Implementation of 'AudioContext.getOutputTimestamp' method

third_party/WebKit/Source/platform/audio/AudioDestination.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 64 matching lines @@
 
   virtual void start();
   virtual void stop();
   bool isPlaying() { return m_isPlaying; }
 
   float sampleRate() const { return m_sampleRate; }
 
   // WebAudioDevice::RenderCallback
   void render(const WebVector<float*>& sourceData,
               const WebVector<float*>& audioData,
-              size_t numberOfFrames) override;
+              size_t numberOfFrames,
+              double delay,           // Output delay in seconds.

[miu, 2016/11/29 20:51:04]

suggestion: Just in case others get confused the way I did: Could you write a
method comment like: "|delay| and |delayTimestamp| are high-precision
measurements of the state of the system in the recent past. To be clear, |delay|
does *not* represent the point-in-time at which the first rendered sample will
be played out."

[miu, 2016/12/01 05:33:17]

Didn't see this addressed in PS10 (and looks like the extra code comments should
go in 	third_party/WebKit/public/platform/WebAudioDevice.h).

[Mikhail, 2016/12/02 11:48:21]

Done. Thanks for suggestion!

+              double delayTimestamp,  // System timestamp in seconds when
+                                      // |delay| was obtained.
+              size_t priorFramesSkipped) override;
 
   // AudioSourceProvider
   void provideInput(AudioBus*, size_t framesToProcess) override;
 
   static float hardwareSampleRate();
 
   // maxChannelCount() returns the total number of output channels of the audio
   // hardware.  A value of 0 indicates that the number of channels cannot be
   // configured and that only stereo (2-channel) destinations can be created.
   // The numberOfOutputChannels parameter of AudioDestination::create() is
   // allowed to be a value: 1 <= numberOfOutputChannels <= maxChannelCount(),
   // or if maxChannelCount() equals 0, then numberOfOutputChannels must be 2.
   static unsigned long maxChannelCount();
 
  private:
   AudioIOCallback& m_callback;
   unsigned m_numberOfOutputChannels;
   RefPtr<AudioBus> m_inputBus;
   RefPtr<AudioBus> m_renderBus;
   float m_sampleRate;
   bool m_isPlaying;
   std::unique_ptr<WebAudioDevice> m_audioDevice;
   size_t m_callbackBufferSize;
 
   std::unique_ptr<AudioFIFO> m_inputFifo;
   std::unique_ptr<AudioPullFIFO> m_fifo;
+
+  size_t m_framesElapsed;
+  AudioIOPosition m_outputPosition;
+  base::TimeTicks m_outputPositionReceivedTimestamp;
 };
 
 }  // namespace blink
 
 #endif  // AudioDestination_h