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 "platform/audio/AudioUtilities.h"
30
31#include "wtf/Assertions.h"
32#include "wtf/MathExtras.h"
33
34namespace blink {
35
36namespace AudioUtilities {
37
38float decibelsToLinear(float decibels)
39{
40    return powf(10, 0.05f * decibels);
41}
42
43float linearToDecibels(float linear)
44{
45    // It's not possible to calculate decibels for a zero linear value since it would be -Inf.
46    // -1000.0 dB represents a very tiny linear value in case we ever reach this case.
47    ASSERT(linear);
48    if (!linear)
49        return -1000;
50
51    return 20 * log10f(linear);
52}
53
54double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
55{
56    return 1 - exp(-1 / (sampleRate * timeConstant));
57}
58
59size_t timeToSampleFrame(double time, double sampleRate)
60{
61    return static_cast<size_t>(round(time * sampleRate));
62}
63
64bool isValidAudioBufferSampleRate(float sampleRate)
65{
66    return sampleRate >= minAudioBufferSampleRate() && sampleRate <= maxAudioBufferSampleRate();
67}
68
69float minAudioBufferSampleRate()
70{
71    // crbug.com/344375
72    return 3000;
73}
74
75float maxAudioBufferSampleRate()
76{
77    // Windows can support audio sampling rates this high, so allow AudioBuffer rates this high as well.
78    return 192000;
79}
80} // AudioUtilites
81
82} // namespace blink
83
84#endif // ENABLE(WEB_AUDIO)
85