Introduce media::AudioClock::WallTimeForTimestamp().

media/filters/audio_clock.h

 // Copyright 2014 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_FILTERS_AUDIO_CLOCK_H_
 #define MEDIA_FILTERS_AUDIO_CLOCK_H_
 
 #include <deque>
 
 #include "base/time/time.h"
@@ skipping 66 matching lines @@
   base::TimeDelta front_timestamp() const { return front_timestamp_; }
   base::TimeDelta back_timestamp() const { return back_timestamp_; }
 
   // Clients can provide |time_since_writing| to simulate the passage of time
   // since last writing audio to get a more accurate current media timestamp.
   //
   // The value will be bounded between front_timestamp() and back_timestamp().
   base::TimeDelta TimestampSinceWriting(
       base::TimeDelta time_since_writing) const;
 
+  // Returns the amount of wall time until |timestamp| will be played by the
+  // audio hardware.
+  //
+  // |timestamp| must be within front_timestamp() and back_timestamp().
+  base::TimeDelta WallTimeForTimestamp(base::TimeDelta timestamp) const;

[DaleCurtis, 2014/09/20 00:17:12]

What do you think about TimeToPlayback(), TimeUntilAudible(), some variation
there of?  WallTimeForTimestamp just seems kind of obtuse and this class already
introduces some non-obvious concepts.

[scherkus (not reviewing), 2014/09/22 18:34:12]

picked TimeUntilPlayback()

+
   // Returns the amount of contiguous media time buffered at the head of the
   // audio hardware buffer. Silence introduced into the audio hardware buffer is
   // treated as a break in media time.
   base::TimeDelta contiguous_audio_data_buffered() const {
     return contiguous_audio_data_buffered_;
   }
 
   // Same as above, but also treats changes in playback rate as a break in media
   // time.
   base::TimeDelta contiguous_audio_data_buffered_at_same_rate() const {
@@ skipping 30 matching lines @@
   // Cached results of last call to WroteAudio().
   base::TimeDelta contiguous_audio_data_buffered_;
   base::TimeDelta contiguous_audio_data_buffered_at_same_rate_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioClock);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_AUDIO_CLOCK_H_