Source/WebCore/platform/audio/ZeroPole.cpp

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 *     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
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "ZeroPole.h"

#include "DenormalDisabler.h"

namespace WebCore {

void ZeroPole::process(const float *source, float *destination, unsigned 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;

    while (framesToProcess--) {
        float input = *source++;

        // Zero
        float output1 = k1 * (input - zero * lastX);
        lastX = input;

        // Pole
        float output2 = k2 * output1 + pole * lastY;
        lastY = output2;

        *destination++ = output2;
    }
    
    // Locals to member variables. Flush denormals here so we don't
    // slow down the inner loop above.
    m_lastX = DenormalDisabler::flushDenormalFloatToZero(lastX);
    m_lastY = DenormalDisabler::flushDenormalFloatToZero(lastY);
}

} // namespace WebCore

#endif // ENABLE(WEB_AUDIO)