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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CC_TREES_FRAME_RATE_ESTIMATOR_H_
#define CC_TREES_FRAME_RATE_ESTIMATOR_H_
#include <cstdint>
#include "base/task/sequenced_task_runner.h"
#include "base/task/single_thread_task_runner.h"
#include "base/time/time.h"
#include "cc/base/delayed_unique_notifier.h"
#include "cc/cc_export.h"
namespace cc {
// The class is used to decide the preferred begin frame rate which related
// compositor frame sink should send based on video conference mode,
// NotifyInputEvent, WillDraw and DidNotProduceFrame. It will enter
// InputPriorityMode in the next 250ms(kInputPriorityDelay) if
// NotifyInputEvent() is called and exit after the delay. Throttling is
// disabled in InputPriorityMode despite other conditions.
// * In video conference mode:
// The frame rate will be throttled to half of the default when：
// Video conference mode is set and
// the last drawn consecutive_frames_with_min_delta_ <
// 4(kMinNumOfFramesWithMinDelta).
// The throttling will be stopped when:
// Video conference mode is unset or
// the last drawn consecutive_frames_with_min_delta_ >= 4.
class CC_EXPORT FrameRateEstimator {
public:
explicit FrameRateEstimator(base::SequencedTaskRunner* task_runner);
~FrameRateEstimator();
void SetVideoConferenceMode(bool enabled);
void WillDraw(base::TimeTicks now);
void NotifyInputEvent();
base::TimeDelta GetPreferredInterval() const;
bool input_priority_mode() const { return input_priority_mode_; }
void DidNotProduceFrame();
private:
void OnExitInputPriorityMode();
// Whether videoconference mode is enabled. In this mode, frame rate is
// reduced when there is no recent input and many frames with a small
// interval were produced.
bool in_video_conference_mode_ = false;
// Time of the last draw while in videoconference mode. Reset when exiting
// videoconference mode.
base::TimeTicks last_draw_time_in_video_conference_mode_;
// Number of consecutive frames drawn in videoconference mode with an interval
// lower than twice the default interval.
uint64_t num_of_consecutive_frames_with_min_delta_ = 0u;
// We conservatively switch to high frame rate after an input event to lower
// the input latency for a minimum duration. This tracks when we are in this
// mode.
bool input_priority_mode_ = false;
DelayedUniqueNotifier notifier_;
};
} // namespace cc
#endif // CC_TREES_FRAME_RATE_ESTIMATOR_H_
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