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 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
16 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
17 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
18 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
19 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
20 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
22 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25 #include "config.h"
26
27 #if ENABLE(WEB_AUDIO)
28
29 #include "AudioUtilities.h"
30 #include <wtf/MathExtras.h>
31
32 namespace WebCore {
33
34 namespace AudioUtilities {
35
decibelsToLinear(double decibels)36 double decibelsToLinear(double decibels)
37 {
38 return pow(10.0, 0.05 * decibels);
39 }
40
linearToDecibels(double linear)41 double linearToDecibels(double linear)
42 {
43 // It's not possible to calculate decibels for a zero linear value since it would be -Inf.
44 // -1000.0 dB represents a very tiny linear value in case we ever reach this case.
45 ASSERT(linear);
46 if (!linear)
47 return -1000.0;
48
49 return 20.0 * log10(linear);
50 }
51
discreteTimeConstantForSampleRate(double timeConstant,double sampleRate)52 double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
53 {
54 // hardcoded value is temporary build fix for Windows.
55 // FIXME: replace hardcode 2.718282 with M_E until the correct MathExtras.h solution is determined.
56 return 1.0 - pow(1.0 / 2.718282, 1.0 / (sampleRate * timeConstant));
57 }
58
59 } // AudioUtilites
60
61 } // WebCore
62
63 #endif // ENABLE(WEB_AUDIO)
64