Revert 132891 - Software audio mixer.

Code goes through old or new paths depending on the AudioParameters or command-line flag.
Added unit tests.

Review URL: http://codereview.chromium.org/9691001

TBR=enal@chromium.org
Review URL: https://chromiumcodereview.appspot.com/10127002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@132929 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 69 insertions, 36 deletions

diff --git a/media/audio/audio_output_dispatcher.h b/media/audio/audio_output_dispatcher.h
index 5c96873..79474a4 100644
--- a/media/audio/audio_output_dispatcher.h
+++ b/media/audio/audio_output_dispatcher.h
@@ -2,26 +2,33 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// AudioOutputDispatcher is a single-threaded base class that dispatches
-// creation and deletion of audio output streams. AudioOutputProxy objects use
-// this class to allocate and recycle actual audio output streams. When playback
-// is started, the proxy calls StartStream() to get an output stream that it
-// uses to play audio. When playback is stopped, the proxy returns the stream
-// back to the dispatcher by calling StopStream().
+// AudioOutputDispatcher is a single-threaded class that dispatches creation and
+// deletion of audio output streams. AudioOutputProxy objects use this class to
+// allocate and recycle actual audio output streams. When playback is started,
+// the proxy calls StreamStarted() to get an output stream that it uses to play
+// audio. When playback is stopped, the proxy returns the stream back to the
+// dispatcher by calling StreamStopped().
 //
-// AudioManagerBase creates one specialization of AudioOutputDispatcher on the
-// audio thread for each possible set of audio parameters. I.e streams with
-// different parameters are managed independently.  The AudioOutputDispatcher
-// instance is then deleted on the audio thread when the AudioManager shuts
-// down.
+// To avoid opening and closing audio devices more frequently than necessary,
+// each dispatcher has a pool of inactive physical streams. A stream is closed
+// only if it hasn't been used for a certain period of time (specified via the
+// constructor).
+//
+// AudioManagerBase creates one AudioOutputDispatcher on the audio thread for
+// each possible set of audio parameters. I.e streams with different parameters
+// are managed independently.  The AudioOutputDispatcher instance is then
+// deleted on the audio thread when the AudioManager shuts down.
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
 
+#include <vector>
+#include <list>
+
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/timer.h"
-#include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
 #include "media/audio/audio_parameters.h"
 
@@ -29,43 +36,60 @@ class MessageLoop;
 
 namespace media {
 
-class AudioOutputProxy;
+class AudioOutputStream;
 
 class MEDIA_EXPORT AudioOutputDispatcher
     : public base::RefCountedThreadSafe<AudioOutputDispatcher> {
  public:
+  // |close_delay_ms| specifies delay after the stream is paused until
+  // the audio device is closed.
   AudioOutputDispatcher(AudioManager* audio_manager,
-                        const AudioParameters& params);
+                        const AudioParameters& params,
+                        base::TimeDelta close_delay);
+  ~AudioOutputDispatcher();
 
-  // Called by AudioOutputProxy to open the stream.
+  // Called by AudioOutputProxy when the stream is closed. Opens a new
+  // physical stream if there are no pending streams in |idle_streams_|.
   // Returns false, if it fails to open it.
-  virtual bool OpenStream() = 0;
-
-  // Called by AudioOutputProxy when the stream is started.
-  // Uses |callback| to get source data and report errors, if any.
-  // Does *not* take ownership of this callback.
-  // Returns true if started successfully, false otherwise.
-  virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
-                           AudioOutputProxy* stream_proxy) = 0;
+  bool StreamOpened();
 
-  // Called by AudioOutputProxy when the stream is stopped.
-  // Ownership of the |stream_proxy| is passed to the dispatcher.
-  virtual void StopStream(AudioOutputProxy* stream_proxy) = 0;
+  // Called by AudioOutputProxy when the stream is started. If there
+  // are pending streams in |idle_streams_| then it returns one of them,
+  // otherwise creates a new one. Returns a physical stream that must
+  // be used, or NULL if it fails to open audio device. Ownership of
+  // the result is passed to the caller.
+  AudioOutputStream* StreamStarted();
 
-
-  // Called by AudioOutputProxy when the volume is set.
-  virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
-                               double volume) = 0;
+  // Called by AudioOutputProxy when the stream is stopped.  Holds the
+  // stream temporarily in |pausing_streams_| and then |stream| is
+  // added to the pool of pending streams (i.e. |idle_streams_|).
+  // Ownership of the |stream| is passed to the dispatcher.
+  void StreamStopped(AudioOutputStream* stream);
 
   // Called by AudioOutputProxy when the stream is closed.
-  virtual void CloseStream(AudioOutputProxy* stream_proxy) = 0;
+  void StreamClosed();
 
   // Called on the audio thread when the AudioManager is shutting down.
-  virtual void Shutdown() = 0;
+  void Shutdown();
+
+ private:
+  friend class AudioOutputProxyTest;
 
- protected:
-  friend class base::RefCountedThreadSafe<AudioOutputDispatcher>;
-  virtual ~AudioOutputDispatcher();
+  // Creates a new physical output stream, opens it and pushes to
+  // |idle_streams_|.  Returns false if the stream couldn't be created or
+  // opened.
+  bool CreateAndOpenStream();
+
+  // A task scheduled by StreamStarted(). Opens a new stream and puts
+  // it in |idle_streams_|.
+  void OpenTask();
+
+  // Before a stream is reused, it should sit idle for a bit.  This task is
+  // called once that time has elapsed.
+  void StopStreamTask();
+
+  // Called by |close_timer_|. Closes all pending stream.
+  void ClosePendingStreams();
 
   // A no-reference-held pointer (we don't want circular references) back to the
   // AudioManager that owns this object.
@@ -73,7 +97,16 @@ class MEDIA_EXPORT AudioOutputDispatcher
   MessageLoop* message_loop_;
   AudioParameters params_;
 
- private:
+  base::TimeDelta pause_delay_;
+  size_t paused_proxies_;
+  typedef std::list<AudioOutputStream*> AudioOutputStreamList;
+  AudioOutputStreamList idle_streams_;
+  AudioOutputStreamList pausing_streams_;
+
+  // Used to post delayed tasks to ourselves that we cancel inside Shutdown().
+  base::WeakPtrFactory<AudioOutputDispatcher> weak_this_;
+  base::DelayTimer<AudioOutputDispatcher> close_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDispatcher);
 };