1 /*
2 * Copyright (C) 2010 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14 * its contributors may be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include "third_party/blink/renderer/platform/audio/distance_effect.h"
30
31 #include <math.h>
32 #include <algorithm>
33 #include "third_party/blink/renderer/platform/wtf/assertions.h"
34 #include "third_party/blink/renderer/platform/wtf/math_extras.h"
35
36 namespace blink {
37
DistanceEffect()38 DistanceEffect::DistanceEffect()
39 : model_(kModelInverse),
40 ref_distance_(1.0),
41 max_distance_(10000.0),
42 rolloff_factor_(1.0) {}
43
Gain(double distance)44 double DistanceEffect::Gain(double distance) {
45 switch (model_) {
46 case kModelLinear:
47 return LinearGain(distance);
48 case kModelInverse:
49 return InverseGain(distance);
50 case kModelExponential:
51 return ExponentialGain(distance);
52 }
53 NOTREACHED();
54 return 0.0;
55 }
56
LinearGain(double distance)57 double DistanceEffect::LinearGain(double distance) {
58 // Clamp refDistance and distance according to the spec.
59 double dref = std::min(ref_distance_, max_distance_);
60 double dmax = std::max(ref_distance_, max_distance_);
61 distance = clampTo(distance, dref, dmax);
62
63 if (dref == dmax)
64 return 1 - rolloff_factor_;
65
66 // We want a gain that decreases linearly from m_refDistance to
67 // m_maxDistance. The gain is 1 at m_refDistance.
68 return (1.0 - clampTo(rolloff_factor_, 0.0, 1.0) * (distance - dref) /
69 (dmax - dref));
70 }
71
InverseGain(double distance)72 double DistanceEffect::InverseGain(double distance) {
73 if (ref_distance_ == 0)
74 return 0;
75
76 // Clamp distance according to spec
77 distance = clampTo(distance, ref_distance_);
78
79 return ref_distance_ / (ref_distance_ + clampTo(rolloff_factor_, 0.0) *
80 (distance - ref_distance_));
81 }
82
ExponentialGain(double distance)83 double DistanceEffect::ExponentialGain(double distance) {
84 if (ref_distance_ == 0)
85 return 0;
86
87 // Clamp distance according to spec
88 distance = clampTo(distance, ref_distance_);
89
90 return pow(distance / ref_distance_, -clampTo(rolloff_factor_, 0.0));
91 }
92
93 } // namespace blink
94