Cast: Reshuffle files under media/cast

media/cast/base/clock_drift_smoother.h

-// 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_CAST_BASE_CLOCK_DRIFT_SMOOTHER_H_
-#define MEDIA_CAST_BASE_CLOCK_DRIFT_SMOOTHER_H_
-
-#include "base/time/time.h"
-
-namespace media {
-namespace cast {
-
-// Tracks the jitter and drift between clocks, providing a smoothed offset.
-// Internally, a Simple IIR filter is used to maintain a running average that
-// moves at a rate based on the passage of time.
-class ClockDriftSmoother {
- public:
-  // |time_constant| is the amount of time an impulse signal takes to decay by
-  // ~62.6%.  Interpretation: If the value passed to several Update() calls is
-  // held constant for T seconds, then the running average will have moved
-  // towards the value by ~62.6% from where it started.
-  explicit ClockDriftSmoother(base::TimeDelta time_constant);
-  ~ClockDriftSmoother();
-
-  // Returns the current offset.
-  base::TimeDelta Current() const;
-
-  // Discard all history and reset to exactly |offset|, measured |now|.
-  void Reset(base::TimeTicks now, base::TimeDelta offset);
-
-  // Update the current offset, which was measured |now|.  The weighting that
-  // |measured_offset| will have on the running average is influenced by how
-  // much time has passed since the last call to this method (or Reset()).
-  // |now| should be monotonically non-decreasing over successive calls of this
-  // method.
-  void Update(base::TimeTicks now, base::TimeDelta measured_offset);
-
-  // Returns a time constant suitable for most use cases, where the clocks
-  // are expected to drift very little with respect to each other, and the
-  // jitter caused by clock imprecision is effectively canceled out.
-  static base::TimeDelta GetDefaultTimeConstant();
-
- private:
-  const base::TimeDelta time_constant_;
-  base::TimeTicks last_update_time_;
-  double estimate_us_;
-};
-
-}  // namespace cast
-}  // namespace media
-
-#endif  // MEDIA_CAST_BASE_CLOCK_DRIFT_SMOOTHER_H_