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 37 float decibelsToLinear(float decibels) 38 { 39 return powf(10, 0.05f * decibels); 40 } 41 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 53 double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate) 54 { 55 return 1 - exp(-1 / (sampleRate * timeConstant)); 56 } 57 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
