1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/webaudio/blink/ZeroPole.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,78 @@
1.4 +/*
1.5 + * Copyright (C) 2011 Google Inc. All rights reserved.
1.6 + *
1.7 + * Redistribution and use in source and binary forms, with or without
1.8 + * modification, are permitted provided that the following conditions
1.9 + * are met:
1.10 + *
1.11 + * 1. Redistributions of source code must retain the above copyright
1.12 + * notice, this list of conditions and the following disclaimer.
1.13 + * 2. Redistributions in binary form must reproduce the above copyright
1.14 + * notice, this list of conditions and the following disclaimer in the
1.15 + * documentation and/or other materials provided with the distribution.
1.16 + * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
1.17 + * its contributors may be used to endorse or promote products derived
1.18 + * from this software without specific prior written permission.
1.19 + *
1.20 + * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
1.21 + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
1.22 + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
1.23 + * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
1.24 + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
1.25 + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
1.26 + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
1.27 + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
1.28 + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
1.29 + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.30 + */
1.31 +
1.32 +#include "ZeroPole.h"
1.33 +
1.34 +#include <cmath>
1.35 +#include <float.h>
1.36 +
1.37 +namespace WebCore {
1.38 +
1.39 +void ZeroPole::process(const float *source, float *destination, int framesToProcess)
1.40 +{
1.41 + float zero = m_zero;
1.42 + float pole = m_pole;
1.43 +
1.44 + // Gain compensation to make 0dB @ 0Hz
1.45 + const float k1 = 1 / (1 - zero);
1.46 + const float k2 = 1 - pole;
1.47 +
1.48 + // Member variables to locals.
1.49 + float lastX = m_lastX;
1.50 + float lastY = m_lastY;
1.51 +
1.52 + for (int i = 0; i < framesToProcess; ++i) {
1.53 + float input = source[i];
1.54 +
1.55 + // Zero
1.56 + float output1 = k1 * (input - zero * lastX);
1.57 + lastX = input;
1.58 +
1.59 + // Pole
1.60 + float output2 = k2 * output1 + pole * lastY;
1.61 + lastY = output2;
1.62 +
1.63 + destination[i] = output2;
1.64 + }
1.65 +
1.66 + // Locals to member variables. Flush denormals here so we don't
1.67 + // slow down the inner loop above.
1.68 + if (lastX == 0.0f && lastY != 0.0f && fabsf(lastY) < FLT_MIN) {
1.69 + // Flush future values to zero (until there is new input).
1.70 + lastY = 0.0;
1.71 + // Flush calculated values.
1.72 + for (int i = framesToProcess; i-- && fabsf(destination[i]) < FLT_MIN; ) {
1.73 + destination[i] = 0.0f;
1.74 + }
1.75 + }
1.76 +
1.77 + m_lastX = lastX;
1.78 + m_lastY = lastY;
1.79 +}
1.80 +
1.81 +} // namespace WebCore
