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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 WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_ #define WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_ #include "webrtc/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 // WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_UTIL_THRESHOLD_CURVE_H_