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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