media/filters/audio_clock.h

   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_