video_cadence_estimator.cc | Explore in Territory

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/filters/video_cadence_estimator.h"

#include <algorithm>
#include <cmath>
#include <iterator>
#include <limits>
#include <numeric>
#include <string>

#include "base/logging.h"
#include "base/metrics/histogram_macros.h"
#include "media/base/media_switches.h"

namespace media {

// To prevent oscillation in and out of cadence or between cadence values, we
// require some time to elapse before a cadence switch is accepted.
const int kMinimumCadenceDurationMs = …;

// The numbers are used to decide whether the current video is variable FPS or
// constant FPS. If ratio of the sample deviation and the render length is
// above |kVariableFPSFactor|, then it is recognized as a variable FPS, and if
// the ratio is below |kConstantFPSFactor|, then it is recognized as a constant
// FPS, and if the ratio is in between the two factors, then we do not change
// previous recognition.
const double kVariableFPSFactor = …;
const double kConstantFPSFactor = …;

// Records the number of cadence changes to UMA.
static void HistogramCadenceChangeCount(int cadence_changes) { … }

// Construct a Cadence vector, a vector of integers satisfying the following
// conditions:
// 1. Size is |n|.
// 2. Sum of entries is |k|.
// 3. Each entry is in {|k|/|n|, |k|/|n| + 1}.
// 4. Distribution of |k|/|n| and |k|/|n| + 1 is as even as possible.
VideoCadenceEstimator::Cadence ConstructCadence(int k, int n) { … }

VideoCadenceEstimator::Cadence ConstructSimpleCadence(
    double perfect_cadence,
    base::TimeDelta max_acceptable_drift,
    base::TimeDelta* time_until_max_drift) { … }

VideoCadenceEstimator::VideoCadenceEstimator(
    base::TimeDelta minimum_time_until_max_drift)
    : … { … }

VideoCadenceEstimator::~VideoCadenceEstimator() = default;

void VideoCadenceEstimator::Reset() { … }

bool VideoCadenceEstimator::UpdateCadenceEstimate(
    base::TimeDelta render_interval,
    base::TimeDelta frame_duration,
    base::TimeDelta frame_duration_deviation,
    base::TimeDelta max_acceptable_drift) { … }

void VideoCadenceEstimator::UpdateCadenceInternal(
    Cadence new_cadence,
    base::TimeDelta time_until_max_drift) { … }

int VideoCadenceEstimator::GetCadenceForFrame(uint64_t frame_number) const { … }

bool VideoCadenceEstimator::HasSimpleCadence(
    base::TimeDelta render_interval,
    base::TimeDelta frame_duration,
    base::TimeDelta minimum_time_until_max_drift) { … }

VideoCadenceEstimator::Cadence VideoCadenceEstimator::CalculateCadence(
    base::TimeDelta render_interval,
    base::TimeDelta frame_duration,
    base::TimeDelta max_acceptable_drift,
    base::TimeDelta* time_until_max_drift) const { … }

std::string VideoCadenceEstimator::CadenceToString(
    const Cadence& cadence) const { … }

double VideoCadenceEstimator::avg_cadence_for_testing() const { … }

}  // namespace media
chromium/media/filters/video_cadence_estimator.cc
