media/base/wall_clock_time_source.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_BASE_WALL_CLOCK_TIME_SOURCE_H_
   6 #define MEDIA_BASE_WALL_CLOCK_TIME_SOURCE_H_
   7
   8 #include "base/memory/scoped_ptr.h"
   9 #include "base/synchronization/lock.h"
  10 #include "base/time/default_tick_clock.h"
  11 #include "media/base/media_export.h"
  12 #include "media/base/time_source.h"
  13
  14 namespace media {
  15
  16 // A time source that uses interpolation based on the system clock.
  17 class MEDIA_EXPORT WallClockTimeSource : public TimeSource {
  18  public:
  19   WallClockTimeSource();
  20   ~WallClockTimeSource() override;
  21
  22   // TimeSource implementation.
  23   void StartTicking() override;
  24   void StopTicking() override;
  25   void SetPlaybackRate(double playback_rate) override;
  26   void SetMediaTime(base::TimeDelta time) override;
  27   base::TimeDelta CurrentMediaTime() override;
  28   bool GetWallClockTimes(
  29       const std::vector<base::TimeDelta>& media_timestamps,
  30       std::vector<base::TimeTicks>* wall_clock_times) override;
  31
  32   void set_tick_clock_for_testing(base::TickClock* tick_clock) {
  33     tick_clock_ = tick_clock;
  34   }
  35
  36  private:
  37   base::TimeDelta CurrentMediaTime_Locked();
  38
  39   // Allow for an injectable tick clock for testing.
  40   base::DefaultTickClock default_tick_clock_;
  41
  42   // If specified, used instead of |default_tick_clock_|.
  43   base::TickClock* tick_clock_;
  44
  45   bool ticking_;
  46
  47   // While ticking we can interpolate the current media time by measuring the
  48   // delta between our reference ticks and the current system ticks and scaling
  49   // that time by the playback rate.
  50   double playback_rate_;
  51   base::TimeDelta base_timestamp_;
  52   base::TimeTicks reference_time_;
  53
  54   // TODO(scherkus): Remove internal locking from this class after access to
  55   // Renderer::CurrentMediaTime() is single threaded http://crbug.com/370634
  56   base::Lock lock_;
  57
  58   DISALLOW_COPY_AND_ASSIGN(WallClockTimeSource);
  59 };
  60
  61 }  // namespace media
  62
  63 #endif  // MEDIA_BASE_WALL_CLOCK_TIME_SOURCE_H_