Start/Stop receiving stream method for VideoTrack (#25)

* Initial implementation of start/stop receive

* move set_state call to signalling thread as well.

https://source.chromium.org/chromium/_/webrtc/src.git/+/dfd69c22100e1d2e83295f33d06fa9916caa5c53

* separate should_receive from enabled for now

* ios hooks

* Fix ios compile errors

* code cleanup

* clean up

* reuse frame buffers instead

api/media_stream_interface.cc

@@ -18,6 +18,10 @@ const char* const MediaStreamTrackInterface::kVideoKind =
 const char* const MediaStreamTrackInterface::kAudioKind =
     cricket::kMediaTypeAudio;
 
+bool VideoTrackInterface::should_receive() const {
+  return true;
+}
+
 VideoTrackInterface::ContentHint VideoTrackInterface::content_hint() const {
   return ContentHint::kNone;
 }

api/media_stream_interface.h

@@ -188,6 +188,8 @@ class RTC_EXPORT VideoTrackInterface
 
   virtual VideoTrackSourceInterface* GetSource() const = 0;
 
+  virtual void set_should_receive(bool should_receive) {}
+  virtual bool should_receive() const;
   virtual ContentHint content_hint() const;
   virtual void set_content_hint(ContentHint hint) {}
 

media/base/media_channel.h

@@ -897,6 +897,9 @@ class VideoMediaChannel : public MediaChannel, public Delayable {
   virtual void GenerateKeyFrame(uint32_t ssrc) = 0;
 
   virtual std::vector<webrtc::RtpSource> GetSources(uint32_t ssrc) const = 0;
+
+  virtual void StartReceive(uint32_t ssrc) {}
+  virtual void StopReceive(uint32_t ssrc) {}
 };
 
 // Info about data received in DataMediaChannel.  For use in

media/engine/webrtc_video_engine.cc

@@ -949,6 +949,24 @@ void WebRtcVideoChannel::RequestEncoderSwitch(
                       << format.ToString() << " not negotiated.";
 }
 
+void WebRtcVideoChannel::StartReceive(uint32_t ssrc) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  WebRtcVideoReceiveStream* stream = FindReceiveStream(ssrc);
+  if(!stream) {
+    return;
+  }
+  stream->StartStream();
+}
+
+void WebRtcVideoChannel::StopReceive(uint32_t ssrc) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  WebRtcVideoReceiveStream* stream = FindReceiveStream(ssrc);
+  if(!stream) {
+    return;
+  }
+  stream->StopStream();
+}
+
 bool WebRtcVideoChannel::ApplyChangedParams(
     const ChangedSendParameters& changed_params) {
   RTC_DCHECK_RUN_ON(&thread_checker_);
@@ -3017,6 +3035,17 @@ void WebRtcVideoChannel::WebRtcVideoReceiveStream::SetRecvParameters(
   }
 }
 
+void WebRtcVideoChannel::WebRtcVideoReceiveStream::StartStream(){
+  if (stream_) {
+    stream_->Start();
+  }
+}
+void WebRtcVideoChannel::WebRtcVideoReceiveStream::StopStream(){
+  if (stream_) {
+    stream_->Stop();
+  }
+}
+
 void WebRtcVideoChannel::WebRtcVideoReceiveStream::RecreateWebRtcVideoStream() {
   absl::optional<int> base_minimum_playout_delay_ms;
   absl::optional<webrtc::VideoReceiveStream::RecordingState> recording_state;

media/engine/webrtc_video_engine.h

@@ -245,7 +245,8 @@ class WebRtcVideoChannel : public VideoMediaChannel,
       uint32_t ssrc,
       rtc::scoped_refptr<webrtc::FrameTransformerInterface> frame_transformer)
       override;
-
+  void StartReceive(uint32_t ssrc) override;
+  void StopReceive(uint32_t ssrc) override;
  private:
   class WebRtcVideoReceiveStream;
 
@@ -479,6 +480,9 @@ class WebRtcVideoChannel : public VideoMediaChannel,
     void SetDepacketizerToDecoderFrameTransformer(
         rtc::scoped_refptr<webrtc::FrameTransformerInterface>
             frame_transformer);
+
+    void StartStream();
+    void StopStream();
 
    private:
     void RecreateWebRtcVideoStream();

modules/video_coding/frame_buffer2.cc

@@ -356,6 +356,13 @@ void FrameBuffer::SetProtectionMode(VCMVideoProtection mode) {
   protection_mode_ = mode;
 }
 
+void FrameBuffer::Start() {
+  TRACE_EVENT0("webrtc", "FrameBuffer::Stop");
+  MutexLock lock(&mutex_);
+  if (!stopped_)
+    return;
+  stopped_ = false;
+}
 void FrameBuffer::Stop() {
   TRACE_EVENT0("webrtc", "FrameBuffer::Stop");
   MutexLock lock(&mutex_);

modules/video_coding/frame_buffer2.h

@@ -78,6 +78,8 @@ class FrameBuffer {
   // Stop the frame buffer, causing any sleeping thread in NextFrame to
   // return immediately.
   void Stop();
+  // Unstop the frame buffer, re-allowing new frames to be inserted and read.
+  void Start();
 
   // Updates the RTT for jitter buffer estimation.
   void UpdateRtt(int64_t rtt_ms);

pc/media_stream_track_proxy.h

@@ -44,16 +44,18 @@ PROXY_PRIMARY_THREAD_DESTRUCTOR()
 BYPASS_PROXY_CONSTMETHOD0(std::string, kind)
 BYPASS_PROXY_CONSTMETHOD0(std::string, id)
 PROXY_SECONDARY_CONSTMETHOD0(TrackState, state)
-PROXY_SECONDARY_CONSTMETHOD0(bool, enabled)
-PROXY_SECONDARY_METHOD1(bool, set_enabled, bool)
-PROXY_SECONDARY_CONSTMETHOD0(ContentHint, content_hint)
-PROXY_SECONDARY_METHOD1(void, set_content_hint, ContentHint)
+PROXY_CONSTMETHOD0(bool, enabled)
+PROXY_METHOD1(bool, set_enabled, bool)
+PROXY_CONSTMETHOD0(ContentHint, content_hint)
+PROXY_METHOD1(void, set_content_hint, ContentHint)
 PROXY_SECONDARY_METHOD2(void,
                         AddOrUpdateSink,
                         rtc::VideoSinkInterface<VideoFrame>*,
                         const rtc::VideoSinkWants&)
 PROXY_SECONDARY_METHOD1(void, RemoveSink, rtc::VideoSinkInterface<VideoFrame>*)
 BYPASS_PROXY_CONSTMETHOD0(VideoTrackSourceInterface*, GetSource)
+PROXY_CONSTMETHOD0(bool, should_receive)
+PROXY_METHOD1(void, set_should_receive, bool)
 
 PROXY_METHOD1(void, RegisterObserver, ObserverInterface*)
 PROXY_METHOD1(void, UnregisterObserver, ObserverInterface*)

pc/rtp_sender.cc

@@ -584,10 +584,13 @@ VideoRtpSender::~VideoRtpSender() {
 }
 
 void VideoRtpSender::OnChanged() {
+  // Running on the signaling thread.
   TRACE_EVENT0("webrtc", "VideoRtpSender::OnChanged");
   RTC_DCHECK(!stopped_);
-  if (cached_track_content_hint_ != video_track()->content_hint()) {
-    cached_track_content_hint_ = video_track()->content_hint();
+
+  auto content_hint = video_track()->content_hint();
+  if (cached_track_content_hint_ != content_hint) {
+    cached_track_content_hint_ = content_hint;
     if (can_send_track()) {
       SetSend();
     }

pc/video_rtp_receiver.cc

@@ -21,6 +21,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/location.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/task_utils/to_queued_task.h"
 
 namespace webrtc {
 
@@ -46,9 +47,12 @@ VideoRtpReceiver::VideoRtpReceiver(
                                                          worker_thread,
                                                          source_),
                              worker_thread))),
-      attachment_id_(GenerateUniqueId()) {
+      cached_track_should_receive_(track_->should_receive()),
+      attachment_id_(GenerateUniqueId()),
+      worker_thread_safety_(PendingTaskSafetyFlag::CreateDetachedInactive()) {
   RTC_DCHECK(worker_thread_);
   SetStreams(streams);
+  track_->RegisterObserver(this);
   RTC_DCHECK_EQ(source_->state(), MediaSourceInterface::kLive);
 }
 
@@ -137,6 +141,39 @@ void VideoRtpReceiver::StopAndEndTrack() {
   track_->internal()->set_ended();
 }
 
+void VideoRtpReceiver::OnChanged() {
+  RTC_DCHECK_RUN_ON(&signaling_thread_checker_);
+  if (cached_track_should_receive_ != track_->should_receive()) {
+    cached_track_should_receive_ = track_->should_receive();
+    worker_thread_->PostTask(ToQueuedTask(
+        worker_thread_safety_,
+        [this, receive = cached_track_should_receive_]() {
+          RTC_DCHECK_RUN_ON(worker_thread_);
+          if(receive) {
+            StartMediaChannel();
+          } else {
+            StopMediaChannel();
+          }
+        }));
+  }
+}
+
+void VideoRtpReceiver::StartMediaChannel() {  
+  RTC_DCHECK_RUN_ON(worker_thread_);
+  if (!media_channel_) {
+    return;
+  }
+  media_channel_->StartReceive(ssrc_.value_or(0));
+  OnGenerateKeyFrame();
+}
+void VideoRtpReceiver::StopMediaChannel() {
+  RTC_DCHECK_RUN_ON(worker_thread_);
+  if (!media_channel_) {
+    return;
+  }
+  media_channel_->StopReceive(ssrc_.value_or(0));
+}
+
 void VideoRtpReceiver::RestartMediaChannel(absl::optional<uint32_t> ssrc) {
   RTC_DCHECK_RUN_ON(&signaling_thread_checker_);
 
@@ -235,6 +272,7 @@ void VideoRtpReceiver::set_transport(
 void VideoRtpReceiver::SetStreams(
     const std::vector<rtc::scoped_refptr<MediaStreamInterface>>& streams) {
   RTC_DCHECK_RUN_ON(&signaling_thread_checker_);
+
   // Remove remote track from any streams that are going away.
   for (const auto& existing_stream : streams_) {
     bool removed = true;
@@ -301,13 +339,14 @@ void VideoRtpReceiver::SetMediaChannel(cricket::MediaChannel* media_channel) {
 void VideoRtpReceiver::SetMediaChannel_w(cricket::MediaChannel* media_channel) {
   if (media_channel == media_channel_)
     return;
-
   bool encoded_sink_enabled = saved_encoded_sink_enabled_;
   if (encoded_sink_enabled && media_channel_) {
     // Turn off the old sink, if any.
     SetEncodedSinkEnabled(false);
   }
 
+  media_channel ? worker_thread_safety_->SetAlive()
+                : worker_thread_safety_->SetNotAlive();
   media_channel_ = static_cast<cricket::VideoMediaChannel*>(media_channel);
 
   if (media_channel_) {

pc/video_rtp_receiver.h

@@ -43,7 +43,8 @@
 
 namespace webrtc {
 
-class VideoRtpReceiver : public RtpReceiverInternal {
+class VideoRtpReceiver : public RtpReceiverInternal,
+                         public ObserverInterface {
  public:
   // An SSRC of 0 will create a receiver that will match the first SSRC it
   // sees. Must be called on signaling thread.
@@ -61,6 +62,9 @@ class VideoRtpReceiver : public RtpReceiverInternal {
 
   rtc::scoped_refptr<VideoTrackInterface> video_track() const { return track_; }
 
+  // ObserverInterface implementation
+  void OnChanged() override;
+
   // RtpReceiverInterface implementation
   rtc::scoped_refptr<MediaStreamTrackInterface> track() const override {
     return track_;
@@ -111,6 +115,8 @@ class VideoRtpReceiver : public RtpReceiverInternal {
   std::vector<RtpSource> GetSources() const override;
 
  private:
+  void StartMediaChannel();
+  void StopMediaChannel();
   void RestartMediaChannel(absl::optional<uint32_t> ssrc);
   void SetSink(rtc::VideoSinkInterface<VideoFrame>* sink)
       RTC_RUN_ON(worker_thread_);
@@ -165,6 +171,8 @@ class VideoRtpReceiver : public RtpReceiverInternal {
       RTC_GUARDED_BY(&signaling_thread_checker_) = nullptr;
   bool received_first_packet_ RTC_GUARDED_BY(&signaling_thread_checker_) =
       false;
+
+  bool cached_track_should_receive_ RTC_GUARDED_BY(&signaling_thread_checker_);
   const int attachment_id_;
   rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor_
       RTC_GUARDED_BY(worker_thread_);
@@ -180,6 +188,7 @@ class VideoRtpReceiver : public RtpReceiverInternal {
   // or switched.
   bool saved_generate_keyframe_ RTC_GUARDED_BY(worker_thread_) = false;
   bool saved_encoded_sink_enabled_ RTC_GUARDED_BY(worker_thread_) = false;
+  const rtc::scoped_refptr<PendingTaskSafetyFlag> worker_thread_safety_;
 };
 
 }  // namespace webrtc

pc/video_track.cc

@@ -19,6 +19,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/location.h"
 #include "rtc_base/ref_counted_object.h"
+#include "rtc_base/logging.h"
 
 namespace webrtc {
 
@@ -53,7 +54,7 @@ void VideoTrack::AddOrUpdateSink(rtc::VideoSinkInterface<VideoFrame>* sink,
   RTC_DCHECK_RUN_ON(worker_thread_);
   VideoSourceBaseGuarded::AddOrUpdateSink(sink, wants);
   rtc::VideoSinkWants modified_wants = wants;
-  modified_wants.black_frames = !enabled();
+  modified_wants.black_frames = !enabled_w_;
   video_source_->AddOrUpdateSink(sink, modified_wants);
 }
 
@@ -68,31 +69,56 @@ VideoTrackSourceInterface* VideoTrack::GetSource() const {
   return video_source_.get();
 }
 
+void VideoTrack::set_should_receive(bool receive) {
+  RTC_DCHECK_RUN_ON(&signaling_thread_);
+  if (should_receive_ == receive)
+    return;
+  should_receive_ = receive;
+  Notifier<VideoTrackInterface>::FireOnChanged();
+}
+
+bool VideoTrack::should_receive() const {
+  RTC_DCHECK_RUN_ON(&signaling_thread_);
+  return should_receive_;
+}
+
 VideoTrackInterface::ContentHint VideoTrack::content_hint() const {
-  RTC_DCHECK_RUN_ON(worker_thread_);
+  RTC_DCHECK_RUN_ON(&signaling_thread_);
   return content_hint_;
 }
 
 void VideoTrack::set_content_hint(ContentHint hint) {
-  RTC_DCHECK_RUN_ON(worker_thread_);
+  RTC_DCHECK_RUN_ON(&signaling_thread_);
   if (content_hint_ == hint)
     return;
   content_hint_ = hint;
   Notifier<VideoTrackInterface>::FireOnChanged();
 }
 
 bool VideoTrack::set_enabled(bool enable) {
-  RTC_DCHECK_RUN_ON(worker_thread_);
-  for (auto& sink_pair : sink_pairs()) {
-    rtc::VideoSinkWants modified_wants = sink_pair.wants;
-    modified_wants.black_frames = !enable;
-    video_source_->AddOrUpdateSink(sink_pair.sink, modified_wants);
-  }
-  return MediaStreamTrack<VideoTrackInterface>::set_enabled(enable);
+  RTC_DCHECK_RUN_ON(&signaling_thread_);
+
+  bool ret = MediaStreamTrack<VideoTrackInterface>::set_enabled(enable);
+
+  worker_thread_->Invoke<void>(RTC_FROM_HERE, [&]() {
+    RTC_DCHECK_RUN_ON(worker_thread_);
+    enabled_w_ = enable;
+    for (auto& sink_pair : sink_pairs()) {
+      rtc::VideoSinkWants modified_wants = sink_pair.wants;
+      modified_wants.black_frames = !enable;
+      video_source_->AddOrUpdateSink(sink_pair.sink, modified_wants);
+    }
+  });
+
+  return ret;
 }
 
 bool VideoTrack::enabled() const {
-  RTC_DCHECK_RUN_ON(worker_thread_);
+  if (worker_thread_->IsCurrent()) {
+    RTC_DCHECK_RUN_ON(worker_thread_);
+    return enabled_w_;
+  }
+  RTC_DCHECK_RUN_ON(&signaling_thread_);
   return MediaStreamTrack<VideoTrackInterface>::enabled();
 }
 
@@ -103,15 +129,9 @@ MediaStreamTrackInterface::TrackState VideoTrack::state() const {
 
 void VideoTrack::OnChanged() {
   RTC_DCHECK_RUN_ON(&signaling_thread_);
-  worker_thread_->Invoke<void>(
-      RTC_FROM_HERE, [this, state = video_source_->state()]() {
-        // TODO(tommi): Calling set_state() this way isn't ideal since we're
-        // currently blocking the signaling thread and set_state() may
-        // internally fire notifications via `FireOnChanged()` which may further
-        // amplify the blocking effect on the signaling thread.
-        rtc::Thread::ScopedDisallowBlockingCalls no_blocking_calls;
-        set_state(state == MediaSourceInterface::kEnded ? kEnded : kLive);
-      });
+  rtc::Thread::ScopedDisallowBlockingCalls no_blocking_calls;
+  MediaSourceInterface::SourceState state = video_source_->state();
+  set_state(state == MediaSourceInterface::kEnded ? kEnded : kLive);
 }
 
 rtc::scoped_refptr<VideoTrack> VideoTrack::Create(