media/blink/video_frame_compositor.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
   6 #define MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
   7
   8 #include "base/callback.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "base/single_thread_task_runner.h"
  11 #include "base/synchronization/lock.h"
  12 #include "cc/layers/video_frame_provider.h"
  13 #include "media/base/media_export.h"
  14 #include "media/base/video_renderer_sink.h"
  15 #include "ui/gfx/geometry/size.h"
  16
  17 namespace media {
  18 class VideoFrame;
  19
  20 // VideoFrameCompositor acts as a bridge between the media and cc layers for
  21 // rendering video frames. I.e. a media::VideoRenderer will talk to this class
  22 // from the media side, while a cc::VideoFrameProvider::Client will talk to it
  23 // from the cc side.
  24 //
  25 // This class is responsible for requesting new frames from a video renderer in
  26 // response to requests from the VFP::Client. Since the VFP::Client may stop
  27 // issuing requests in response to visibility changes it is also responsible for
  28 // ensuring the "freshness" of the current frame for programmatic frame
  29 // requests; e.g., Canvas.drawImage() requests
  30 //
  31 // This class is also responsible for detecting frames dropped by the compositor
  32 // after rendering and signaling that information to a RenderCallback. It
  33 // detects frames not dropped by verifying each GetCurrentFrame() is followed
  34 // by a PutCurrentFrame() before the next UpdateCurrentFrame() call.
  35 //
  36 // VideoRenderSink::RenderCallback implementations must call Start() and Stop()
  37 // once new frames are expected or are no longer expected to be ready; this data
  38 // is relayed to the compositor to avoid extraneous callbacks.
  39 //
  40 // VideoFrameCompositor must live on the same thread as the compositor, though
  41 // it may be constructed on any thread.
  42 class MEDIA_EXPORT VideoFrameCompositor
  43     : public VideoRendererSink,
  44       NON_EXPORTED_BASE(public cc::VideoFrameProvider) {
  45  public:
  46   // |compositor_task_runner| is the task runner on which this class will live,
  47   // though it may be constructed on any thread.
  48   //
  49   // |natural_size_changed_cb| is run with the new natural size of the video
  50   // frame whenever a change in natural size is detected. It is not called the
  51   // first time UpdateCurrentFrame() is called. Run on the same thread as the
  52   // caller of UpdateCurrentFrame().
  53   //
  54   // |opacity_changed_cb| is run when a change in opacity is detected. It *is*
  55   // called the first time UpdateCurrentFrame() is called. Run on the same
  56   // thread as the caller of UpdateCurrentFrame().
  57   //
  58   // TODO(dalecurtis): Investigate the inconsistency between the callbacks with
  59   // respect to why we don't call |natural_size_changed_cb| on the first frame.
  60   // I suspect it was for historical reasons that no longer make sense.
  61   VideoFrameCompositor(
  62       const scoped_refptr<base::SingleThreadTaskRunner>& compositor_task_runner,
  63       const base::Callback<void(gfx::Size)>& natural_size_changed_cb,
  64       const base::Callback<void(bool)>& opacity_changed_cb);
  65
  66   // Destruction must happen on the compositor thread; Stop() must have been
  67   // called before destruction starts.
  68   ~VideoFrameCompositor() override;
  69
  70   // Returns |current_frame_| if it was refreshed recently; otherwise, if
  71   // |callback_| is available, requests a new frame and returns that one.
  72   //
  73   // This is required for programmatic frame requests where the compositor may
  74   // have stopped issuing UpdateCurrentFrame() callbacks in response to
  75   // visibility changes in the output layer.
  76   scoped_refptr<VideoFrame> GetCurrentFrameAndUpdateIfStale();
  77
  78   // cc::VideoFrameProvider implementation. These methods must be called on the
  79   // |compositor_task_runner_|.
  80   void SetVideoFrameProviderClient(
  81       cc::VideoFrameProvider::Client* client) override;
  82   bool UpdateCurrentFrame(base::TimeTicks deadline_min,
  83                           base::TimeTicks deadline_max) override;
  84   scoped_refptr<VideoFrame> GetCurrentFrame() override;
  85   void PutCurrentFrame() override;
  86
  87   // VideoRendererSink implementation. These methods must be called from the
  88   // same thread (typically the media thread).
  89   void Start(RenderCallback* callback) override;
  90   void Stop() override;
  91   void PaintFrameUsingOldRenderingPath(
  92       const scoped_refptr<VideoFrame>& frame) override;
  93
  94  private:
  95   // Called on the compositor thread to start or stop rendering if rendering was
  96   // previously started or stopped before we had a |callback_|.
  97   void OnRendererStateUpdate();
  98
  99   scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
 100
 101   // These callbacks are executed on the compositor thread.
 102   base::Callback<void(gfx::Size)> natural_size_changed_cb_;
 103   base::Callback<void(bool)> opacity_changed_cb_;
 104
 105   // These values are only set and read on the compositor thread.
 106   cc::VideoFrameProvider::Client* client_;
 107   scoped_refptr<VideoFrame> current_frame_;
 108
 109   // These values are updated and read from the media and compositor threads.
 110   base::Lock lock_;
 111   bool rendering_;
 112   VideoRendererSink::RenderCallback* callback_;
 113
 114   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 115 };
 116
 117 }  // namespace media
 118
 119 #endif  // MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_