Simplify VideoDecodeEngine interface by making everything synchronous.

media/base/filters.h

Index: media/base/filters.h
diff --git a/media/base/filters.h b/media/base/filters.h
index 1624a60b0ebfd4fab9c88909c3e0c0089a61d9b8..cfa0a4bdf9bd12e399267cc9731583f2037ae472 100644
--- a/media/base/filters.h
+++ b/media/base/filters.h
@@ -164,22 +164,17 @@ class MEDIA_EXPORT VideoDecoder : public Filter {
   // Initialize a VideoDecoder with the given DemuxerStream, executing the
   // callback upon completion.
   // stats_callback is used to update global pipeline statistics.
+  //
+  // TODO(scherkus): switch to PipelineStatus callback.
   virtual void Initialize(DemuxerStream* stream, const base::Closure& callback,
                           const StatisticsCallback& stats_callback) = 0;
 
-  // Renderer provides an output buffer for Decoder to write to. These buffers
-  // will be recycled to renderer via the permanent callback.
+  // Request a frame to be decoded and returned via the provided callback.
+  // Only one read may be in flight at any given time.
   //
-  // We could also pass empty pointer here to let decoder provide buffers pool.
-  virtual void ProduceVideoFrame(scoped_refptr<VideoFrame> frame) = 0;
-
-  // Installs a permanent callback for passing decoded video output.
-  //
-  // A NULL frame represents a decoding error.
-  typedef base::Callback<void(scoped_refptr<VideoFrame>)> ConsumeVideoFrameCB;
-  void set_consume_video_frame_callback(const ConsumeVideoFrameCB& callback) {
-    consume_video_frame_callback_ = callback;
-  }
+  // Frames will be non-NULL yet may be end of stream frames.
+  typedef base::Callback<void(scoped_refptr<VideoFrame>)> FrameReadyCB;

[acolwell GONE FROM CHROMIUM, 2011/11/01 18:31:03]

Rename to ReadCB or ReadCallback? This is just to avoid confusion when looking
at other code. read_cb_ is a little clearer than frame_ready_cb_ when trying to
evaluate where the callback came from.

[Ami GONE FROM CHROMIUM, 2011/11/01 22:17:40]

FWIW, we decided a long time ago to use *CB for the new-style callbacks.  I hope
we keep that.

[scherkus (not reviewing), 2011/11/03 04:55:59]

Renamed to ReadCB (I am fond of the shortness!) but left the bound callback
methods in VideoRendererBase and FFmpegVideoDecoderTest as FrameReady()

+  virtual void Read(const FrameReadyCB& callback) = 0;
 
   // Returns the natural width and height of decoded video in pixels.
   //
@@ -191,19 +186,8 @@ class MEDIA_EXPORT VideoDecoder : public Filter {
   virtual gfx::Size natural_size() = 0;
 
  protected:
-  // Executes the permanent callback to pass off decoded video.
-  //
-  // TODO(scherkus): name this ConsumeVideoFrame() once we fix the TODO in

[Ami GONE FROM CHROMIUM, 2011/11/01 22:17:40]

I, for one, welcome our new reduced-craxy overlords.

-  // VideoDecodeEngine::EventHandler to remove ConsumeVideoFrame() from there.
-  void VideoFrameReady(scoped_refptr<VideoFrame> frame) {
-    consume_video_frame_callback_.Run(frame);
-  }
-
   VideoDecoder();
   virtual ~VideoDecoder();
-
- private:
-  ConsumeVideoFrameCB consume_video_frame_callback_;
 };
 
 
@@ -212,6 +196,8 @@ class MEDIA_EXPORT AudioDecoder : public Filter {
   // Initialize a AudioDecoder with the given DemuxerStream, executing the
   // callback upon completion.
   // stats_callback is used to update global pipeline statistics.
+  //
+  // TODO(scherkus): switch to PipelineStatus callback.
   virtual void Initialize(DemuxerStream* stream, const base::Closure& callback,
                           const StatisticsCallback& stats_callback) = 0;