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
34 namespace blink {
35
36 namespace AudioUtilities {
37
decibelsToLinear(float decibels)38 float decibelsToLinear(float decibels)
39 {
40 return powf(10, 0.05f * decibels);
41 }
42
linearToDecibels(float linear)43 float 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
discreteTimeConstantForSampleRate(double timeConstant,double sampleRate)54 double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
55 {
56 return 1 - exp(-1 / (sampleRate * timeConstant));
57 }
58
timeToSampleFrame(double time,double sampleRate)59 size_t timeToSampleFrame(double time, double sampleRate)
60 {
61 return static_cast<size_t>(round(time * sampleRate));
62 }
63
isValidAudioBufferSampleRate(float sampleRate)64 bool isValidAudioBufferSampleRate(float sampleRate)
65 {
66 return sampleRate >= minAudioBufferSampleRate() && sampleRate <= maxAudioBufferSampleRate();
67 }
68
minAudioBufferSampleRate()69 float minAudioBufferSampleRate()
70 {
71 // crbug.com/344375
72 return 3000;
73 }
74
maxAudioBufferSampleRate()75 float 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