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diff --git a/dom/media/mediasink/MediaSink.h b/dom/media/mediasink/MediaSink.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MediaSink_h_
+#define MediaSink_h_
+
+#include "MediaInfo.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/MediaDebugInfoBinding.h"
+#include "nsISupportsImpl.h"
+
+class AudioDeviceInfo;
+
+namespace mozilla {
+
+class TimeStamp;
+class VideoFrameContainer;
+
+/**
+ * A consumer of audio/video data which plays audio and video tracks and
+ * manages A/V sync between them.
+ *
+ * A typical sink sends audio/video outputs to the speaker and screen.
+ * However, there are also sinks which capture the output of an media element
+ * and send the output to a MediaStream.
+ *
+ * This class is used to move A/V sync management and audio/video rendering
+ * out of MDSM so it is possible for subclasses to do external rendering using
+ * specific hardware which is required by TV projects and CDM.
+ *
+ * Note this class is not thread-safe and should be called from the state
+ * machine thread only.
+ */
+class MediaSink {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaSink);
+  typedef mozilla::TrackInfo::TrackType TrackType;
+
+  // EndedPromise needs to be a non-exclusive promise as it is shared between
+  // both the AudioSink and VideoSink.
+  typedef MozPromise<bool, nsresult, /* IsExclusive = */ false> EndedPromise;
+
+  // Return a promise which is resolved when the track finishes
+  // or null if no such track.
+  // Must be called after playback starts.
+  virtual RefPtr<EndedPromise> OnEnded(TrackType aType) = 0;
+
+  // Return the end time of the audio/video data that has been consumed
+  // or 0 if no such track.
+  // Must be called after playback starts.
+  virtual media::TimeUnit GetEndTime(TrackType aType) const = 0;
+
+  // Return playback position of the media.
+  // Since A/V sync is always maintained by this sink, there is no need to
+  // specify whether we want to get audio or video position.
+  // aTimeStamp returns the timeStamp corresponding to the returned position
+  // which is used by the compositor to derive the render time of video frames.
+  // Must be called after playback starts.
+  virtual media::TimeUnit GetPosition(TimeStamp* aTimeStamp = nullptr) = 0;
+
+  // Return true if there are data consumed but not played yet.
+  // Can be called in any state.
+  virtual bool HasUnplayedFrames(TrackType aType) const = 0;
+
+  // Return the duration of data consumed but not played yet.
+  // Can be called in any state.
+  virtual media::TimeUnit UnplayedDuration(TrackType aType) const = 0;
+
+  // Set volume of the audio track.
+  // Do nothing if this sink has no audio track.
+  // Can be called in any state.
+  virtual void SetVolume(double aVolume) {}
+
+  // Set the audio stream name.
+  // Does nothing if this sink has no audio stream.
+  // Can be called in any state.
+  virtual void SetStreamName(const nsAString& aStreamName) {}
+
+  // Set the playback rate.
+  // Can be called in any state.
+  virtual void SetPlaybackRate(double aPlaybackRate) {}
+
+  // Whether to preserve pitch of the audio track.
+  // Do nothing if this sink has no audio track.
+  // Can be called in any state.
+  virtual void SetPreservesPitch(bool aPreservesPitch) {}
+
+  // Pause/resume the playback. Only work after playback starts.
+  virtual void SetPlaying(bool aPlaying) = 0;
+
+  // Get the playback rate.
+  // Can be called in any state.
+  virtual double PlaybackRate() const = 0;
+
+  // Single frame rendering operation may need to be done before playback
+  // started (1st frame) or right after seek completed or playback stopped.
+  // Do nothing if this sink has no video track. Can be called in any state.
+  virtual void Redraw(const VideoInfo& aInfo){};
+
+  // Begin a playback session with the provided start time and media info.
+  // Must be called when playback is stopped.
+  virtual nsresult Start(const media::TimeUnit& aStartTime,
+                         const MediaInfo& aInfo) = 0;
+
+  // Finish a playback session.
+  // Must be called after playback starts.
+  virtual void Stop() = 0;
+
+  // Return true if playback has started.
+  // Can be called in any state.
+  virtual bool IsStarted() const = 0;
+
+  // Return true if playback is started and not paused otherwise false.
+  // Can be called in any state.
+  virtual bool IsPlaying() const = 0;
+
+  // The audio output device this MediaSink is playing audio data to. The
+  // default device is used if this returns null.
+  virtual const AudioDeviceInfo* AudioDevice() const = 0;
+
+  // Called on the state machine thread to shut down the sink. All resources
+  // allocated by this sink should be released.
+  // Must be called after playback stopped.
+  virtual void Shutdown() {}
+
+  virtual void SetSecondaryVideoContainer(VideoFrameContainer* aSecondary) {}
+
+  virtual void GetDebugInfo(dom::MediaSinkDebugInfo& aInfo) {}
+
+  virtual void EnableTreatAudioUnderrunAsSilence(bool aEnabled) {}
+
+ protected:
+  virtual ~MediaSink() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // MediaSink_h_