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// 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.
// 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().
//
// 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_manager.h"
#include "media/audio/audio_parameters.h"
class MessageLoop;
namespace media {
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,
base::TimeDelta close_delay);
~AudioOutputDispatcher();
// 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.
bool StreamOpened();
// 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 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.
void StreamClosed();
// Called on the audio thread when the AudioManager is shutting down.
void Shutdown();
private:
friend class AudioOutputProxyTest;
// 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.
AudioManager* audio_manager_;
MessageLoop* message_loop_;
AudioParameters params_;
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);
};
} // namespace media
#endif // MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
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