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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 filters.c
* \brief various filters
*/
#include "sms.h"
/*! \brief coefficient for pre_emphasis filter */
#define SMS_EMPH_COEF .9
/* pre-emphasis filter function, it returns the filtered value
*
* sfloat fInput; sound sample
*/
sfloat sms_preEmphasis(sfloat fInput, SMS_AnalParams *pAnalParams)
{
if(pAnalParams->preEmphasis)
{
sfloat fOutput = fInput - SMS_EMPH_COEF * pAnalParams->preEmphasisLastValue;
pAnalParams->preEmphasisLastValue = fOutput;
return fOutput;
}
return fInput;
}
/* de-emphasis filter function, it returns the filtered value
*
* sfloat fInput; sound input
*/
sfloat sms_deEmphasis(sfloat fInput, SMS_SynthParams *pSynthParams)
{
if(pSynthParams->deEmphasis)
{
sfloat fOutput = fInput + SMS_EMPH_COEF * pSynthParams->deEmphasisLastValue;
pSynthParams->deEmphasisLastValue = fInput;
return fOutput;
}
return fInput;
}
/*! \brief function to implement a zero-pole filter
*
* \todo will forgetting to reset pD to zero at the beginning of a new analysis
* (when there are multiple analyses within the life of one program)
* cause problems?
*
* \param pFa pointer to numerator coefficients
* \param pFb pointer to denominator coefficients
* \param nCoeff number of coefficients
* \param fInput input sample
* \return value is the filtered sample
*/
static sfloat ZeroPoleFilter(sfloat *pFa, sfloat *pFb, int nCoeff, sfloat fInput )
{
double fOut = 0;
int iSection;
static sfloat pD[5] = {0, 0, 0, 0, 0};
pD[0] = fInput;
for (iSection = nCoeff-1; iSection > 0; iSection--)
{
fOut = fOut + pFa[iSection] * pD[iSection];
pD[0] = pD[0] - pFb[iSection] * pD[iSection];
pD[iSection] = pD [iSection-1];
}
fOut = fOut + pFa[0] * pD[0];
return (sfloat) fOut;
}
/*! \brief function to filter a waveform with a high-pass filter
*
* cutoff =1500 Hz
*
* \todo this filter only works on sample rates up to 48k?
*
* \param sizeResidual size of signal
* \param pResidual pointer to residual signal
* \param iSamplingRate sampling rate of signal
*/
void sms_filterHighPass(int sizeResidual, sfloat *pResidual, int iSamplingRate)
{
/* cutoff 800Hz */
static sfloat pFCoeff32k[10] = {0.814255, -3.25702, 4.88553, -3.25702,
0.814255, 1, -3.58973, 4.85128, -2.92405, 0.66301};
static sfloat pFCoeff36k[10] = {0.833098, -3.33239, 4.99859, -3.33239,
0.833098, 1, -3.63528, 4.97089, -3.02934,0.694052};
static sfloat pFCoeff40k[10] = {0.848475, -3.3939, 5.09085, -3.3939,
0.848475, 1, -3.67173, 5.068, -3.11597, 0.71991};
static sfloat pFCoeff441k[10] = {0.861554, -3.44622, 5.16932, -3.44622,
0.861554, 1, -3.70223, 5.15023, -3.19013, 0.742275};
static sfloat pFCoeff48k[10] = {0.872061, -3.48824, 5.23236, -3.48824,
0.872061, 1, -3.72641, 5.21605, -3.25002, 0.76049};
sfloat *pFCoeff, fSample = 0;
int i;
if(iSamplingRate <= 32000)
pFCoeff = pFCoeff32k;
else if(iSamplingRate <= 36000)
pFCoeff = pFCoeff36k;
else if(iSamplingRate <= 40000)
pFCoeff = pFCoeff40k;
else if(iSamplingRate <= 44100)
pFCoeff = pFCoeff441k;
else
pFCoeff = pFCoeff48k;
for(i = 0; i < sizeResidual; i++)
{
/* try to avoid underflow when there is nothing to filter */
if(i > 0 && fSample == 0 && pResidual[i] == 0)
return;
fSample = pResidual[i];
pResidual[i] = ZeroPoleFilter (&pFCoeff[0], &pFCoeff[5], 5, fSample);
}
}
/*! \brief a spectral filter
*
* filter each point of the current array by the surounding
* points using a triangular window
*
* \param pFArray two dimensional input array
* \param size1 vertical size of pFArray
* \param size2 horizontal size of pFArray
* \param pFOutArray output array of size size1
*/
void sms_filterArray(sfloat *pFArray, int size1, int size2, sfloat *pFOutArray)
{
int i, j, iPoint, iFrame, size2_2 = size2-2, size2_1 = size2-1;
sfloat *pFCurrentArray = pFArray + (size2_1) * size1;
sfloat fVal, fWeighting, fTotalWeighting, fTmpVal;
/* find the filtered envelope */
for(i = 0; i < size1; i++)
{
fVal = pFCurrentArray[i];
fTotalWeighting = 1;
/* filter by the surrounding points */
for(j = 1; j < (size2_2); j++)
{
fWeighting = (sfloat) size2 / (1+ j);
/* filter on the vertical dimension */
/* consider the lower points */
iPoint = i - (size2_1) + j;
if(iPoint >= 0)
{
fVal += pFCurrentArray[iPoint] * fWeighting;
fTotalWeighting += fWeighting;
}
/* consider the higher points */
iPoint = i + (size2_1) - j;
if(iPoint < size1)
{
fVal += pFCurrentArray[iPoint] * fWeighting;
fTotalWeighting += fWeighting;
}
/*filter on the horizontal dimension */
/* consider the previous points */
iFrame = j;
fTmpVal = pFArray[iFrame*size1 + i];
if(fTmpVal)
{
fVal += fTmpVal * fWeighting;
fTotalWeighting += fWeighting;
}
}
/* scale value by weighting */
pFOutArray[i] = fVal / fTotalWeighting;
}
}
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