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 #include "wtf/Assertions.h"
31 #include "wtf/MathExtras.h"
32
33 namespace WebCore {
34
35 namespace AudioUtilities {
36
decibelsToLinear(float decibels)37 float decibelsToLinear(float decibels)
38 {
39 return powf(10, 0.05f * decibels);
40 }
41
linearToDecibels(float linear)42 float linearToDecibels(float linear)
43 {
44 // It's not possible to calculate decibels for a zero linear value since it would be -Inf.
45 // -1000.0 dB represents a very tiny linear value in case we ever reach this case.
46 ASSERT(linear);
47 if (!linear)
48 return -1000;
49
50 return 20 * log10f(linear);
51 }
52
discreteTimeConstantForSampleRate(double timeConstant,double sampleRate)53 double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
54 {
55 return 1 - exp(-1 / (sampleRate * timeConstant));
56 }
57
timeToSampleFrame(double time,double sampleRate)58 size_t timeToSampleFrame(double time, double sampleRate)
59 {
60 return static_cast<size_t>(round(time * sampleRate));
61 }
62 } // AudioUtilites
63
64 } // WebCore
65
66 #endif // ENABLE(WEB_AUDIO)
67