1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
6 #define MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
8 #include "base/atomic_ref_count.h"
9 #include "base/callback.h"
10 #include "base/memory/ref_counted.h"
11 #include "base/timer/timer.h"
12 #include "build/build_config.h"
13 #include "media/audio/audio_io.h"
14 #include "media/audio/audio_manager.h"
15 #include "media/audio/audio_power_monitor.h"
16 #include "media/audio/audio_source_diverter.h"
17 #include "media/audio/simple_sources.h"
18 #include "media/base/media_export.h"
20 // An AudioOutputController controls an AudioOutputStream and provides data
21 // to this output stream. It has an important function that it executes
22 // audio operations like play, pause, stop, etc. on a separate thread,
23 // namely the audio manager thread.
25 // All the public methods of AudioOutputController are non-blocking.
26 // The actual operations are performed on the audio manager thread.
28 // Here is a state transition diagram for the AudioOutputController:
30 // *[ Empty ] --> [ Created ] --> [ Playing ] -------.
34 // | | | `----- [ Paused ]
37 // `-----------> [ Closed ] <-----------'
41 // At any time after reaching the Created state but before Closed, the
42 // AudioOutputController may be notified of a device change via
43 // OnDeviceChange(). As the OnDeviceChange() is processed, state transitions
44 // will occur, ultimately ending up in an equivalent pre-call state. E.g., if
45 // the state was Paused, the new state will be Created, since these states are
46 // all functionally equivalent and require a Play() call to continue to the next
49 // The AudioOutputStream can request data from the AudioOutputController via the
50 // AudioSourceCallback interface. AudioOutputController uses the SyncReader
51 // passed to it via construction to synchronously fulfill this read request.
56 class MEDIA_EXPORT AudioOutputController
57 : public base::RefCountedThreadSafe<AudioOutputController>,
58 public AudioOutputStream::AudioSourceCallback,
59 public AudioSourceDiverter,
60 NON_EXPORTED_BASE(public AudioManager::AudioDeviceListener) {
62 // An event handler that receives events from the AudioOutputController. The
63 // following methods are called on the audio manager thread.
64 class MEDIA_EXPORT EventHandler {
66 virtual void OnCreated() = 0;
67 virtual void OnPlaying() = 0;
68 virtual void OnPaused() = 0;
69 virtual void OnError() = 0;
70 virtual void OnDeviceChange(int new_buffer_size, int new_sample_rate) = 0;
73 virtual ~EventHandler() {}
76 // A synchronous reader interface used by AudioOutputController for
77 // synchronous reading.
78 // TODO(crogers): find a better name for this class and the Read() method
79 // now that it can handle synchronized I/O.
82 virtual ~SyncReader() {}
84 // Notify the synchronous reader the number of bytes in the
85 // AudioOutputController not yet played. This is used by SyncReader to
86 // prepare more data and perform synchronization.
87 virtual void UpdatePendingBytes(uint32 bytes) = 0;
89 // Attempts to completely fill |dest|, zeroing |dest| if the request can not
90 // be fulfilled (due to timeout).
91 virtual void Read(AudioBus* dest) = 0;
93 // Close this synchronous reader.
94 virtual void Close() = 0;
97 // Factory method for creating an AudioOutputController.
98 // This also creates and opens an AudioOutputStream on the audio manager
99 // thread, and if this is successful, the |event_handler| will receive an
100 // OnCreated() call from the same audio manager thread. |audio_manager| must
101 // outlive AudioOutputController.
102 // The |output_device_id| can be either empty (default device) or specify a
103 // specific hardware device for audio output.
104 static scoped_refptr<AudioOutputController> Create(
105 AudioManager* audio_manager, EventHandler* event_handler,
106 const AudioParameters& params, const std::string& output_device_id,
107 SyncReader* sync_reader);
109 // Indicates whether audio power level analysis will be performed. If false,
110 // ReadCurrentPowerAndClip() can not be called.
111 static bool will_monitor_audio_levels() {
112 #if defined(OS_ANDROID) || defined(OS_IOS)
119 // Methods to control playback of the stream.
121 // Starts the playback of this audio output stream.
124 // Pause this audio output stream.
127 // Closes the audio output stream. The state is changed and the resources
128 // are freed on the audio manager thread. closed_task is executed after that.
129 // Callbacks (EventHandler and SyncReader) must exist until closed_task is
132 // It is safe to call this method more than once. Calls after the first one
133 // will have no effect.
134 void Close(const base::Closure& closed_task);
136 // Sets the volume of the audio output stream.
137 void SetVolume(double volume);
139 // Calls |callback| (on the caller's thread) with the current output
141 void GetOutputDeviceId(
142 base::Callback<void(const std::string&)> callback) const;
144 // Changes which output device to use. If desired, you can provide a
145 // callback that will be notified (on the thread you called from)
146 // when the function has completed execution.
148 // Changing the output device causes the controller to go through
149 // the same state transition back to the current state as a call to
150 // OnDeviceChange (unless it is currently diverting, see
151 // Start/StopDiverting below, in which case the state transition
152 // will happen when StopDiverting is called).
153 void SwitchOutputDevice(const std::string& output_device_id,
154 const base::Closure& callback);
156 // AudioSourceCallback implementation.
157 virtual int OnMoreData(AudioBus* dest,
158 AudioBuffersState buffers_state) OVERRIDE;
159 virtual void OnError(AudioOutputStream* stream) OVERRIDE;
161 // AudioDeviceListener implementation. When called AudioOutputController will
162 // shutdown the existing |stream_|, transition to the kRecreating state,
163 // create a new stream, and then transition back to an equivalent state prior
165 virtual void OnDeviceChange() OVERRIDE;
167 // AudioSourceDiverter implementation.
168 virtual const AudioParameters& GetAudioParameters() OVERRIDE;
169 virtual void StartDiverting(AudioOutputStream* to_stream) OVERRIDE;
170 virtual void StopDiverting() OVERRIDE;
172 // Accessor for AudioPowerMonitor::ReadCurrentPowerAndClip(). See comments in
173 // audio_power_monitor.h for usage. This may be called on any thread.
174 std::pair<float, bool> ReadCurrentPowerAndClip();
177 // Internal state of the source.
187 // Time constant for AudioPowerMonitor. See AudioPowerMonitor ctor comments
188 // for semantics. This value was arbitrarily chosen, but seems to work well.
189 enum { kPowerMeasurementTimeConstantMillis = 10 };
191 friend class base::RefCountedThreadSafe<AudioOutputController>;
192 virtual ~AudioOutputController();
195 AudioOutputController(AudioManager* audio_manager, EventHandler* handler,
196 const AudioParameters& params,
197 const std::string& output_device_id,
198 SyncReader* sync_reader);
200 // The following methods are executed on the audio manager thread.
201 void DoCreate(bool is_for_device_change);
205 void DoSetVolume(double volume);
206 std::string DoGetOutputDeviceId() const;
207 void DoSwitchOutputDevice(const std::string& output_device_id);
208 void DoReportError();
209 void DoStartDiverting(AudioOutputStream* to_stream);
210 void DoStopDiverting();
212 // Helper method that stops the physical stream.
215 // Helper method that stops, closes, and NULLs |*stream_|.
216 void DoStopCloseAndClearStream();
218 // Checks if a stream was started successfully but never calls OnMoreData().
221 AudioManager* const audio_manager_;
222 const AudioParameters params_;
223 EventHandler* const handler_;
225 // Specifies the device id of the output device to open or empty for the
226 // default output device.
227 std::string output_device_id_;
229 AudioOutputStream* stream_;
231 // When non-NULL, audio is being diverted to this stream.
232 AudioOutputStream* diverting_to_stream_;
234 // The current volume of the audio stream.
237 // |state_| is written on the audio manager thread and is read on the
238 // hardware audio thread. These operations need to be locked. But lock
239 // is not required for reading on the audio manager thread.
242 // SyncReader is used only in low latency mode for synchronous reading.
243 SyncReader* const sync_reader_;
245 // The message loop of audio manager thread that this object runs on.
246 const scoped_refptr<base::SingleThreadTaskRunner> message_loop_;
248 // Scans audio samples from OnMoreData() as input to compute power levels.
249 AudioPowerMonitor power_monitor_;
251 // Flags when we've asked for a stream to start but it never did.
252 base::AtomicRefCount on_more_io_data_called_;
253 scoped_ptr<base::OneShotTimer<AudioOutputController> > wedge_timer_;
255 DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
260 #endif // MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_