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/*
* Copyright (C) 2010 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "third_party/blink/renderer/platform/audio/distance_effect.h"
#include <math.h>
#include <algorithm>
#include "third_party/blink/renderer/platform/wtf/assertions.h"
#include "third_party/blink/renderer/platform/wtf/math_extras.h"
namespace blink {
DistanceEffect::DistanceEffect()
: model_(kModelInverse),
ref_distance_(1.0),
max_distance_(10000.0),
rolloff_factor_(1.0) {}
double DistanceEffect::Gain(double distance) {
switch (model_) {
case kModelLinear:
return LinearGain(distance);
case kModelInverse:
return InverseGain(distance);
case kModelExponential:
return ExponentialGain(distance);
}
NOTREACHED();
return 0.0;
}
double DistanceEffect::LinearGain(double distance) {
// Clamp refDistance and distance according to the spec.
double dref = std::min(ref_distance_, max_distance_);
double dmax = std::max(ref_distance_, max_distance_);
distance = clampTo(distance, dref, dmax);
if (dref == dmax)
return 1 - rolloff_factor_;
// We want a gain that decreases linearly from m_refDistance to
// m_maxDistance. The gain is 1 at m_refDistance.
return (1.0 - clampTo(rolloff_factor_, 0.0, 1.0) * (distance - dref) /
(dmax - dref));
}
double DistanceEffect::InverseGain(double distance) {
if (ref_distance_ == 0)
return 0;
// Clamp distance according to spec
distance = clampTo(distance, ref_distance_);
return ref_distance_ / (ref_distance_ + clampTo(rolloff_factor_, 0.0) *
(distance - ref_distance_));
}
double DistanceEffect::ExponentialGain(double distance) {
if (ref_distance_ == 0)
return 0;
// Clamp distance according to spec
distance = clampTo(distance, ref_distance_);
return pow(distance / ref_distance_, -clampTo(rolloff_factor_, 0.0));
}
} // namespace blink