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      1 // Copyright 2014 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_FILTERS_AUDIO_CLOCK_H_
      6 #define MEDIA_FILTERS_AUDIO_CLOCK_H_
      7 
      8 #include <deque>
      9 
     10 #include "base/time/time.h"
     11 #include "media/base/media_export.h"
     12 
     13 namespace media {
     14 
     15 // Models a queue of buffered audio in a playback pipeline for use with
     16 // estimating the amount of delay in wall clock time. Takes changes in playback
     17 // rate into account to handle scenarios where multiple rates may be present in
     18 // a playback pipeline with large delay.
     19 class MEDIA_EXPORT AudioClock {
     20  public:
     21   explicit AudioClock(int sample_rate);
     22   ~AudioClock();
     23 
     24   // |frames| amount of audio data scaled to |playback_rate| was written.
     25   // |delay_frames| is the current amount of hardware delay.
     26   // |timestamp| is the endpoint media timestamp of the audio data written.
     27   void WroteAudio(int frames,
     28                   int delay_frames,
     29                   float playback_rate,
     30                   base::TimeDelta timestamp);
     31 
     32   // |frames| amount of silence was written.
     33   // |delay_frames| is the current amount of hardware delay.
     34   void WroteSilence(int frames, int delay_frames);
     35 
     36   // Calculates the current media timestamp taking silence and changes in
     37   // playback rate into account.
     38   base::TimeDelta CurrentMediaTimestamp() const;
     39 
     40   // Returns the last endpoint timestamp provided to WroteAudio().
     41   base::TimeDelta last_endpoint_timestamp() const {
     42     return last_endpoint_timestamp_;
     43   }
     44 
     45  private:
     46   void TrimBufferedAudioToMatchDelay(int delay_frames);
     47   void PushBufferedAudio(int frames,
     48                          float playback_rate,
     49                          base::TimeDelta endpoint_timestamp);
     50 
     51   const int sample_rate_;
     52 
     53   // Initially set to kNoTimestamp(), otherwise is the last endpoint timestamp
     54   // delivered to WroteAudio(). A copy is kept outside of |buffered_audio_| to
     55   // handle the case where all of |buffered_audio_| has been replaced with
     56   // silence.
     57   base::TimeDelta last_endpoint_timestamp_;
     58 
     59   struct BufferedAudio {
     60     BufferedAudio(int frames,
     61                   float playback_rate,
     62                   base::TimeDelta endpoint_timestamp);
     63 
     64     int frames;
     65     float playback_rate;
     66     base::TimeDelta endpoint_timestamp;
     67   };
     68 
     69   std::deque<BufferedAudio> buffered_audio_;
     70 
     71   DISALLOW_COPY_AND_ASSIGN(AudioClock);
     72 };
     73 
     74 }  // namespace media
     75 
     76 #endif  // MEDIA_FILTERS_AUDIO_CLOCK_H_
     77