1 /* 2 * Copyright (c) 2017 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_ 12 #define MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_ 13 14 #include "rtc_base/checks.h" 15 16 namespace webrtc { 17 18 class ThresholdCurve { 19 public: 20 struct Point { PointPoint21 constexpr Point(float x, float y) : x(x), y(y) {} 22 float x; 23 float y; 24 }; 25 26 // ThresholdCurve defines a curve. The curve is characterized by the two 27 // conjunction points: A and B. The curve segments the metric space into 28 // three domains - above the curve, on it and below it. 29 // 30 // y-axis ^ | 31 // | A| 32 // | \ A: (a.x, a.y) 33 // | \ B: (b.x, b.y) 34 // | B\________ 35 // |---------------> bandwidth 36 // 37 // If either a.x == b.x or a.y == b.y, the curve can be defined 38 // by a single point. (We merge the two points into one - either the lower or 39 // the leftmost one - for easier treatment.) 40 // 41 // y-axis ^ | 42 // | | 43 // | | 44 // | | 45 // | P|__________ 46 // |---------------> bandwidth ThresholdCurve(const Point & left,const Point & right)47 ThresholdCurve(const Point& left, const Point& right) 48 : a(GetPoint(left, right, true)), 49 b(GetPoint(left, right, false)), 50 slope(b.x - a.x == 0.0f ? 0.0f : (b.y - a.y) / (b.x - a.x)), 51 offset(a.y - slope * a.x) { 52 // TODO(eladalon): We might want to introduce some numerical validations. 53 } 54 ThresholdCurve(float a_x,float a_y,float b_x,float b_y)55 ThresholdCurve(float a_x, float a_y, float b_x, float b_y) 56 : ThresholdCurve(Point{a_x, a_y}, Point{b_x, b_y}) {} 57 58 // Checks if a point is strictly below the curve. IsBelowCurve(const Point & p)59 bool IsBelowCurve(const Point& p) const { 60 if (p.x < a.x) { 61 return true; 62 } else if (p.x == a.x) { 63 // In principle, we could merge this into the next else, but to avoid 64 // numerical errors, we treat it separately. 65 return p.y < a.y; 66 } else if (a.x < p.x && p.x < b.x) { 67 return p.y < offset + slope * p.x; 68 } else { // if (b.x <= p.x) 69 return p.y < b.y; 70 } 71 } 72 73 // Checks if a point is strictly above the curve. IsAboveCurve(const Point & p)74 bool IsAboveCurve(const Point& p) const { 75 if (p.x <= a.x) { 76 return false; 77 } else if (a.x < p.x && p.x < b.x) { 78 return p.y > offset + slope * p.x; 79 } else { // if (b.x <= p.x) 80 return p.y > b.y; 81 } 82 } 83 84 bool operator<=(const ThresholdCurve& rhs) const { 85 // This curve is <= the rhs curve if no point from this curve is 86 // above a corresponding point from the rhs curve. 87 return !IsBelowCurve(rhs.a) && !IsBelowCurve(rhs.b) && 88 !rhs.IsAboveCurve(a) && !rhs.IsAboveCurve(b); 89 } 90 91 private: GetPoint(const Point & left,const Point & right,bool is_for_left)92 static const Point& GetPoint(const Point& left, 93 const Point& right, 94 bool is_for_left) { 95 RTC_DCHECK_LE(left.x, right.x); 96 RTC_DCHECK_GE(left.y, right.y); 97 98 // Same X-value or Y-value triggers merging both points to the 99 // lower and/or left of the two points, respectively. 100 if (left.x == right.x) { 101 return right; 102 } else if (left.y == right.y) { 103 return left; 104 } 105 106 // If unmerged, boolean flag determines which of the points is desired. 107 return is_for_left ? left : right; 108 } 109 110 const Point a; 111 const Point b; 112 const float slope; 113 const float offset; 114 }; 115 116 } // namespace webrtc 117 118 #endif // MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_ 119