michael@0: /*
michael@0:  * Copyright (C) 2011 Google Inc. All rights reserved.
michael@0:  *
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  *
michael@0:  * 1.  Redistributions of source code must retain the above copyright
michael@0:  *     notice, this list of conditions and the following disclaimer.
michael@0:  * 2.  Redistributions in binary form must reproduce the above copyright
michael@0:  *     notice, this list of conditions and the following disclaimer in the
michael@0:  *     documentation and/or other materials provided with the distribution.
michael@0:  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
michael@0:  *     its contributors may be used to endorse or promote products derived
michael@0:  *     from this software without specific prior written permission.
michael@0:  *
michael@0:  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
michael@0:  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
michael@0:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
michael@0:  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
michael@0:  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
michael@0:  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
michael@0:  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0:  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
michael@0:  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  */
michael@0: 
michael@0: #include "ZeroPole.h"
michael@0: 
michael@0: #include <cmath>
michael@0: #include <float.h>
michael@0: 
michael@0: namespace WebCore {
michael@0: 
michael@0: void ZeroPole::process(const float *source, float *destination, int framesToProcess)
michael@0: {
michael@0:     float zero = m_zero;
michael@0:     float pole = m_pole;
michael@0: 
michael@0:     // Gain compensation to make 0dB @ 0Hz
michael@0:     const float k1 = 1 / (1 - zero);
michael@0:     const float k2 = 1 - pole;
michael@0:     
michael@0:     // Member variables to locals.
michael@0:     float lastX = m_lastX;
michael@0:     float lastY = m_lastY;
michael@0: 
michael@0:     for (int i = 0; i < framesToProcess; ++i) {
michael@0:         float input = source[i];
michael@0: 
michael@0:         // Zero
michael@0:         float output1 = k1 * (input - zero * lastX);
michael@0:         lastX = input;
michael@0: 
michael@0:         // Pole
michael@0:         float output2 = k2 * output1 + pole * lastY;
michael@0:         lastY = output2;
michael@0: 
michael@0:         destination[i] = output2;
michael@0:     }
michael@0:     
michael@0:     // Locals to member variables. Flush denormals here so we don't
michael@0:     // slow down the inner loop above.
michael@0:     if (lastX == 0.0f && lastY != 0.0f && fabsf(lastY) < FLT_MIN) {
michael@0:         // Flush future values to zero (until there is new input).
michael@0:         lastY = 0.0;
michael@0:         // Flush calculated values.
michael@0:         for (int i = framesToProcess; i-- && fabsf(destination[i]) < FLT_MIN; ) {
michael@0:             destination[i] = 0.0f;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     m_lastX = lastX;
michael@0:     m_lastY = lastY;
michael@0: }
michael@0: 
michael@0: } // namespace WebCore