media/base/video_broadcaster.h

/*
 *  Copyright (c) 2016 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.
 */

#ifndef MEDIA_BASE_VIDEO_BROADCASTER_H_
#define MEDIA_BASE_VIDEO_BROADCASTER_H_

#include "api/media_stream_interface.h"
#include "api/scoped_refptr.h"
#include "api/sequence_checker.h"
#include "api/video/video_frame_buffer.h"
#include "api/video/video_source_interface.h"
#include "media/base/video_source_base.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/thread_annotations.h"

namespace rtc {

// VideoBroadcaster broadcast video frames to sinks and combines VideoSinkWants
// from its sinks. It does that by implementing rtc::VideoSourceInterface and
// rtc::VideoSinkInterface. The class is threadsafe; methods may be called on
// any thread. This is needed because VideoStreamEncoder calls AddOrUpdateSink
// both on the worker thread and on the encoder task queue.
class VideoBroadcaster : public VideoSourceBase,
                         public VideoSinkInterface<webrtc::VideoFrame> {
 public:
  VideoBroadcaster();
  ~VideoBroadcaster() override;

  // Adds a new, or updates an already existing sink. If the sink is new and
  // ProcessConstraints has been called previously, the new sink's
  // OnConstraintsCalled method will be invoked with the most recent
  // constraints.
  void AddOrUpdateSink(VideoSinkInterface<webrtc::VideoFrame>* sink,
                       const VideoSinkWants& wants) override;
  void RemoveSink(VideoSinkInterface<webrtc::VideoFrame>* sink) override;

  // Returns true if the next frame will be delivered to at least one sink.
  bool frame_wanted() const;

  // Returns VideoSinkWants a source is requested to fulfill. They are
  // aggregated by all VideoSinkWants from all sinks.
  VideoSinkWants wants() const;

  // This method ensures that if a sink sets rotation_applied == true,
  // it will never receive a frame with pending rotation. Our caller
  // may pass in frames without precise synchronization with changes
  // to the VideoSinkWants.
  void OnFrame(const webrtc::VideoFrame& frame) override;

  void OnDiscardedFrame() override;

  // Called on the network thread when constraints change. Forwards the
  // constraints to sinks added with AddOrUpdateSink via OnConstraintsChanged.
  void ProcessConstraints(
      const webrtc::VideoTrackSourceConstraints& constraints);

 protected:
  void UpdateWants() RTC_EXCLUSIVE_LOCKS_REQUIRED(sinks_and_wants_lock_);
  const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& GetBlackFrameBuffer(
      int width,
      int height) RTC_EXCLUSIVE_LOCKS_REQUIRED(sinks_and_wants_lock_);

  mutable webrtc::Mutex sinks_and_wants_lock_;

  VideoSinkWants current_wants_ RTC_GUARDED_BY(sinks_and_wants_lock_);
  rtc::scoped_refptr<webrtc::VideoFrameBuffer> black_frame_buffer_;
  bool previous_frame_sent_to_all_sinks_ RTC_GUARDED_BY(sinks_and_wants_lock_) =
      true;
  absl::optional<webrtc::VideoTrackSourceConstraints> last_constraints_
      RTC_GUARDED_BY(sinks_and_wants_lock_);
};

}  // namespace rtc

#endif  // MEDIA_BASE_VIDEO_BROADCASTER_H_