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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 spectralApprox.c
* \brief line segment approximation of a magnitude spectrum
*/
#include "sms.h"
/*! \brief approximate a magnitude spectrum
* First downsampling using local maxima and then upsampling using linear
* interpolation. The output spectrum doesn't have to be the same size as
* the input one.
*
* \param pFSpec1 magnitude spectrum to approximate
* \param sizeSpec1 size of input spectrum
* \param sizeSpec1Used size of the spectrum to use
* \param pFSpec2 output envelope
* \param sizeSpec2 size of output envelope
* \param nCoefficients number of coefficients to use in approximation
* \return error code \see SMS_ERRORS
*/
int sms_spectralApprox(sfloat *pFSpec1, int sizeSpec1, int sizeSpec1Used,
sfloat *pFSpec2, int sizeSpec2, int nCoefficients,
sfloat *envelope)
{
sfloat fHopSize, fCurrentLoc = 0, fLeft = 0, fRight = 0, fValue = 0,
fLastLocation, fSizeX, fSpec2Acum=0, fNextHop, fDeltaY;
int iFirstGood = 0, iLastSample = 0, i, j;
/* when number of coefficients is smaller than 2 do not approximate */
if(nCoefficients < 2)
{
for(i = 0; i < sizeSpec2; i++)
pFSpec2[i] = 1;
return SMS_OK;
}
/* calculate the hop size */
if(nCoefficients > sizeSpec1)
nCoefficients = sizeSpec1;
fHopSize = (sfloat)sizeSpec1Used / nCoefficients;
/* approximate by linear interpolation */
if(fHopSize > 1)
{
iFirstGood = 0;
for(i = 0; i < nCoefficients; i++)
{
iLastSample = fLastLocation = fCurrentLoc + fHopSize;
iLastSample = MIN(sizeSpec1-1, iLastSample);
if(iLastSample < sizeSpec1-1)
{
fRight = pFSpec1[iLastSample] +
(pFSpec1[iLastSample+1] - pFSpec1[iLastSample]) *
(fLastLocation - iLastSample);
}
else
{
fRight = pFSpec1[iLastSample];
}
fValue = 0;
for(j = iFirstGood; j <= iLastSample; j++)
fValue = MAX (fValue, pFSpec1[j]);
fValue = MAX(fValue, MAX (fRight, fLeft));
envelope[i] = fValue;
fLeft = fRight;
fCurrentLoc = fLastLocation;
iFirstGood = (int)(1+ fCurrentLoc);
}
}
else if(fHopSize == 1)
{
for(i = 0; i < nCoefficients; i++)
envelope[i] = pFSpec1[i];
}
else
{
sms_error("SpectralApprox: sizeSpec1 has too many nCoefficients"); /* \todo need to increase the frequency? */
return -1;
}
/* Creates Spec2 from Envelope */
if(nCoefficients < sizeSpec2)
{
fSizeX = (sfloat) (sizeSpec2-1) / nCoefficients;
/* the first step */
fNextHop = fSizeX / 2;
fDeltaY = envelope[0] / fNextHop;
fSpec2Acum=pFSpec2[j=0]=0;
while(++j < fNextHop)
pFSpec2[j] = (fSpec2Acum += fDeltaY);
/* middle values */
for(i = 0; i <= nCoefficients-2; ++i)
{
fDeltaY = (envelope[i+1] - envelope[i]) / fSizeX;
/* first point of a segment */
pFSpec2[j] = (fSpec2Acum = (envelope[i]+(fDeltaY*(j-fNextHop))));
++j;
/* remaining points */
fNextHop += fSizeX;
while(j < fNextHop)
pFSpec2[j++] = (fSpec2Acum += fDeltaY);
}
/* last step */
fDeltaY = -envelope[i] * 2 / fSizeX;
/* first point of the last segment */
pFSpec2[j] = (fSpec2Acum = (envelope[i]+(fDeltaY*(j-fNextHop))));
++j;
fNextHop += fSizeX / 2;
while(j < sizeSpec2-1)
pFSpec2[j++]=(fSpec2Acum += fDeltaY);
/* last should be exactly zero */
pFSpec2[sizeSpec2-1] = .0;
}
else if(nCoefficients == sizeSpec2)
{
for(i = 0; i < nCoefficients; i++)
pFSpec2[i] = envelope[i];
}
else
{
sms_error("SpectralApprox: sizeSpec2 has too many nCoefficients\n");
return -1;
}
return SMS_OK;
}
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