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 "EqualPowerPanner.h" 30 31 #include "AudioBus.h" 32 #include "AudioUtilities.h" 33 #include <wtf/MathExtras.h> 34 35 // Use a 50ms smoothing / de-zippering time-constant. 36 const double SmoothingTimeConstant = 0.050; 37 38 namespace WebCore { 39 40 EqualPowerPanner::EqualPowerPanner(double sampleRate) 41 : Panner(PanningModelEqualPower) 42 , m_isFirstRender(true) 43 , m_gainL(0.0) 44 , m_gainR(0.0) 45 { 46 m_smoothingConstant = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate); 47 } 48 49 void EqualPowerPanner::pan(double azimuth, double /*elevation*/, AudioBus* inputBus, AudioBus* outputBus, size_t framesToProcess) 50 { 51 // FIXME: implement stereo sources 52 bool isInputSafe = inputBus && inputBus->numberOfChannels() == 1 && framesToProcess <= inputBus->length(); 53 ASSERT(isInputSafe); 54 if (!isInputSafe) 55 return; 56 57 bool isOutputSafe = outputBus && outputBus->numberOfChannels() == 2 && framesToProcess <= outputBus->length(); 58 ASSERT(isOutputSafe); 59 if (!isOutputSafe) 60 return; 61 62 AudioChannel* channel = inputBus->channel(0); 63 float* sourceP = channel->data(); 64 float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->data(); 65 float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->data(); 66 67 if (!sourceP || !destinationL || !destinationR) 68 return; 69 70 // Pan smoothly from left to right with azimuth going from -30 -> +30 degrees. 71 double desiredPanPosition; 72 if (azimuth > 30.0) 73 desiredPanPosition = 1.0; 74 else if (azimuth < -30.0) 75 desiredPanPosition = 0.0; 76 else 77 desiredPanPosition = (azimuth + 30.0) / 60.0; 78 79 double desiredGainL = 0.5 * cos(piDouble * desiredPanPosition) + 0.5; 80 double desiredGainR = sqrt(1.0 - desiredGainL*desiredGainL); 81 82 // Don't de-zipper on first render call. 83 if (m_isFirstRender) { 84 m_isFirstRender = false; 85 m_gainL = desiredGainL; 86 m_gainR = desiredGainR; 87 } 88 89 // Cache in local variables. 90 double gainL = m_gainL; 91 double gainR = m_gainR; 92 93 // Get local copy of smoothing constant. 94 const double SmoothingConstant = m_smoothingConstant; 95 96 int n = framesToProcess; 97 98 while (n--) { 99 float input = *sourceP++; 100 gainL += (desiredGainL - gainL) * SmoothingConstant; 101 gainR += (desiredGainR - gainR) * SmoothingConstant; 102 *destinationL++ = static_cast<float>(input * gainL); 103 *destinationR++ = static_cast<float>(input * gainR); 104 } 105 106 m_gainL = gainL; 107 m_gainR = gainR; 108 } 109 110 } // namespace WebCore 111 112 #endif // ENABLE(WEB_AUDIO) 113
