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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 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().
// 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.
#include "base/macros.h"
#include "media/audio/audio_io.h"
#include "media/audio/audio_manager.h"
#include "media/base/audio_parameters.h"
namespace base {
class SingleThreadTaskRunner;
namespace media {
class AudioOutputProxy;
class MEDIA_EXPORT AudioOutputDispatcher {
AudioOutputDispatcher(AudioManager* audio_manager,
const AudioParameters& params,
const std::string& device_id);
virtual ~AudioOutputDispatcher();
// Creates an instance of AudioOutputProxy, which uses |this| as dispatcher.
// The client owns the returned pointer, which can be deleted using
// AudioOutputProxy::Close.
virtual AudioOutputProxy* CreateStreamProxy() = 0;
// Called by AudioOutputProxy to open the stream.
// 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;
// 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 volume is set.
virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
double volume) = 0;
// Called by AudioOutputProxy when the stream is closed.
virtual void CloseStream(AudioOutputProxy* stream_proxy) = 0;
const std::string& device_id() const { return device_id_; }
// A no-reference-held pointer (we don't want circular references) back to the
// AudioManager that owns this object.
AudioManager* audio_manager_;
const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
const AudioParameters params_;
std::string device_id_;
} // namespace media