112 lines
3.4 KiB
C++
112 lines
3.4 KiB
C++
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/******************************************************************************
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* nid+.cpp *
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*---------*
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* I/O library functions for extended speech files (vapi format)
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*------------------------------------------------------------------------------
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* Copyright (C) 1999 Entropic, Inc
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* Copyright (C) 2000 Microsoft Corporation Date: 03/02/00
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* All Rights Reserved
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*
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********************************************************************* PACOG ***/
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#include "sigprocInt.h"
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#define FILTER_ORDER 40 /* Filter length 2*N+1 */
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/*****************************************************************************
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* sig *
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*----------*
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* Description:
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* Implements (-1)^(M-n). It might be better to implement it with
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* a macro. M is the filter order, so this function is simmetrical from M.
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******************************************************************* PACOG ***/
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static double Sign (int n)
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{
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if ((n-FILTER_ORDER)%2)
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{
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return -1.0;
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}
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return 1.0;
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}
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/*****************************************************************************
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* NonIntegerDelay *
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*-----------------*
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* Description:
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* Introduces a non integer delay by sinc interpolation.
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* The filter is simply truncated. Better response could be achieved by
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* using a different windowing function. So far, the response is adjusted
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* augmenting the number of points used in the interpolation.
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*
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* dDelay: 0<dDelay<1, fraction of a sampling period. No negative values
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* are allowed.
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******************************************************************* PACOG ***/
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int NonIntegerDelay (double* pdSamples, int iNumSamples, double dDelay)
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{
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double coefs[2*FILTER_ORDER+1];
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double* sampTemp;
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double constant;
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double acum;
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int firstCoef;
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int lastCoef;
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int i;
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int j;
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if (pdSamples && iNumSamples>0 && dDelay != 0.0 && fabs (dDelay) <1.0 )
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{
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//-- Allocate a temporary buffer to hold the pdSamples to filter.
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// The filtered samples go directly into the original buffer.
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if ( (sampTemp = new double [iNumSamples + 2*FILTER_ORDER+1]) == 0)
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{
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return 0;
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}
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memset (sampTemp, 0, sizeof(double)* FILTER_ORDER);
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memcpy (sampTemp+FILTER_ORDER, pdSamples, iNumSamples * sizeof (*pdSamples));
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memset (sampTemp+iNumSamples+FILTER_ORDER, 0, sizeof(double)* FILTER_ORDER);
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// Set up the filter. The amplitude constant does not depend
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// on the sign of dDelay (sin(-x)= -sin(x))
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constant= fabs( sin(M_PI*dDelay)/M_PI );
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// Without windowing, the coefs are samples of abs(1/x)
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coefs[FILTER_ORDER]=1.0/fabs(dDelay);
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if (dDelay>0.0)
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{
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for (j=1;j<=FILTER_ORDER;j++)
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{
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coefs[FILTER_ORDER+j] = -Sign(j) / (j-(double)dDelay);
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coefs[FILTER_ORDER-j] = Sign(j) / (j+(double)dDelay);
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}
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firstCoef=1;
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lastCoef=2*FILTER_ORDER;
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}
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else
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{
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for (j=1;j<=FILTER_ORDER;j++)
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{
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coefs[FILTER_ORDER-j] = -Sign(j) / (j+(double)dDelay);
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coefs[FILTER_ORDER+j] = Sign(j) / (j-(double)dDelay);
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}
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firstCoef = 0;
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lastCoef = 2*FILTER_ORDER-1;
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}
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for (i=0;i<iNumSamples;i++)
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{
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acum = 0.0;
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for (j=firstCoef; j<=lastCoef; j++ )
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{
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acum += sampTemp[i+j] * coefs[j];
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}
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pdSamples[i]=constant*acum;
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}
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delete[] sampTemp;
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}
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return 1;
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}
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