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