preparation for recycling buffer, patch 2

media/base/filters.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Filters are connected in a strongly typed manner, with downstream filters
 // always reading data from upstream filters.  Upstream filters have no clue
 // who is actually reading from them, and return the results via callbacks.
 //
 //                         DemuxerStream(Video) <- VideoDecoder <- VideoRenderer
 // DataSource <- Demuxer <
@@ skipping 74 matching lines @@
     DCHECK(!message_loop_);
     message_loop_ = message_loop;
   }
 
   virtual MessageLoop* message_loop() {
     return message_loop_;
   }
 
   // The pipeline has resumed playback.  Filters can continue requesting reads.
   // Filters may implement this method if they need to respond to this call.
-  // TODO(boliu): Check that callback is not NULL in sublcasses.
+  // TODO(boliu): Check that callback is not NULL in subclasses.
   virtual void Play(FilterCallback* callback) {
     DCHECK(callback);
     if (callback) {
       callback->Run();
       delete callback;
     }
   }
 
-  // The pipeline has paused playback.  Filters should fulfill any existing read
-  // requests and then idle.  Filters may implement this method if they need to
-  // respond to this call.
-  // TODO(boliu): Check that callback is not NULL in sublcasses.
+  // The pipeline has paused playback.  Filters should stop buffer exchange.
+  // Filters may implement this method if they need to respond to this call.
+  // TODO(boliu): Check that callback is not NULL in subclasses.
   virtual void Pause(FilterCallback* callback) {
     DCHECK(callback);
     if (callback) {
       callback->Run();
       delete callback;
     }
   }
 
+  // The pipeline has been flushed.  Filters should return buffer to owners.
+  // Filters may implement this method if they need to respond to this call.
+  // TODO(boliu): Check that callback is not NULL in subclasses.
+  virtual void Flush(FilterCallback* callback) {
+    DCHECK(callback);
+    if (callback) {
+      callback->Run();
+      delete callback;
+    }
+  }
+
   // The pipeline is being stopped either as a result of an error or because
   // the client called Stop().
-  // TODO(boliu): Check that callback is not NULL in sublcasses.
+  // TODO(boliu): Check that callback is not NULL in subclasses.
   virtual void Stop(FilterCallback* callback) {
     DCHECK(callback);
     if (callback) {
       callback->Run();
       delete callback;
     }
   }
 
   // The pipeline playback rate has been changed.  Filters may implement this
   // method if they need to respond to this call.
@@ skipping 157 matching lines @@
   }
   FillBufferDoneCallback* fill_buffer_done_callback() {
     return fill_buffer_done_callback_.get();
   }
 
   // Render provides an output buffer for Decoder to write to. These buffers
   // will be recycled to renderer by fill_buffer_done_callback_;
   // We could also pass empty pointer here to let decoder provide buffers pool.
   virtual void FillThisBuffer(scoped_refptr<VideoFrame> frame) = 0;
 
+  // Indicate whether decoder provides its own output buffers
+  virtual bool ProvidesBuffer() = 0;
+
  private:
   scoped_ptr<FillBufferDoneCallback> fill_buffer_done_callback_;
 };
 
 
 class AudioDecoder : public MediaFilter {
  public:
   static FilterType filter_type() {
     return FILTER_AUDIO_DECODER;
   }
@@ skipping 68 matching lines @@
   // buffer.
   virtual bool HasEnded() = 0;
 
   // Sets the output volume.
   virtual void SetVolume(float volume) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_FILTERS_H_