media/audio/audio_output_controller.h

   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.
   4
   5 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
   6 #define MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
   7
   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"
  19
  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.
  24 //
  25 // All the public methods of AudioOutputController are non-blocking.
  26 // The actual operations are performed on the audio manager thread.
  27 //
  28 // Here is a state transition diagram for the AudioOutputController:
  29 //
  30 //   *[ Empty ]  -->  [ Created ]  -->  [ Playing ]  -------.
  31 //        |                |               |    ^           |
  32 //        |                |               |    |           |
  33 //        |                |               |    |           v
  34 //        |                |               |    `-----  [ Paused ]
  35 //        |                |               |                |
  36 //        |                v               v                |
  37 //        `----------->  [      Closed       ]  <-----------'
  38 //
  39 // * Initial state
  40 //
  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
  47 // state.
  48 //
  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.
  52 //
  53
  54 namespace media {
  55
  56 class MEDIA_EXPORT AudioOutputController
  57     : public base::RefCountedThreadSafe<AudioOutputController>,
  58       public AudioOutputStream::AudioSourceCallback,
  59       public AudioSourceDiverter,
  60       NON_EXPORTED_BASE(public AudioManager::AudioDeviceListener)  {
  61  public:
  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 {
  65    public:
  66     virtual void OnCreated() = 0;
  67     virtual void OnPlaying() = 0;
  68     virtual void OnPaused() = 0;
  69     virtual void OnError() = 0;
  70
  71    protected:
  72     virtual ~EventHandler() {}
  73   };
  74
  75   // A synchronous reader interface used by AudioOutputController for
  76   // synchronous reading.
  77   // TODO(crogers): find a better name for this class and the Read() method
  78   // now that it can handle synchronized I/O.
  79   class SyncReader {
  80    public:
  81     virtual ~SyncReader() {}
  82
  83     // Notify the synchronous reader the number of bytes in the
  84     // AudioOutputController not yet played. This is used by SyncReader to
  85     // prepare more data and perform synchronization.
  86     virtual void UpdatePendingBytes(uint32 bytes) = 0;
  87
  88     // Attempts to completely fill |dest|, zeroing |dest| if the request can not
  89     // be fulfilled (due to timeout).
  90     virtual void Read(AudioBus* dest) = 0;
  91
  92     // Close this synchronous reader.
  93     virtual void Close() = 0;
  94   };
  95
  96   // Factory method for creating an AudioOutputController.
  97   // This also creates and opens an AudioOutputStream on the audio manager
  98   // thread, and if this is successful, the |event_handler| will receive an
  99   // OnCreated() call from the same audio manager thread.  |audio_manager| must
 100   // outlive AudioOutputController.
 101   // The |output_device_id| can be either empty (default device) or specify a
 102   // specific hardware device for audio output.
 103   static scoped_refptr<AudioOutputController> Create(
 104       AudioManager* audio_manager, EventHandler* event_handler,
 105       const AudioParameters& params, const std::string& output_device_id,
 106       SyncReader* sync_reader);
 107
 108   // Indicates whether audio power level analysis will be performed.  If false,
 109   // ReadCurrentPowerAndClip() can not be called.
 110   static bool will_monitor_audio_levels() {
 111 #if defined(OS_ANDROID) || defined(OS_IOS)
 112     return false;
 113 #else
 114     return true;
 115 #endif
 116   }
 117
 118   // Methods to control playback of the stream.
 119
 120   // Starts the playback of this audio output stream.
 121   void Play();
 122
 123   // Pause this audio output stream.
 124   void Pause();
 125
 126   // Closes the audio output stream. The state is changed and the resources
 127   // are freed on the audio manager thread. closed_task is executed after that.
 128   // Callbacks (EventHandler and SyncReader) must exist until closed_task is
 129   // called.
 130   //
 131   // It is safe to call this method more than once. Calls after the first one
 132   // will have no effect.
 133   void Close(const base::Closure& closed_task);
 134
 135   // Sets the volume of the audio output stream.
 136   void SetVolume(double volume);
 137
 138   // Calls |callback| (on the caller's thread) with the current output
 139   // device ID.
 140   void GetOutputDeviceId(
 141       base::Callback<void(const std::string&)> callback) const;
 142
 143   // Changes which output device to use. If desired, you can provide a
 144   // callback that will be notified (on the thread you called from)
 145   // when the function has completed execution.
 146   //
 147   // Changing the output device causes the controller to go through
 148   // the same state transition back to the current state as a call to
 149   // OnDeviceChange (unless it is currently diverting, see
 150   // Start/StopDiverting below, in which case the state transition
 151   // will happen when StopDiverting is called).
 152   void SwitchOutputDevice(const std::string& output_device_id,
 153                           const base::Closure& callback);
 154
 155   // AudioSourceCallback implementation.
 156   int OnMoreData(AudioBus* dest, uint32 total_bytes_delay) override;
 157   void OnError(AudioOutputStream* stream) override;
 158
 159   // AudioDeviceListener implementation.  When called AudioOutputController will
 160   // shutdown the existing |stream_|, transition to the kRecreating state,
 161   // create a new stream, and then transition back to an equivalent state prior
 162   // to being called.
 163   void OnDeviceChange() override;
 164
 165   // AudioSourceDiverter implementation.
 166   const AudioParameters& GetAudioParameters() override;
 167   void StartDiverting(AudioOutputStream* to_stream) override;
 168   void StopDiverting() override;
 169
 170   // Accessor for AudioPowerMonitor::ReadCurrentPowerAndClip().  See comments in
 171   // audio_power_monitor.h for usage.  This may be called on any thread.
 172   std::pair<float, bool> ReadCurrentPowerAndClip();
 173
 174  protected:
 175   // Internal state of the source.
 176   enum State {
 177     kEmpty,
 178     kCreated,
 179     kPlaying,
 180     kPaused,
 181     kClosed,
 182     kError,
 183   };
 184
 185   // Time constant for AudioPowerMonitor.  See AudioPowerMonitor ctor comments
 186   // for semantics.  This value was arbitrarily chosen, but seems to work well.
 187   enum { kPowerMeasurementTimeConstantMillis = 10 };
 188
 189   friend class base::RefCountedThreadSafe<AudioOutputController>;
 190   ~AudioOutputController() override;
 191
 192  private:
 193   AudioOutputController(AudioManager* audio_manager, EventHandler* handler,
 194                         const AudioParameters& params,
 195                         const std::string& output_device_id,
 196                         SyncReader* sync_reader);
 197
 198   // The following methods are executed on the audio manager thread.
 199   void DoCreate(bool is_for_device_change);
 200   void DoPlay();
 201   void DoPause();
 202   void DoClose();
 203   void DoSetVolume(double volume);
 204   std::string DoGetOutputDeviceId() const;
 205   void DoSwitchOutputDevice(const std::string& output_device_id);
 206   void DoReportError();
 207   void DoStartDiverting(AudioOutputStream* to_stream);
 208   void DoStopDiverting();
 209
 210   // Helper method that stops the physical stream.
 211   void StopStream();
 212
 213   // Helper method that stops, closes, and NULLs |*stream_|.
 214   void DoStopCloseAndClearStream();
 215
 216   // Checks if a stream was started successfully but never calls OnMoreData().
 217   void WedgeCheck();
 218
 219   AudioManager* const audio_manager_;
 220   const AudioParameters params_;
 221   EventHandler* const handler_;
 222
 223   // Specifies the device id of the output device to open or empty for the
 224   // default output device.
 225   std::string output_device_id_;
 226
 227   AudioOutputStream* stream_;
 228
 229   // When non-NULL, audio is being diverted to this stream.
 230   AudioOutputStream* diverting_to_stream_;
 231
 232   // The current volume of the audio stream.
 233   double volume_;
 234
 235   // |state_| is written on the audio manager thread and is read on the
 236   // hardware audio thread. These operations need to be locked. But lock
 237   // is not required for reading on the audio manager thread.
 238   State state_;
 239
 240   // SyncReader is used only in low latency mode for synchronous reading.
 241   SyncReader* const sync_reader_;
 242
 243   // The message loop of audio manager thread that this object runs on.
 244   const scoped_refptr<base::SingleThreadTaskRunner> message_loop_;
 245
 246   // Scans audio samples from OnMoreData() as input to compute power levels.
 247   AudioPowerMonitor power_monitor_;
 248
 249   // Flags when we've asked for a stream to start but it never did.
 250   base::AtomicRefCount on_more_io_data_called_;
 251   scoped_ptr<base::OneShotTimer<AudioOutputController> > wedge_timer_;
 252
 253   DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
 254 };
 255
 256 }  // namespace media
 257
 258 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_