Move AudioRenderer out of Filter heirarchy.

media/base/audio_renderer.h

 // Copyright (c) 2012 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.
 
 #ifndef MEDIA_BASE_AUDIO_RENDERER_H_
 #define MEDIA_BASE_AUDIO_RENDERER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/time.h"
 #include "media/base/filters.h"
 #include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
 
 namespace media {
 
 class AudioDecoder;
 
-class MEDIA_EXPORT AudioRenderer : public Filter {
+// TODO(scherkus): replace this interface with additional callbacks passed to
+// Initialize() similar to the underflow and time update callbacks.
+class MEDIA_EXPORT AudioRendererHost {
  public:
-  // Used to update the pipeline's clock time. The first parameter is the
-  // current time, and the second parameter is the time that the clock must not
-  // exceed.
+  virtual ~AudioRendererHost() {};
+
+  // Notifcation that audio rendering has reached the end of the stream.

[acolwell GONE FROM CHROMIUM, 2012/07/10 16:34:37]

nit: s/Notifcation/Notification

[scherkus (not reviewing), 2012/07/17 03:43:00]

Done.

+  virtual void AudioRendererEnded() = 0;
+
+  // Notification that audio rendering has been disabled due to external factors
+  // (i.e., device was removed). Time update callbacks will no longer be
+  // executed.
+  virtual void AudioRendererDisabled() = 0;
+};
+
+class MEDIA_EXPORT AudioRenderer
+    : public base::RefCountedThreadSafe<AudioRenderer> {
+ public:
+  // Assigns the host object responsible for this AudioRenderer. Must be set
+  // prior to calling Initialize(). The host is expected to outlive the
+  // lifetime of an AudioRenderer.
+  virtual void SetHost(AudioRendererHost* host) = 0;
+
+  // Called whenever time has advanced by way of audio rendering. The first
+  // parameter is the current time, and the second parameter is the time that
+  // the clock must not exceed.
   typedef base::Callback<void(base::TimeDelta, base::TimeDelta)> TimeCB;
 
   // Initialize a AudioRenderer with the given AudioDecoder, executing the
   // |init_cb| upon completion. |underflow_cb| is called when the
   // renderer runs out of data to pass to the audio card during playback.
   // If the |underflow_cb| is called ResumeAfterUnderflow() must be called
   // to resume playback. Pause(), Seek(), or Stop() cancels the underflow
   // condition.
   virtual void Initialize(const scoped_refptr<AudioDecoder>& decoder,
                           const PipelineStatusCB& init_cb,
                           const base::Closure& underflow_cb,
                           const TimeCB& time_cb) = 0;
 
-  // Returns true if this filter has received and processed an end-of-stream
-  // buffer.
+  // Start audio decoding and rendering at the current playback rate, executing
+  // |callback| when playback is underway.
+  virtual void Play(const base::Closure& callback) = 0;
+
+  // Temporarily suspend decoding and rendering audio, executing |callback| when
+  // playback has been suspended.
+  virtual void Pause(const base::Closure& callback) = 0;
+
+  // Discard any audio data, executing |callback| when completed.
+  virtual void Flush(const base::Closure& callback) = 0;
+
+  // Start prerolling audio data for samples starting at |time|, executing
+  // |callback| when completed.
+  //
+  // Only valid to call after a successful Initialize() or Flush().
+  virtual void Seek(base::TimeDelta time, const PipelineStatusCB& callback) = 0;

[scherkus (not reviewing), 2012/07/10 03:58:22]

think it's time to finally call this Preroll()? :)

[scherkus (not reviewing), 2012/07/17 03:43:00]

making it a TODO

+
+  // Stop all operations in preparation for being deleted, executing |callback|
+  // when complete.
+  virtual void Stop(const base::Closure& callback) = 0;
+
+  // Updates the current playback rate.
+  virtual void SetPlaybackRate(float playback_rate) = 0;
+
+  // Returns true if all audio data has been played back by the audio device.
   virtual bool HasEnded() = 0;
 
   // Sets the output volume.
   virtual void SetVolume(float volume) = 0;
 
   // Resumes playback after underflow occurs.
+  //
   // |buffer_more_audio| is set to true if you want to increase the size of the
   // decoded audio buffer.
   virtual void ResumeAfterUnderflow(bool buffer_more_audio) = 0;
 
  protected:
+  friend class base::RefCountedThreadSafe<AudioRenderer>;
   virtual ~AudioRenderer() {}
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_RENDERER_H_