->SetSsrc(sender_info->first_ssrc);
+    }
+  } else {
+    RTC_DCHECK_EQ(MediaStreamTrackInterface::kVideoKind, track->kind());
+    new_sender->internal()->SetMediaChannel(video_media_send_channel());
+    GetVideoTransceiver()->internal()->AddSender(new_sender);
+    const RtpSenderInfo* sender_info =
+        FindSenderInfo(local_video_sender_infos_,
+                       new_sender->internal()->stream_ids()[0], track->id());
+    if (sender_info) {
+      new_sender->internal()->SetSsrc(sender_info->first_ssrc);
+    }
+  }
+  return rtc::scoped_refptr<RtpSenderInterface>(new_sender);
+}
+
+RTCErrorOr<rtc::scoped_refptr<RtpSenderInterface>>
+RtpTransmissionManager::AddTrackUnifiedPlan(
+    rtc::scoped_refptr<MediaStreamTrackInterface> track,
+    const std::vector<std::string>& stream_ids,
+    const std::vector<RtpEncodingParameters>* init_send_encodings) {
+  auto transceiver =
+      FindFirstTransceiverForAddedTrack(track, init_send_encodings);
+  if (transceiver) {
+    RTC_LOG(LS_INFO) << "Reusing an existing "
+                     << cricket::MediaTypeToString(transceiver->media_type())
+                     << " transceiver for AddTrack.";
+    if (transceiver->stopping()) {
+      LOG_AND_RETURN_ERROR(RTCErrorType::INVALID_PARAMETER,
+                           "The existing transceiver is stopping.");
+    }
+
+    if (transceiver->direction() == RtpTransceiverDirection::kRecvOnly) {
+      transceiver->internal()->set_direction(
+          RtpTransceiverDirection::kSendRecv);
+    } else if (transceiver->direction() == RtpTransceiverDirection::kInactive) {
+      transceiver->internal()->set_direction(
+          RtpTransceiverDirection::kSendOnly);
+    }
+    transceiver->sender()->SetTrack(track.get());
+    transceiver->internal()->sender_internal()->set_stream_ids(stream_ids);
+    transceiver->internal()->set_reused_for_addtrack(true);
+  } else {
+    cricket::MediaType media_type =
+        (track->kind() == MediaStreamTrackInterface::kAudioKind
+             ? cricket::MEDIA_TYPE_AUDIO
+             : cricket::MEDIA_TYPE_VIDEO);
+    RTC_LOG(LS_INFO) << "Adding " << cricket::MediaTypeToString(media_type)
+                     << " transceiver in response to a call to AddTrack.";
+    std::string sender_id = track->id();
+    // Avoid creating a sender with an existing ID by generating a random ID.
+    // This can happen if this is the second time AddTrack has created a sender
+    // for this track.
+    if (FindSenderById(sender_id)) {
+      sender_id = rtc::CreateRandomUuid();
+    }
+    auto sender = CreateSender(
+        media_type, sender_id, track, stream_ids,
+        init_send_encodings
+            ? *init_send_encodings
+            : std::vector<RtpEncodingParameters>(1, RtpEncodingParameters{}));
+    auto receiver = CreateReceiver(media_type, rtc::CreateRandomUuid());
+    transceiver = CreateAndAddTransceiver(sender, receiver);
+    transceiver->internal()->set_created_by_addtrack(true);
+    transceiver->internal()->set_direction(RtpTransceiverDirection::kSendRecv);
+  }
+  return transceiver->sender();
+}
+
+rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>>
+RtpTransmissionManager::CreateSender(
+    cricket::MediaType media_type,
+    const std::string& id,
+    rtc::scoped_refptr<MediaStreamTrackInterface> track,
+    const std::vector<std::string>& stream_ids,
+    const std::vector<RtpEncodingParameters>& send_encodings) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>> sender;
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    RTC_DCHECK(!track ||
+               (track->kind() == MediaStreamTrackInterface::kAudioKind));
+    sender = RtpSenderProxyWithInternal<RtpSenderInternal>::Create(
+        signaling_thread(),
+        AudioRtpSender::Create(worker_thread(), id, legacy_stats_, this));
+    NoteUsageEvent(UsageEvent::AUDIO_ADDED);
+  } else {
+    RTC_DCHECK_EQ(media_type, cricket::MEDIA_TYPE_VIDEO);
+    RTC_DCHECK(!track ||
+               (track->kind() == MediaStreamTrackInterface::kVideoKind));
+    sender = RtpSenderProxyWithInternal<RtpSenderInternal>::Create(
+        signaling_thread(), VideoRtpSender::Create(worker_thread(), id, this));
+    NoteUsageEvent(UsageEvent::VIDEO_ADDED);
+  }
+  bool set_track_succeeded = sender->SetTrack(track.get());
+  RTC_DCHECK(set_track_succeeded);
+  sender->internal()->set_stream_ids(stream_ids);
+  sender->internal()->set_init_send_encodings(send_encodings);
+  return sender;
+}
+
+rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
+RtpTransmissionManager::CreateReceiver(cricket::MediaType media_type,
+                                       const std::string& receiver_id) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
+      receiver;
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    receiver = RtpReceiverProxyWithInternal<RtpReceiverInternal>::Create(
+        signaling_thread(), worker_thread(),
+        rtc::make_ref_counted<AudioRtpReceiver>(worker_thread(), receiver_id,
+                                                std::vector<std::string>({}),
+                                                IsUnifiedPlan()));
+    NoteUsageEvent(UsageEvent::AUDIO_ADDED);
+  } else {
+    RTC_DCHECK_EQ(media_type, cricket::MEDIA_TYPE_VIDEO);
+    receiver = RtpReceiverProxyWithInternal<RtpReceiverInternal>::Create(
+        signaling_thread(), worker_thread(),
+        rtc::make_ref_counted<VideoRtpReceiver>(worker_thread(), receiver_id,
+                                                std::vector<std::string>({})));
+    NoteUsageEvent(UsageEvent::VIDEO_ADDED);
+  }
+  return receiver;
+}
+
+rtc::scoped_refptr<RtpTransceiverProxyWithInternal<RtpTransceiver>>
+RtpTransmissionManager::CreateAndAddTransceiver(
+    rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>> sender,
+    rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
+        receiver) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  // Ensure that the new sender does not have an ID that is already in use by
+  // another sender.
+  // Allow receiver IDs to conflict since those come from remote SDP (which
+  // could be invalid, but should not cause a crash).
+  RTC_DCHECK(!FindSenderById(sender->id()));
+  auto transceiver = RtpTransceiverProxyWithInternal<RtpTransceiver>::Create(
+      signaling_thread(),
+      rtc::make_ref_counted<RtpTransceiver>(
+          sender, receiver, context_,
+          sender->media_type() == cricket::MEDIA_TYPE_AUDIO
+              ? media_engine()->voice().GetRtpHeaderExtensions()
+              : media_engine()->video().GetRtpHeaderExtensions(),
+          [this_weak_ptr = weak_ptr_factory_.GetWeakPtr()]() {
+            if (this_weak_ptr) {
+              this_weak_ptr->OnNegotiationNeeded();
+            }
+          }));
+  transceivers()->Add(transceiver);
+  return transceiver;
+}
+
+rtc::scoped_refptr<RtpTransceiverProxyWithInternal<RtpTransceiver>>
+RtpTransmissionManager::FindFirstTransceiverForAddedTrack(
+    rtc::scoped_refptr<MediaStreamTrackInterface> track,
+    const std::vector<RtpEncodingParameters>* init_send_encodings) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(track);
+  if (init_send_encodings != nullptr) {
+    return nullptr;
+  }
+  for (auto transceiver : transceivers()->List()) {
+    if (!transceiver->sender()->track() &&
+        cricket::MediaTypeToString(transceiver->media_type()) ==
+            track->kind() &&
+        !transceiver->internal()->has_ever_been_used_to_send() &&
+        !transceiver->stopped()) {
+      return transceiver;
+    }
+  }
+  return nullptr;
+}
+
+std::vector<rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>>>
+RtpTransmissionManager::GetSendersInternal() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  std::vector<rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>>>
+      all_senders;
+  for (const auto& transceiver : transceivers_.List()) {
+    if (IsUnifiedPlan() && transceiver->internal()->stopped())
+      continue;
+
+    auto senders = transceiver->internal()->senders();
+    all_senders.insert(all_senders.end(), senders.begin(), senders.end());
+  }
+  return all_senders;
+}
+
+std::vector<
+    rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>>
+RtpTransmissionManager::GetReceiversInternal() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  std::vector<
+      rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>>
+      all_receivers;
+  for (const auto& transceiver : transceivers_.List()) {
+    if (IsUnifiedPlan() && transceiver->internal()->stopped())
+      continue;
+
+    auto receivers = transceiver->internal()->receivers();
+    all_receivers.insert(all_receivers.end(), receivers.begin(),
+                         receivers.end());
+  }
+  return all_receivers;
+}
+
+rtc::scoped_refptr<RtpTransceiverProxyWithInternal<RtpTransceiver>>
+RtpTransmissionManager::GetAudioTransceiver() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  // This method only works with Plan B SDP, where there is a single
+  // audio/video transceiver.
+  RTC_DCHECK(!IsUnifiedPlan());
+  for (auto transceiver : transceivers_.List()) {
+    if (transceiver->media_type() == cricket::MEDIA_TYPE_AUDIO) {
+      return transceiver;
+    }
+  }
+  RTC_DCHECK_NOTREACHED();
+  return nullptr;
+}
+
+rtc::scoped_refptr<RtpTransceiverProxyWithInternal<RtpTransceiver>>
+RtpTransmissionManager::GetVideoTransceiver() const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  // This method only works with Plan B SDP, where there is a single
+  // audio/video transceiver.
+  RTC_DCHECK(!IsUnifiedPlan());
+  for (auto transceiver : transceivers_.List()) {
+    if (transceiver->media_type() == cricket::MEDIA_TYPE_VIDEO) {
+      return transceiver;
+    }
+  }
+  RTC_DCHECK_NOTREACHED();
+  return nullptr;
+}
+
+void RtpTransmissionManager::AddAudioTrack(AudioTrackInterface* track,
+                                           MediaStreamInterface* stream) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(track);
+  RTC_DCHECK(stream);
+  auto sender = FindSenderForTrack(track);
+  if (sender) {
+    // We already have a sender for this track, so just change the stream_id
+    // so that it's correct in the next call to CreateOffer.
+    sender->internal()->set_stream_ids({stream->id()});
+    return;
+  }
+
+  // Normal case; we've never seen this track before.
+  auto new_sender = CreateSender(cricket::MEDIA_TYPE_AUDIO, track->id(),
+                                 rtc::scoped_refptr<AudioTrackInterface>(track),
+                                 {stream->id()}, {{}});
+  new_sender->internal()->SetMediaChannel(voice_media_send_channel());
+  GetAudioTransceiver()->internal()->AddSender(new_sender);
+  // If the sender has already been configured in SDP, we call SetSsrc,
+  // which will connect the sender to the underlying transport. This can
+  // occur if a local session description that contains the ID of the sender
+  // is set before AddStream is called. It can also occur if the local
+  // session description is not changed and RemoveStream is called, and
+  // later AddStream is called again with the same stream.
+  const RtpSenderInfo* sender_info =
+      FindSenderInfo(local_audio_sender_infos_, stream->id(), track->id());
+  if (sender_info) {
+    new_sender->internal()->SetSsrc(sender_info->first_ssrc);
+  }
+}
+
+// TODO(deadbeef): Don't destroy RtpSenders here; they should be kept around
+// indefinitely, when we have unified plan SDP.
+void RtpTransmissionManager::RemoveAudioTrack(AudioTrackInterface* track,
+                                              MediaStreamInterface* stream) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto sender = FindSenderForTrack(track);
+  if (!sender) {
+    RTC_LOG(LS_WARNING) << "RtpSender for track with id " << track->id()
+                        << " doesn't exist.";
+    return;
+  }
+  GetAudioTransceiver()->internal()->RemoveSender(sender.get());
+}
+
+void RtpTransmissionManager::AddVideoTrack(VideoTrackInterface* track,
+                                           MediaStreamInterface* stream) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(track);
+  RTC_DCHECK(stream);
+  auto sender = FindSenderForTrack(track);
+  if (sender) {
+    // We already have a sender for this track, so just change the stream_id
+    // so that it's correct in the next call to CreateOffer.
+    sender->internal()->set_stream_ids({stream->id()});
+    return;
+  }
+
+  // Normal case; we've never seen this track before.
+  auto new_sender = CreateSender(cricket::MEDIA_TYPE_VIDEO, track->id(),
+                                 rtc::scoped_refptr<VideoTrackInterface>(track),
+                                 {stream->id()}, {{}});
+  new_sender->internal()->SetMediaChannel(video_media_send_channel());
+  GetVideoTransceiver()->internal()->AddSender(new_sender);
+  const RtpSenderInfo* sender_info =
+      FindSenderInfo(local_video_sender_infos_, stream->id(), track->id());
+  if (sender_info) {
+    new_sender->internal()->SetSsrc(sender_info->first_ssrc);
+  }
+}
+
+void RtpTransmissionManager::RemoveVideoTrack(VideoTrackInterface* track,
+                                              MediaStreamInterface* stream) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto sender = FindSenderForTrack(track);
+  if (!sender) {
+    RTC_LOG(LS_WARNING) << "RtpSender for track with id " << track->id()
+                        << " doesn't exist.";
+    return;
+  }
+  GetVideoTransceiver()->internal()->RemoveSender(sender.get());
+}
+
+void RtpTransmissionManager::CreateAudioReceiver(
+    MediaStreamInterface* stream,
+    const RtpSenderInfo& remote_sender_info) {
+  RTC_DCHECK(!closed_);
+  std::vector<rtc::scoped_refptr<MediaStreamInterface>> streams;
+  streams.push_back(rtc::scoped_refptr<MediaStreamInterface>(stream));
+  // TODO(https://crbug.com/webrtc/9480): When we remove remote_streams(), use
+  // the constructor taking stream IDs instead.
+  auto audio_receiver = rtc::make_ref_counted<AudioRtpReceiver>(
+      worker_thread(), remote_sender_info.sender_id, streams, IsUnifiedPlan(),
+      voice_media_receive_channel());
+  if (remote_sender_info.sender_id == kDefaultAudioSenderId) {
+    audio_receiver->SetupUnsignaledMediaChannel();
+  } else {
+    audio_receiver->SetupMediaChannel(remote_sender_info.first_ssrc);
+  }
+
+  auto receiver = RtpReceiverProxyWithInternal<RtpReceiverInternal>::Create(
+      signaling_thread(), worker_thread(), std::move(audio_receiver));
+  GetAudioTransceiver()->internal()->AddReceiver(receiver);
+  Observer()->OnAddTrack(receiver, streams);
+  NoteUsageEvent(UsageEvent::AUDIO_ADDED);
+}
+
+void RtpTransmissionManager::CreateVideoReceiver(
+    MediaStreamInterface* stream,
+    const RtpSenderInfo& remote_sender_info) {
+  RTC_DCHECK(!closed_);
+  std::vector<rtc::scoped_refptr<MediaStreamInterface>> streams;
+  streams.push_back(rtc::scoped_refptr<MediaStreamInterface>(stream));
+  // TODO(https://crbug.com/webrtc/9480): When we remove remote_streams(), use
+  // the constructor taking stream IDs instead.
+  auto video_receiver = rtc::make_ref_counted<VideoRtpReceiver>(
+      worker_thread(), remote_sender_info.sender_id, streams);
+
+  video_receiver->SetupMediaChannel(
+      remote_sender_info.sender_id == kDefaultVideoSenderId
+          ? absl::nullopt
+          : absl::optional<uint32_t>(remote_sender_info.first_ssrc),
+      video_media_receive_channel());
+
+  auto receiver = RtpReceiverProxyWithInternal<RtpReceiverInternal>::Create(
+      signaling_thread(), worker_thread(), std::move(video_receiver));
+  GetVideoTransceiver()->internal()->AddReceiver(receiver);
+  Observer()->OnAddTrack(receiver, streams);
+  NoteUsageEvent(UsageEvent::VIDEO_ADDED);
+}
+
+// TODO(deadbeef): Keep RtpReceivers around even if track goes away in remote
+// description.
+rtc::scoped_refptr<RtpReceiverInterface>
+RtpTransmissionManager::RemoveAndStopReceiver(
+    const RtpSenderInfo& remote_sender_info) {
+  auto receiver = FindReceiverById(remote_sender_info.sender_id);
+  if (!receiver) {
+    RTC_LOG(LS_WARNING) << "RtpReceiver for track with id "
+                        << remote_sender_info.sender_id << " doesn't exist.";
+    return nullptr;
+  }
+  if (receiver->media_type() == cricket::MEDIA_TYPE_AUDIO) {
+    GetAudioTransceiver()->internal()->RemoveReceiver(receiver.get());
+  } else {
+    GetVideoTransceiver()->internal()->RemoveReceiver(receiver.get());
+  }
+  return receiver;
+}
+
+void RtpTransmissionManager::OnRemoteSenderAdded(
+    const RtpSenderInfo& sender_info,
+    MediaStreamInterface* stream,
+    cricket::MediaType media_type) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_LOG(LS_INFO) << "Creating " << cricket::MediaTypeToString(media_type)
+                   << " receiver for track_id=" << sender_info.sender_id
+                   << " and stream_id=" << sender_info.stream_id;
+
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    CreateAudioReceiver(stream, sender_info);
+  } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+    CreateVideoReceiver(stream, sender_info);
+  } else {
+    RTC_DCHECK_NOTREACHED() << "Invalid media type";
+  }
+}
+
+void RtpTransmissionManager::OnRemoteSenderRemoved(
+    const RtpSenderInfo& sender_info,
+    MediaStreamInterface* stream,
+    cricket::MediaType media_type) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_LOG(LS_INFO) << "Removing " << cricket::MediaTypeToString(media_type)
+                   << " receiver for track_id=" << sender_info.sender_id
+                   << " and stream_id=" << sender_info.stream_id;
+
+  rtc::scoped_refptr<RtpReceiverInterface> receiver;
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    // When the MediaEngine audio channel is destroyed, the RemoteAudioSource
+    // will be notified which will end the AudioRtpReceiver::track().
+    receiver = RemoveAndStopReceiver(sender_info);
+    rtc::scoped_refptr<AudioTrackInterface> audio_track =
+        stream->FindAudioTrack(sender_info.sender_id);
+    if (audio_track) {
+      stream->RemoveTrack(audio_track);
+    }
+  } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+    // Stopping or destroying a VideoRtpReceiver will end the
+    // VideoRtpReceiver::track().
+    receiver = RemoveAndStopReceiver(sender_info);
+    rtc::scoped_refptr<VideoTrackInterface> video_track =
+        stream->FindVideoTrack(sender_info.sender_id);
+    if (video_track) {
+      // There's no guarantee the track is still available, e.g. the track may
+      // have been removed from the stream by an application.
+      stream->RemoveTrack(video_track);
+    }
+  } else {
+    RTC_DCHECK_NOTREACHED() << "Invalid media type";
+  }
+  if (receiver) {
+    RTC_DCHECK(!closed_);
+    Observer()->OnRemoveTrack(receiver);
+  }
+}
+
+void RtpTransmissionManager::OnLocalSenderAdded(
+    const RtpSenderInfo& sender_info,
+    cricket::MediaType media_type) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK(!IsUnifiedPlan());
+  auto sender = FindSenderById(sender_info.sender_id);
+  if (!sender) {
+    RTC_LOG(LS_WARNING) << "An unknown RtpSender with id "
+                        << sender_info.sender_id
+                        << " has been configured in the local description.";
+    return;
+  }
+
+  if (sender->media_type() != media_type) {
+    RTC_LOG(LS_WARNING) << "An RtpSender has been configured in the local"
+                           " description with an unexpected media type.";
+    return;
+  }
+
+  sender->internal()->set_stream_ids({sender_info.stream_id});
+  sender->internal()->SetSsrc(sender_info.first_ssrc);
+}
+
+void RtpTransmissionManager::OnLocalSenderRemoved(
+    const RtpSenderInfo& sender_info,
+    cricket::MediaType media_type) {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  auto sender = FindSenderById(sender_info.sender_id);
+  if (!sender) {
+    // This is the normal case. I.e., RemoveStream has been called and the
+    // SessionDescriptions has been renegotiated.
+    return;
+  }
+
+  // A sender has been removed from the SessionDescription but it's still
+  // associated with the PeerConnection. This only occurs if the SDP doesn't
+  // match with the calls to CreateSender, AddStream and RemoveStream.
+  if (sender->media_type() != media_type) {
+    RTC_LOG(LS_WARNING) << "An RtpSender has been configured in the local"
+                           " description with an unexpected media type.";
+    return;
+  }
+
+  sender->internal()->SetSsrc(0);
+}
+
+std::vector<RtpSenderInfo>* RtpTransmissionManager::GetRemoteSenderInfos(
+    cricket::MediaType media_type) {
+  RTC_DCHECK(media_type == cricket::MEDIA_TYPE_AUDIO ||
+             media_type == cricket::MEDIA_TYPE_VIDEO);
+  return (media_type == cricket::MEDIA_TYPE_AUDIO)
+             ? &remote_audio_sender_infos_
+             : &remote_video_sender_infos_;
+}
+
+std::vector<RtpSenderInfo>* RtpTransmissionManager::GetLocalSenderInfos(
+    cricket::MediaType media_type) {
+  RTC_DCHECK(media_type == cricket::MEDIA_TYPE_AUDIO ||
+             media_type == cricket::MEDIA_TYPE_VIDEO);
+  return (media_type == cricket::MEDIA_TYPE_AUDIO) ? &local_audio_sender_infos_
+                                                   : &local_video_sender_infos_;
+}
+
+const RtpSenderInfo* RtpTransmissionManager::FindSenderInfo(
+    const std::vector<RtpSenderInfo>& infos,
+    const std::string& stream_id,
+    const std::string& sender_id) const {
+  for (const RtpSenderInfo& sender_info : infos) {
+    if (sender_info.stream_id == stream_id &&
+        sender_info.sender_id == sender_id) {
+      return &sender_info;
+    }
+  }
+  return nullptr;
+}
+
+rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>>
+RtpTransmissionManager::FindSenderForTrack(
+    MediaStreamTrackInterface* track) const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  for (const auto& transceiver : transceivers_.List()) {
+    for (auto sender : transceiver->internal()->senders()) {
+      if (sender->track() == track) {
+        return sender;
+      }
+    }
+  }
+  return nullptr;
+}
+
+rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>>
+RtpTransmissionManager::FindSenderById(const std::string& sender_id) const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  for (const auto& transceiver : transceivers_.List()) {
+    for (auto sender : transceiver->internal()->senders()) {
+      if (sender->id() == sender_id) {
+        return sender;
+      }
+    }
+  }
+  return nullptr;
+}
+
+rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
+RtpTransmissionManager::FindReceiverById(const std::string& receiver_id) const {
+  RTC_DCHECK_RUN_ON(signaling_thread());
+  for (const auto& transceiver : transceivers_.List()) {
+    for (auto receiver : transceiver->internal()->receivers()) {
+      if (receiver->id() == receiver_id) {
+        return receiver;
+      }
+    }
+  }
+  return nullptr;
+}
+
+cricket::MediaEngineInterface* RtpTransmissionManager::media_engine() const {
+  return context_->media_engine();
+}
+
+}  // namespace webrtc