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 "config.h"
30
31 #if ENABLE(WEB_AUDIO)
32
33 #include "platform/audio/Distance.h"
34 #include "wtf/Assertions.h"
35
36 #include <math.h>
37 #include <algorithm>
38
39 using namespace std;
40
41 namespace WebCore {
42
DistanceEffect()43 DistanceEffect::DistanceEffect()
44 : m_model(ModelInverse)
45 , m_isClamped(true)
46 , m_refDistance(1.0)
47 , m_maxDistance(10000.0)
48 , m_rolloffFactor(1.0)
49 {
50 }
51
gain(double distance)52 double DistanceEffect::gain(double distance)
53 {
54 // don't go beyond maximum distance
55 distance = min(distance, m_maxDistance);
56
57 // if clamped, don't get closer than reference distance
58 if (m_isClamped)
59 distance = max(distance, m_refDistance);
60
61 switch (m_model) {
62 case ModelLinear:
63 return linearGain(distance);
64 case ModelInverse:
65 return inverseGain(distance);
66 case ModelExponential:
67 return exponentialGain(distance);
68 }
69 ASSERT_NOT_REACHED();
70 return 0.0;
71 }
72
linearGain(double distance)73 double DistanceEffect::linearGain(double distance)
74 {
75 // We want a gain that decreases linearly from m_refDistance to
76 // m_maxDistance. The gain is 1 at m_refDistance.
77 return (1.0 - m_rolloffFactor * (distance - m_refDistance) / (m_maxDistance - m_refDistance));
78 }
79
inverseGain(double distance)80 double DistanceEffect::inverseGain(double distance)
81 {
82 return m_refDistance / (m_refDistance + m_rolloffFactor * (distance - m_refDistance));
83 }
84
exponentialGain(double distance)85 double DistanceEffect::exponentialGain(double distance)
86 {
87 return pow(distance / m_refDistance, -m_rolloffFactor);
88 }
89
90 } // namespace WebCore
91
92 #endif // ENABLE(WEB_AUDIO)
93