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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_DELTA_INTERPOLATOR_H_
- #define MEDIA_BASE_TIME_DELTA_INTERPOLATOR_H_
- #include "base/memory/raw_ptr.h"
- #include "base/time/time.h"
- #include "media/base/media_export.h"
- namespace base {
- class TickClock;
- } // namespace base
- namespace media {
- // Interpolates between two TimeDeltas based on the passage of wall clock time
- // and the current playback rate.
- //
- // TimeDeltaInterpolator is not thread-safe and must be externally locked.
- class MEDIA_EXPORT TimeDeltaInterpolator {
- public:
- // Constructs an interpolator initialized to zero with a rate of 1.0.
- //
- // |tick_clock| is used for sampling wall clock time for interpolating.
- explicit TimeDeltaInterpolator(const base::TickClock* tick_clock);
- TimeDeltaInterpolator(const TimeDeltaInterpolator&) = delete;
- TimeDeltaInterpolator& operator=(const TimeDeltaInterpolator&) = delete;
- ~TimeDeltaInterpolator();
- bool interpolating() { return interpolating_; }
- // Starts returning interpolated TimeDelta values.
- //
- // |tick_clock| will be queried for a new reference time value.
- base::TimeDelta StartInterpolating();
- // Stops returning interpolated TimeDelta values.
- //
- // |tick_clock| will be queried for a new reference time value.
- base::TimeDelta StopInterpolating();
- // Sets a new rate at which to interpolate.
- // The default rate is 0.
- //
- // |tick_clock| will be queried for a new reference time value.
- void SetPlaybackRate(double playback_rate);
- // Sets the two timestamps to interpolate between at |playback_rate_|.
- // |upper_bound| must be greater or equal to |lower_bound|.
- //
- // |upper_bound| is typically the media timestamp of the last audio frame
- // buffered by the audio hardware.
- void SetBounds(base::TimeDelta lower_bound,
- base::TimeDelta upper_bound,
- base::TimeTicks capture_time);
- // Sets the upper bound used for interpolation. Note that if |upper_bound| is
- // less than what was previously set via SetTime(), then all future calls
- // to GetInterpolatedTime() will return |upper_bound|.
- void SetUpperBound(base::TimeDelta upper_bound);
- // Computes an interpolated time based on SetTime().
- base::TimeDelta GetInterpolatedTime();
- private:
- const raw_ptr<const base::TickClock> tick_clock_;
- bool interpolating_;
- // The range of time to interpolate between.
- base::TimeDelta lower_bound_;
- base::TimeDelta upper_bound_;
- // The monotonic system clock time used for interpolating between
- // |lower_bound_| and |upper_bound_|.
- base::TimeTicks reference_;
- double playback_rate_;
- };
- } // namespace media
- #endif // MEDIA_BASE_TIME_DELTA_INTERPOLATOR_H_
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