ZeroPole.cpp (2793B)
1 /* 2 * Copyright (C) 2011 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 * 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of 14 * its contributors may be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include "ZeroPole.h" 30 31 #include <float.h> 32 33 #include <cmath> 34 35 #include "DenormalDisabler.h" 36 37 namespace WebCore { 38 39 void ZeroPole::process(const float* source, float* destination, 40 int framesToProcess) { 41 float zero = m_zero; 42 float pole = m_pole; 43 44 // Gain compensation to make 0dB @ 0Hz 45 const float k1 = 1 / (1 - zero); 46 const float k2 = 1 - pole; 47 48 // Member variables to locals. 49 float lastX = m_lastX; 50 float lastY = m_lastY; 51 52 for (int i = 0; i < framesToProcess; ++i) { 53 float input = source[i]; 54 55 // Zero 56 float output1 = k1 * (input - zero * lastX); 57 lastX = input; 58 59 // Pole 60 float output2 = k2 * output1 + pole * lastY; 61 lastY = output2; 62 63 destination[i] = output2; 64 } 65 66 // Locals to member variables. Flush denormals here so we don't 67 // slow down the inner loop above. 68 #ifndef HAVE_DENORMAL 69 if (lastX == 0.0f && lastY != 0.0f && fabsf(lastY) < FLT_MIN) { 70 // Flush future values to zero (until there is new input). 71 lastY = 0.0; 72 73 // Flush calculated values. 74 for (int i = framesToProcess; i-- && fabsf(destination[i]) < FLT_MIN;) { 75 destination[i] = 0.0f; 76 } 77 } 78 #endif 79 80 m_lastX = lastX; 81 m_lastY = lastY; 82 } 83 84 } // namespace WebCore