Merge 21611 - Implemented proper pausethenseek behaviour for the media pipeli...

media/filters/audio_renderer_base.h

 // Copyright (c) 2009 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.
 
 // AudioRendererBase takes care of the tricky queuing work and provides simple
 // methods for subclasses to peek and poke at audio data.  In addition to
 // AudioRenderer interface methods this classes doesn't implement, subclasses
 // must also implement the following methods:
 //   OnInitialized
 //   OnStop
@@ skipping 12 matching lines @@
 #include "base/lock.h"
 #include "media/base/buffers.h"
 #include "media/base/factory.h"
 #include "media/base/filters.h"
 
 namespace media {
 
 class AudioRendererBase : public AudioRenderer {
  public:
   // MediaFilter implementation.
+  virtual void Play(FilterCallback* callback);
+  virtual void Pause(FilterCallback* callback);
   virtual void Stop();
 
   virtual void Seek(base::TimeDelta time, FilterCallback* callback);
 
   // AudioRenderer implementation.
   virtual void Initialize(AudioDecoder* decoder, FilterCallback* callback);
 
  protected:
   // The default maximum size of the queue.
   static const size_t kDefaultMaxQueueSize;
 
   // Only allow a factory to create this class.
   explicit AudioRendererBase(size_t max_queue_size);
   virtual ~AudioRendererBase();
 
   // Called by Initialize().  |media_format| is the format of the AudioDecoder.
   // Subclasses should return true if they were able to initialize, false
   // otherwise.
   virtual bool OnInitialize(const MediaFormat& media_format) = 0;
 
   // Called by Stop().  Subclasses should perform any necessary cleanup during
   // this time, such as stopping any running threads.
   virtual void OnStop() = 0;
 
-  // Called when a AudioDecoder::Read() completes.
+  // Called when a AudioDecoder::Read() completes and decrements
+  // |pending_reads_|.
   virtual void OnReadComplete(Buffer* buffer_in);
 
   // Fills the given buffer with audio data by dequeuing buffers and copying the
   // data into the |dest|.  FillBuffer() also takes care of updating the clock.
   // Returns the number of bytes copied into |dest|, which may be less than
   // equal to |len|.
   //
   // If this method is returns less bytes than |len| (including zero), it could
   // be a sign that the pipeline is stalled or unable to stream the data fast
   // enough.  In such scenarios, the callee should zero out unused portions
@@ skipping 12 matching lines @@
                     float rate,
                     const base::TimeDelta& playback_delay);
 
   // Helper to parse a media format and return whether we were successful
   // retrieving all the information we care about.
   static bool ParseMediaFormat(const MediaFormat& media_format,
                                int* channels_out, int* sample_rate_out,
                                int* sample_bits_out);
 
  private:
-  // Helper method that schedules an asynchronous read from the decoder.
+  // Helper method that schedules an asynchronous read from the decoder and
+  // increments |pending_reads_|.
   //
   // Safe to call from any thread.
-  void ScheduleRead();
+  void ScheduleRead_Locked();
 
   // Audio decoder.
   scoped_refptr<AudioDecoder> decoder_;
 
   // Maximum queue size, configuration parameter passed in during construction.
   size_t max_queue_size_;
 
   // Queued audio data.
   typedef std::deque< scoped_refptr<Buffer> > BufferQueue;
   BufferQueue queue_;
   Lock lock_;
 
   // Remembers the amount of remaining audio data for the front buffer.
   size_t data_offset_;
 
-  // Whether or not we're initialized.
-  bool initialized_;
+  // Simple state tracking variable.
+  enum State {
+    kUninitialized,
+    kPaused,
+    kSeeking,
+    kPlaying,
+    kStopped,
+    kError,
+  };
+  State state_;
 
-  // Whether or not we've stopped.
-  bool stopped_;
+  // Keeps track of our pending reads.  We *must* have no pending reads before
+  // executing the pause callback, otherwise we breach the contract that all
+  // filters are idling.
+  //
+  // We use size_t since we compare against std::deque::size().
+  size_t pending_reads_;
 
   // Audio time at end of last call to FillBuffer().
   // TODO(ralphl): Update this value after seeking.
   base::TimeDelta last_fill_buffer_time_;
 
   // Filter callbacks.
-  scoped_ptr<FilterCallback> initialize_callback_;
+  scoped_ptr<FilterCallback> pause_callback_;
+  scoped_ptr<FilterCallback> seek_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioRendererBase);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_AUDIO_RENDERER_BASE_H_