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+/*
+ * Copyright (c) 2008 MUSIC TECHNOLOGY GROUP (MTG)
+ * UNIVERSITAT POMPEU FABRA
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+/*! \file windows.c
+ * \brief functions for creating various windows
+ *
+ * Use sms_getWindow() for selecting which window will be made
+ */
+#include "sms.h"
+
+
+/* \brief scale a window by its integral (numeric quadrature)
+ *
+ * In order to get a normalized magnitude spectrum (ex. Fourier analysis
+ * of a sinusoid with linear magnitude 1 gives one peak of magnitude 1 in
+ * the frequency domain), the spectrum windowing function should be
+ * normalized by its area under the curve.
+ *
+ * \param sizeWindow the size of the window
+ * \param pWindow pointer to an array that will hold the window
+ */
+void sms_scaleWindow ( int sizeWindow, sfloat *pWindow)
+{
+
+ int i;
+ sfloat fSum = 0;
+ sfloat fScale;
+
+ for(i = 0; i < sizeWindow; i++)
+ fSum += pWindow[i];
+
+/* fSum = fSum / 2; */
+/* for(i = 0; i < sizeWindow; i++) */
+/* pWindow[i] /= fSum; */
+
+ fScale = 2. / fSum;
+
+ for(i = 0; i < sizeWindow; i++)
+ pWindow[i] *= fScale;
+}
+
+/*! \brief window to be used in the IFFT synthesis
+ *
+ * contains both an inverse Blackman-Harris and triangular window.
+ *
+ * \todo read X. Rodet, Ph. Depalle, "Spectral Envelopes and Inverse FFT
+ * Synthesis." Proc. 93rd AES Convention, October 1992
+ * \param sizeWindow the size of the window
+ * \param pFWindow pointer to an array that will hold the window
+ */
+void IFFTwindow (int sizeWindow, sfloat *pFWindow)
+{
+
+ int i;
+ sfloat a0 = .35875, a1 = .48829, a2 = .14128, a3 = .01168;
+ double fConst = TWO_PI / sizeWindow, fIncr = 2.0 /sizeWindow, fVal = 0;
+
+ /* compute inverse of Blackman-Harris 92dB window */
+ for(i = 0; i < sizeWindow; i++)
+ {
+ pFWindow[i] = 1 / (a0 - a1 * cos(fConst * i) +
+ a2 * cos(fConst * 2 * i) - a3 * cos(fConst * 3 * i));
+ }
+
+ /* scale function by a triangular */
+ for (i = 0; i < sizeWindow / 2; i++)
+ {
+ pFWindow[i] = fVal * pFWindow[i] / 2.787457;
+ fVal += fIncr;
+ }
+ for (i = sizeWindow / 2; i < sizeWindow; i++)
+ {
+ pFWindow[i] = fVal * pFWindow[i] / 2.787457;
+ fVal -= fIncr;
+ }
+}
+
+/*! \brief BlackmanHarris window with 62dB rolloff
+ *
+ * \todo where did these come from?
+ * \param sizeWindow the size of the window
+ * \param pFWindow pointer to an array that will hold the window
+ */
+void BlackmanHarris62 (int sizeWindow, sfloat *pFWindow)
+{
+ int i;
+ double fSum = 0;
+ /* for 3 term -62.05 */
+ sfloat a0 = .44959, a1 = .49364, a2 = .05677;
+ double fConst = TWO_PI / sizeWindow;
+
+ /* compute window */
+ for(i = 0; i < sizeWindow; i++)
+ {
+ fSum += pFWindow[i] = a0 - a1 * cos(fConst * i) +
+ a2 * cos(fConst * 2 * i);
+ }
+
+ /* I do not know why I now need this factor of two */
+/* fSum = fSum / 2; */
+
+/* /\* scale function *\/ */
+/* for (i = 0; i < sizeWindow; i++) */
+/* pFWindow[i] = pFWindow[i] / fSum; */
+}
+
+/*! \brief BlackmanHarris window with 70dB rolloff
+ *
+ * \param sizeWindow the size of the window
+ * \param pFWindow pointer to an array that will hold the window
+ */
+void BlackmanHarris70 (int sizeWindow, sfloat *pFWindow)
+{
+ int i;
+ double fSum = 0;
+ /* for 3 term -70.83 */
+ sfloat a0 = .42323, a1 = .49755, a2 = .07922;
+ double fConst = TWO_PI / sizeWindow;
+
+ /* compute window */
+ for(i = 0; i < sizeWindow; i++)
+ {
+ fSum += pFWindow[i] = a0 - a1 * cos(fConst * i) +
+ a2 * cos(fConst * 2 * i);
+ }
+
+/* fSum = fSum / 2; */
+
+/* /\* scale function *\/ */
+/* for (i = 0; i < sizeWindow; i++) */
+/* { */
+/* pFWindow[i] = pFWindow[i] / fSum; */
+/* } */
+}
+
+/*! \brief BlackmanHarris window with 74dB rolloff
+ *
+ * \param sizeWindow the size of the window
+ * \param pFWindow pointer to an array that will hold the window
+ */
+void BlackmanHarris74 (int sizeWindow, sfloat *pFWindow)
+{
+ int i;
+ double fSum = 0;
+ /* for -74dB from the Nuttall paper */
+ sfloat a0 = .40217, a1 = .49703, a2 = .09892, a3 = .00188;
+ double fConst = TWO_PI / sizeWindow;
+
+ /* compute window */
+ for(i = 0; i < sizeWindow; i++)
+ {
+ fSum += pFWindow[i] = a0 - a1 * cos(fConst * i) +
+ a2 * cos(fConst * 2 * i) + a3 * cos(fConst * 3 * i);
+ }
+
+ /* I do not know why I now need this factor of two */
+/* fSum = fSum / 2; */
+
+/* /\* scale function *\/ */
+/* for (i = 0; i < sizeWindow; i++) */
+/* pFWindow[i] = pFWindow[i] / fSum; */
+}
+
+/*! \brief BlackmanHarris window with 92dB rolloff
+ *
+ * \param sizeWindow the size of the window
+ * \param pFWindow pointer to an array that will hold the window
+ */
+void BlackmanHarris92 (int sizeWindow, sfloat *pFWindow)
+{
+ int i;
+ double fSum = 0;
+ /* for -92dB */
+ sfloat a0 = .35875, a1 = .48829, a2 = .14128, a3 = .01168;
+ double fConst = TWO_PI / sizeWindow;
+
+ /* compute window */
+ for(i = 0; i < sizeWindow; i++)
+ {
+ fSum += pFWindow[i] = a0 - a1 * cos(fConst * i) +
+ a2 * cos(fConst * 2 * i) + a3 * cos(fConst * 3 * i);
+ }
+
+ /* I do not know why I now need this factor of two */
+/* fSum = fSum / 2; */
+/* /\* scale function *\/ */
+/* for (i = 0; i < sizeWindow; i++) */
+/* pFWindow[i] = pFWindow[i] / fSum; */
+}
+
+/*! \brief default BlackmanHarris window (70dB rolloff)
+ *
+ * \param sizeWindow the size of the window
+ * \param pFWindow pointer to an array that will hold the window
+ */
+void BlackmanHarris (int sizeWindow, sfloat *pFWindow)
+{
+ BlackmanHarris70 (sizeWindow, pFWindow);
+}
+
+/*! \brief Hamming window
+ *
+ *
+ *
+ * \param sizeWindow window size
+ * \param pWindow window array
+ */
+void Hamming (int sizeWindow, sfloat *pWindow)
+{
+ int i;
+ sfloat fSum = 0;
+
+ for(i = 0; i < sizeWindow; i++)
+ {
+ fSum += pWindow[i] = 0.53836 - 0.46164*cos(TWO_PI*i/(sizeWindow-1));
+ }
+
+ //ScaleWindow(sizeWindow, pWindow);
+/* fSum = fSum / 2; */
+/* for(i = 0; i < sizeWindow; i++) */
+/* pFWindow[i] /= fSum; */
+}
+
+/*! \brief Hanning window
+ *
+ * \param sizeWindow window size
+ * \param pWindow window array
+ */
+void Hanning (int sizeWindow, sfloat *pWindow)
+{
+ int i;
+ for(i = 0; i < sizeWindow; i++)
+ pWindow[i] = (sin(PI*i/(sizeWindow-1)))*(sin(PI*i/(sizeWindow-1)));
+}
+
+/*! \brief main function for getting various windows
+ *
+ * \todo note on window scales
+ *
+ * \see SMS_WINDOWS for the different window types available
+ * \param sizeWindow window size
+ * \param pFWindow window array
+ * \param iWindowType the desired window type defined by #SMS_WINDOWS
+ */
+void sms_getWindow (int sizeWindow, sfloat *pFWindow, int iWindowType)
+{
+ switch (iWindowType)
+ {
+ case SMS_WIN_BH_62:
+ BlackmanHarris62 (sizeWindow, pFWindow);
+ break;
+ case SMS_WIN_BH_70:
+ BlackmanHarris70 (sizeWindow, pFWindow);
+ break;
+ case SMS_WIN_BH_74:
+ BlackmanHarris74 (sizeWindow, pFWindow);
+ break;
+ case SMS_WIN_BH_92:
+ BlackmanHarris92 (sizeWindow, pFWindow);
+ break;
+ case SMS_WIN_HAMMING:
+ Hamming (sizeWindow, pFWindow);
+ break;
+ case SMS_WIN_HANNING:
+ Hanning (sizeWindow, pFWindow);
+ break;
+ case SMS_WIN_IFFT:
+ IFFTwindow (sizeWindow, pFWindow);
+ break;
+ default:
+ BlackmanHarris (sizeWindow, pFWindow);
+ }
+}
+
+/*! \brief apply a window and center around sample 0
+ *
+ * function to center a waveform around sample 0, also known
+ * as 'zero-phase windowing'. Half the samples are at the beginning,
+ * half at the end, with the remaining samples (sizeFft-sizeWindow)
+ * in the middle (zero-padding for an interpolated spectrum).
+ *
+ * \todo do I need to garuntee that sizeWindow is odd-lengthed?
+ *
+ * \param sizeWindow size of waveform/waveform
+ * \param pWaveform pointer to waveform
+ * \param pWindow pointer to window
+ * \param sizeFft size of FFT
+ * \param pFftBuffer pointer to FFT buffer
+ */
+void sms_windowCentered (int sizeWindow, sfloat *pWaveform, sfloat *pWindow, int sizeFft, sfloat *pFftBuffer)
+{
+ int i, iOffset, iMiddleWindow;
+
+ iMiddleWindow = (sizeWindow+1) >> 1;
+ iOffset = sizeFft - (iMiddleWindow - 1);
+ for (i=0; i<iMiddleWindow-1; i++)
+ pFftBuffer[iOffset + i] = pWindow[i] * pWaveform[i];
+ iOffset = iMiddleWindow - 1;
+ for (i=0; i<iMiddleWindow; i++)
+ pFftBuffer[i] = pWindow[iOffset + i] * pWaveform[iOffset + i];
+}
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