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
32namespace WebCore {
33
34namespace AudioUtilities {
35
36float decibelsToLinear(float decibels)
37{
38 return powf(10, 0.05f * decibels);
39}
40
41float linearToDecibels(float 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;
48
49 return 20 * log10f(linear);
50}
51
52double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
53{
54 return 1 - exp(-1 / (sampleRate * timeConstant));
55}
56
57size_t timeToSampleFrame(double time, double sampleRate)
58{
59 return static_cast<size_t>(round(time * sampleRate));
60}
61} // AudioUtilites
62
63} // WebCore
64
65#endif // ENABLE(WEB_AUDIO)
66