media/base/video_renderer_sink.h

   1 // Copyright 2015 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_BASE_VIDEO_RENDERER_SINK_H_
   6 #define MEDIA_BASE_VIDEO_RENDERER_SINK_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/logging.h"
  10 #include "base/memory/ref_counted.h"
  11 #include "base/time/time.h"
  12 #include "media/base/media_export.h"
  13 #include "media/base/video_frame.h"
  14
  15 namespace media {
  16
  17 // VideoRendererSink is an interface representing the end-point for rendered
  18 // video frames.  An implementation is expected to periodically call Render() on
  19 // a callback object.
  20 class MEDIA_EXPORT VideoRendererSink {
  21  public:
  22   class RenderCallback {
  23    public:
  24     // Returns a VideoFrame for rendering which should be displayed within the
  25     // presentation interval [|deadline_min|, |deadline_max|].  Returns NULL if
  26     // no frame or no new frame (since the last Render() call) is available for
  27     // rendering within the requested interval.  Intervals are expected to be
  28     // regular, contiguous, and monotonically increasing.  Irregular intervals
  29     // may affect the rendering decisions made by the underlying callback.
  30     //
  31     // If |background_rendering| is true, the VideoRenderSink is pumping
  32     // callbacks at a lower frequency than normal and the results of the
  33     // Render() call may not be used.
  34     virtual scoped_refptr<VideoFrame> Render(base::TimeTicks deadline_min,
  35                                              base::TimeTicks deadline_max,
  36                                              bool background_rendering) = 0;
  37
  38     // Called by the sink when a VideoFrame previously returned via Render() was
  39     // not actually rendered.  Must be called before the next Render() call.
  40     virtual void OnFrameDropped() = 0;
  41
  42     virtual ~RenderCallback() {}
  43   };
  44
  45   // Starts video rendering.  See RenderCallback for more details.  Must be
  46   // called to receive Render() callbacks.  Callbacks may start immediately, so
  47   // |callback| must be ready to receive callbacks before calling Start().
  48   virtual void Start(RenderCallback* callback) = 0;
  49
  50   // Stops video rendering, waits for any outstanding calls to the |callback|
  51   // given to Start() to complete before returning.  No new calls to |callback|
  52   // will be issued after this method returns.  May be used as a means of power
  53   // conservation by the sink implementation, so clients should call this
  54   // liberally if no new frames are expected.
  55   virtual void Stop() = 0;
  56
  57   // Instead of using a callback driven rendering path, allow clients to paint
  58   // frames as they see fit without regard for the compositor.
  59   // TODO(dalecurtis): This should be nuked once experiments show the new path
  60   // is amazing and the old path is not! http://crbug.com/439548
  61   virtual void PaintFrameUsingOldRenderingPath(
  62       const scoped_refptr<VideoFrame>& frame) = 0;
  63
  64   // TODO(dalecurtis): We may need OnSizeChanged() and OnOpacityChanged()
  65   // methods on this interface if background rendering is handled inside of
  66   // the media layer instead of by VideoFrameCompositor.
  67
  68   virtual ~VideoRendererSink() {}
  69 };
  70
  71 }  // namespace media
  72
  73 #endif  // MEDIA_BASE_VIDEO_RENDERER_SINK_H_