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 "media/base/media_export.h"
  11 #include "media/base/time_source.h"
  12
  13 namespace base {
  14 class TickClock;
  15 }
  16
  17 namespace media {
  18
  19 // A time source that uses interpolation based on the system clock.
  20 class MEDIA_EXPORT WallClockTimeSource : public TimeSource {
  21  public:
  22   WallClockTimeSource();
  23   ~WallClockTimeSource() override;
  24
  25   // TimeSource implementation.
  26   void StartTicking() override;
  27   void StopTicking() override;
  28   void SetPlaybackRate(float playback_rate) override;
  29   void SetMediaTime(base::TimeDelta time) override;
  30   base::TimeDelta CurrentMediaTime() override;
  31   base::TimeDelta CurrentMediaTimeForSyncingVideo() override;
  32
  33   void SetTickClockForTesting(scoped_ptr<base::TickClock> tick_clock);
  34
  35  private:
  36   base::TimeDelta CurrentMediaTime_Locked();
  37
  38   scoped_ptr<base::TickClock> tick_clock_;
  39   bool ticking_;
  40
  41   // While ticking we can interpolate the current media time by measuring the
  42   // delta between our reference ticks and the current system ticks and scaling
  43   // that time by the playback rate.
  44   float playback_rate_;
  45   base::TimeDelta base_time_;
  46   base::TimeTicks reference_wall_ticks_;
  47
  48   // TODO(scherkus): Remove internal locking from this class after access to
  49   // Renderer::CurrentMediaTime() is single threaded http://crbug.com/370634
  50   base::Lock lock_;
  51
  52   DISALLOW_COPY_AND_ASSIGN(WallClockTimeSource);
  53 };
  54
  55 }  // namespace media
  56
  57 #endif  // MEDIA_BASE_WALL_CLOCK_TIME_SOURCE_H_