Implementation of 'AudioContext.getOutputTimestamp' method

media/audio/audio_io.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.
 
 #ifndef MEDIA_AUDIO_AUDIO_IO_H_
 #define MEDIA_AUDIO_AUDIO_IO_H_
 
 #include <stdint.h>
 
 #include "media/base/audio_bus.h"
@@ skipping 31 matching lines @@
 // Because we support more audio streams than physically available channels
 // a given AudioOutputStream might or might not talk directly to hardware.
 // An audio stream allocates several buffers for audio data and calls
 // AudioSourceCallback::OnMoreData() periodically to fill these buffers,
 // as the data is written to the audio device. Size of each packet is determined
 // by |samples_per_packet| specified in AudioParameters  when the stream is
 // created.
 
 namespace media {
 
+struct MEDIA_EXPORT AudioTimestamp {
+  int64_t frames;
+  int64_t ticks;  // Obtained from base::TimeTicks::ToInternalValue().
+};
+
+// Used in unittests.
+inline bool operator==(const AudioTimestamp& one, const AudioTimestamp& other) {
+  return one.ticks == other.ticks && one.frames == other.frames;
+}
+
 class MEDIA_EXPORT AudioOutputStream {
  public:
   // Audio sources must implement AudioSourceCallback. This interface will be
   // called in a random thread which very likely is a high priority thread. Do
   // not rely on using this thread TLS or make calls that alter the thread
   // itself such as creating Windows or initializing COM.
   class MEDIA_EXPORT AudioSourceCallback {
    public:
     virtual ~AudioSourceCallback() {}
 
     // Provide more data by fully filling |dest|.  The source will return
     // the number of frames it filled.  |total_bytes_delay| contains current
     // number of bytes of delay buffered by the AudioOutputStream.
     // |frames_skipped| contains the number of frames skipped by the consumer.
+    // |timestamp| if provided, contains timestamp of the currently audible
+    // signal.
     virtual int OnMoreData(AudioBus* dest,
                            uint32_t total_bytes_delay,
-                           uint32_t frames_skipped) = 0;
+                           uint32_t frames_skipped,
+                           const AudioTimestamp& output_timestamp = {0, 0}) = 0;
 
     // There was an error while playing a buffer. Audio source cannot be
     // destroyed yet. No direct action needed by the AudioStream, but it is
     // a good place to stop accumulating sound data since is is likely that
     // playback will not continue.
     virtual void OnError(AudioOutputStream* stream) = 0;
   };
 
   virtual ~AudioOutputStream() {}
 
@@ skipping 89 matching lines @@
   // Returns the Automatic Gain Control (AGC) state.
   virtual bool GetAutomaticGainControl() = 0;
 
   // Returns the current muting state for the microphone.
   virtual bool IsMuted() = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_IO_H_