/*
* 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];
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);
}
}
/*! \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);
}
}
/*! \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);
}
}
/*! \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);
}
}
/*! \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));
}
}
/*! \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 iMiddleWindow = (sizeWindow+1) >> 1;
int iOffset = sizeFft - (iMiddleWindow - 1);
int i;
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];
}