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// 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_BASE_TIME_SOURCE_H_
#define MEDIA_BASE_TIME_SOURCE_H_
#include "base/time/time.h"
#include "media/base/media_export.h"
namespace media {
// A TimeSource is capable of providing the current media time.
class MEDIA_EXPORT TimeSource {
public:
TimeSource() {}
virtual ~TimeSource() {}
// Signal the time source to start ticking. It is expected that values from
// CurrentMediaTime() will start increasing.
virtual void StartTicking() = 0;
// Signal the time source to stop ticking. It is expected that values from
// CurrentMediaTime() will remain constant.
virtual void StopTicking() = 0;
// Updates the current playback rate. It is expected that values from
// CurrentMediaTime() will eventually reflect the new playback rate (e.g., the
// media time will advance at half speed if the rate was set to 0.5f).
virtual void SetPlaybackRate(float playback_rate) = 0;
// Sets the media time to start ticking from. Only valid to call while the
// time source is not ticking.
virtual void SetMediaTime(base::TimeDelta time) = 0;
// Returns the current media time.
//
// Values returned are intended for informational purposes, such as displaying
// UI with the current minute and second count. While it is guaranteed values
// will never go backwards, the frequency at which they update may be low.
virtual base::TimeDelta CurrentMediaTime() = 0;
// Returns the current media time for use with synchronizing video.
//
// Differences from CurrentMediaTime():
// - Values returned update at a much higher frequency (e.g., suitable for
// playback of 60 FPS content).
// - As a result, values may go slightly backwards depending on the
// implementation (e.g., uses interpolation).
//
// TODO(scherkus): Replace with a method that returns wall clock time for a
// given media time for use with VideoFrameScheduler http://crbug.com/110814
virtual base::TimeDelta CurrentMediaTimeForSyncingVideo() = 0;
};
} // namespace media
#endif // MEDIA_BASE_TIME_SOURCE_H_
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