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/*
* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_
#define MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_
#include "rtc_base/checks.h"
namespace webrtc {
class ThresholdCurve {
public:
struct Point {
constexpr Point(float x, float y) : x(x), y(y) {}
float x;
float y;
};
// ThresholdCurve defines a curve. The curve is characterized by the two
// conjunction points: A and B. The curve segments the metric space into
// three domains - above the curve, on it and below it.
//
// y-axis ^ |
// | A|
// | \ A: (a.x, a.y)
// | \ B: (b.x, b.y)
// | B\________
// |---------------> bandwidth
//
// If either a.x == b.x or a.y == b.y, the curve can be defined
// by a single point. (We merge the two points into one - either the lower or
// the leftmost one - for easier treatment.)
//
// y-axis ^ |
// | |
// | |
// | |
// | P|__________
// |---------------> bandwidth
ThresholdCurve(const Point& left, const Point& right)
: a(GetPoint(left, right, true)),
b(GetPoint(left, right, false)),
slope(b.x - a.x == 0.0f ? 0.0f : (b.y - a.y) / (b.x - a.x)),
offset(a.y - slope * a.x) {
// TODO(eladalon): We might want to introduce some numerical validations.
}
ThresholdCurve(float a_x, float a_y, float b_x, float b_y)
: ThresholdCurve(Point{a_x, a_y}, Point{b_x, b_y}) {}
// Checks if a point is strictly below the curve.
bool IsBelowCurve(const Point& p) const {
if (p.x < a.x) {
return true;
} else if (p.x == a.x) {
// In principle, we could merge this into the next else, but to avoid
// numerical errors, we treat it separately.
return p.y < a.y;
} else if (a.x < p.x && p.x < b.x) {
return p.y < offset + slope * p.x;
} else { // if (b.x <= p.x)
return p.y < b.y;
}
}
// Checks if a point is strictly above the curve.
bool IsAboveCurve(const Point& p) const {
if (p.x <= a.x) {
return false;
} else if (a.x < p.x && p.x < b.x) {
return p.y > offset + slope * p.x;
} else { // if (b.x <= p.x)
return p.y > b.y;
}
}
bool operator<=(const ThresholdCurve& rhs) const {
// This curve is <= the rhs curve if no point from this curve is
// above a corresponding point from the rhs curve.
return !IsBelowCurve(rhs.a) && !IsBelowCurve(rhs.b) &&
!rhs.IsAboveCurve(a) && !rhs.IsAboveCurve(b);
}
private:
static const Point& GetPoint(const Point& left,
const Point& right,
bool is_for_left) {
RTC_DCHECK_LE(left.x, right.x);
RTC_DCHECK_GE(left.y, right.y);
// Same X-value or Y-value triggers merging both points to the
// lower and/or left of the two points, respectively.
if (left.x == right.x) {
return right;
} else if (left.y == right.y) {
return left;
}
// If unmerged, boolean flag determines which of the points is desired.
return is_for_left ? left : right;
}
const Point a;
const Point b;
const float slope;
const float offset;
};
} // namespace webrtc
#endif // MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_