Remove Mac input audio restart mechanism and reduce time until startup success check.

media/audio/mac/audio_low_latency_input_mac.h

 // 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.
 //
 // Implementation of AudioInputStream for Mac OS X using the special AUHAL
 // input Audio Unit present in OS 10.4 and later.
 // The AUHAL input Audio Unit is for low-latency audio I/O.
 //
 // Overview of operation:
 //
@@ skipping 112 matching lines @@
       const AudioObjectPropertyAddress addresses[],
       void* context);
   OSStatus DevicePropertyChanged(AudioObjectID object_id,
                                  UInt32 num_addresses,
                                  const AudioObjectPropertyAddress addresses[]);
 
   // Updates the |device_property_changes_map_| on the main browser thread,
   // (CrBrowserMain) which is the same thread as this instance is created on.
   void DevicePropertyChangedOnMainThread(const std::vector<UInt32>& properties);
 
-  // Updates |last_callback_time_| on the main browser thread.
-  void UpdateDataCallbackTimeOnMainThread(base::TimeTicks now_tick);
-
   // Registers OnDevicePropertyChanged() to receive notifications when device
   // properties changes.
   void RegisterDeviceChangeListener();
   // Stop listening for changes in device properties.
   void DeRegisterDeviceChangeListener();
 
   // Gets the fixed capture hardware latency and store it during initialization.
   // Returns 0 if not available.
   double GetHardwareLatency();
 
   // Gets the current capture delay value.
   double GetCaptureLatency(const AudioTimeStamp* input_time_stamp);
 
   // Gets the number of channels for a stream of audio data.
   int GetNumberOfChannelsFromStream();
 
   // Issues the OnError() callback to the |sink_|.
   void HandleError(OSStatus err);
 
   // Helper function to check if the volume control is avialable on specific
   // channel.
   bool IsVolumeSettableOnChannel(int channel);
 
   // Helper methods to set and get atomic |input_callback_is_active_|.
   void SetInputCallbackIsActive(bool active);
   bool GetInputCallbackIsActive();
 
   // Checks if a stream was started successfully and the audio unit also starts
   // to call InputProc() as it should. This method is called once when a timer
-  // expires 5 seconds after calling Start().
+  // expires some time after calling Start().
   void CheckInputStartupSuccess();
 
-  // Checks (periodically) if a stream is alive by comparing the current time
-  // with the last timestamp stored in a data callback. Calls RestartAudio()
-  // when a restart is required.
-  void CheckIfInputStreamIsAlive();
-
   // Uninitializes the audio unit if needed.
   void CloseAudioUnit();
 
-  // Called by CheckIfInputStreamIsAlive() on the main thread when an audio
-  // restarts is required. Restarts the existing audio stream reusing the
-  // current audio parameters.
-  void RestartAudio();
-
   // Adds extra UMA stats when it has been detected that startup failed.
   void AddHistogramsForFailedStartup();
 
   // Scans the map of all available property changes (notification types) and
   // filters out some that make sense to add to UMA stats.
   void AddDevicePropertyChangesToUMA(bool startup_failed);
 
   // Updates capture timestamp, current lost frames, and total lost frames and
   // glitches.
   void UpdateCaptureTimestamp(const AudioTimeStamp* timestamp);
@@ skipping 54 matching lines @@
 
   // Used to defer Start() to workaround http://crbug.com/160920.
   base::CancelableClosure deferred_start_cb_;
 
   // Contains time of last successful call to AudioUnitRender().
   // Initialized first time in Start() and then updated for each valid
   // audio buffer. Used to detect long error sequences and to take actions
   // if length of error sequence is above a certain limit.
   base::TimeTicks last_success_time_;
 
-  // Is set to true on the internal AUHAL IO thread in the first input callback
-  // after Start() has bee called.
+  // Flags to indicate if we have gotten an input callback.
+  // |got_input_callback_| is only accessed on the OS audio thread in
+  // OnDataIsAvailable() and is set to true when the first callback comes. It
+  // acts as a gate to only set |input_callback_is_active_| atomically once.
+  // |got_input_callback_| is reset to false in Stop() on the main thread. This
+  // is safe since after stopping the audio unit there is no current callback
+  // ongoing and no further callbacks coming.
+  bool got_input_callback_;
   base::subtle::Atomic32 input_callback_is_active_;
 
   // Timer which triggers CheckInputStartupSuccess() to verify that input
   // callbacks have started as intended after a successful call to Start().
   // This timer lives on the main browser thread.
   std::unique_ptr<base::OneShotTimer> input_callback_timer_;
 
   // Set to true if the Start() call was delayed.
   // See AudioManagerMac::ShouldDeferStreamStart() for details.
   bool start_was_deferred_;
@@ skipping 27 matching lines @@
   // callback audio thread.
   // These variables are only touched on the callback thread and then read
   // in the dtor (when no longer receiving callbacks).
   // NOTE: Float64 and UInt32 types are used for native API compatibility.
   Float64 last_sample_time_;
   UInt32 last_number_of_frames_;
   UInt32 total_lost_frames_;
   UInt32 largest_glitch_frames_;
   int glitches_detected_;
 
-  // Timer that provides periodic callbacks used to monitor if the input stream
-  // is alive or not.
-  std::unique_ptr<base::RepeatingTimer> check_alive_timer_;
-
-  // Time tick set once in each input data callback. The time is measured on
-  // the real-time priority I/O thread but this member is modified and read
-  // on the main thread only.
-  base::TimeTicks last_callback_time_;
-
-  // Counts number of times we get a signal of that a restart seems required.
-  // If it is above a threshold (kNumberOfIndicationsToTriggerRestart), the
-  // current audio stream is closed and a new (using same audio parameters) is
-  // started.
-  size_t number_of_restart_indications_;
-
-  // Counts number of times RestartAudio() has been called. The max number of
-  // attempts is restricted by |kMaxNumberOfRestartAttempts|.
-  // Note that this counter is reset to zero after each successful restart.
-  size_t number_of_restart_attempts_;
-
-  // Counts the total number of times RestartAudio() has been called. It is
-  // set to zero once in the constructor and then never reset again.
-  size_t total_number_of_restart_attempts_;
-
   // Callback to send statistics info.
   AudioManager::LogCallback log_callback_;
 
   // Used to ensure DevicePropertyChangedOnMainThread() is not called when
   // this object is destroyed.
   // Note that, all member variables should appear before the WeakPtrFactory.
   base::WeakPtrFactory<AUAudioInputStream> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AUAudioInputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_