tns.c

《Visual C++小波变换技术与工程实践》作者：靳济芳。书上的代码。第3章：语音的去噪处理

	
	
	/* Perform filtering for each window */
	for(w=0;w<numberOfWindows;w++) 
	{
		TnsWindowData* windowData = &tnsInfo->windowData[w];
		TnsFilterData* tnsFilter = windowData->tnsFilter;
		
		startIndex = w * windowSize + sfbOffsetTable[startBand];
		length = sfbOffsetTable[stopBand] - sfbOffsetTable[startBand];
		
		if (tnsInfo->tnsDataPresent  &&  windowData->numFilters) {  /* Use TNS */
			TnsFilter(length,&spec[startIndex],tnsFilter);   
		}
	}
}


/*****************************************************/
/* TnsFilter:                                        */
/*   Filter the given spec with specified length     */
/*   using the coefficients specified in filter.     */
/*   Not that the order and direction are specified  */
/*   withing the TNS_FILTER_DATA structure.          */
/*****************************************************/
static void TnsFilter(int length,double* spec,TnsFilterData* filter)
{
	int i,j,k=0;
	int order=filter->order;
	double* a=filter->aCoeffs;

	/* Determine loop parameters for given direction */
	if (filter->direction) {

		/* Startup, initial state is zero */
		for (i=length-2;i>(length-1-order);i--) {
			k++;
			for (j=1;j<=k;j++) {
				spec[i]-=spec[i+j]*a[j];
			}
		}
		
		/* Now filter completely inplace */
		for	(i=length-1-order;i>=0;i--) {
			for (j=1;j<=order;j++) {
				spec[i]-=spec[i+j]*a[j];
			}
		}


	} else {

		/* Startup, initial state is zero */
		for (i=1;i<order;i++) {
			for (j=1;j<=i;j++) {
				spec[i]-=spec[i-j]*a[j];
			}
		}
		
		/* Now filter completely inplace */
		for	(i=order;i<length;i++) {
			for (j=1;j<=order;j++) {
				spec[i]-=spec[i-j]*a[j];
			}
		}
	}
}


/********************************************************/
/* TnsInvFilter:                                        */
/*   Inverse filter the given spec with specified       */
/*   length using the coefficients specified in filter. */
/*   Not that the order and direction are specified     */
/*   withing the TNS_FILTER_DATA structure.             */
/********************************************************/
static void TnsInvFilter(int length,double* spec,TnsFilterData* filter)
{
	int i,j,k=0;
	int order=filter->order;
	double* a=filter->aCoeffs;
	double* temp;

    temp = (double *)AllocMemory(length * sizeof (double));

	/* Determine loop parameters for given direction */
	if (filter->direction) {

		/* Startup, initial state is zero */
		temp[length-1]=spec[length-1];
		for (i=length-2;i>(length-1-order);i--) {
			temp[i]=spec[i];
			k++;
			for (j=1;j<=k;j++) {
				spec[i]+=temp[i+j]*a[j];
			}
		}
		
		/* Now filter the rest */
		for	(i=length-1-order;i>=0;i--) {
			temp[i]=spec[i];
			for (j=1;j<=order;j++) {
				spec[i]+=temp[i+j]*a[j];
			}
		}


	} else {

		/* Startup, initial state is zero */
		temp[0]=spec[0];
		for (i=1;i<order;i++) {
			temp[i]=spec[i];
			for (j=1;j<=i;j++) {
				spec[i]+=temp[i-j]*a[j];
			}
		}
		
		/* Now filter the rest */
		for	(i=order;i<length;i++) {
			temp[i]=spec[i];
			for (j=1;j<=order;j++) {
				spec[i]+=temp[i-j]*a[j];
			}
		}
	}
	if (temp) FreeMemory(temp);
}





/*****************************************************/
/* TruncateCoeffs:                                   */
/*   Truncate the given reflection coeffs by zeroing */
/*   coefficients in the tail with absolute value    */
/*   less than the specified threshold.  Return the  */
/*   truncated filter order.                         */
/*****************************************************/
static int TruncateCoeffs(int fOrder,double threshold,double* kArray)
{
	int i;

	for (i = fOrder; i >= 0; i--) {
		kArray[i] = (fabs(kArray[i])>threshold) ? kArray[i] : 0.0;
		if (kArray[i]!=0.0) return i;
	}

	return 0;
}

/*****************************************************/
/* QuantizeReflectionCoeffs:                         */
/*   Quantize the given array of reflection coeffs   */
/*   to the specified resolution in bits.            */
/*****************************************************/
static void QuantizeReflectionCoeffs(int fOrder,
							  int coeffRes,
							  double* kArray,
							  int* indexArray)
{
	double iqfac,iqfac_m;
	int i;

	iqfac = ((1<<(coeffRes-1))-0.5)/(M_PI/2);
	iqfac_m = ((1<<(coeffRes-1))+0.5)/(M_PI/2);

	/* Quantize and inverse quantize */
	for (i=1;i<=fOrder;i++) {
		indexArray[i] = (int)(0.5+(asin(kArray[i])*((kArray[i]>=0)?iqfac:iqfac_m)));
		kArray[i] = sin((double)indexArray[i]/((indexArray[i]>=0)?iqfac:iqfac_m));
	}
}

/*****************************************************/
/* Autocorrelation,                                  */
/*   Compute the autocorrelation function            */
/*   estimate for the given data.                    */
/*****************************************************/
static void Autocorrelation(int maxOrder,        /* Maximum autocorr order */
					 int dataSize,		  /* Size of the data array */
					 double* data,		  /* Data array */
					 double* rArray)  	  /* Autocorrelation array */
{
	int order,index;

	for (order=0;order<=maxOrder;order++) {
		rArray[order]=0.0;
		for (index=0;index<dataSize;index++) {
			rArray[order]+=data[index]*data[index+order];
		}
		dataSize--;
	}
}



/*****************************************************/
/* LevinsonDurbin:                                   */
/*   Compute the reflection coefficients for the     */
/*   given data using LevinsonDurbin recursion.      */
/*   Return the prediction gain.                     */
/*****************************************************/
static double LevinsonDurbin(int fOrder,          /* Filter order */
					  int dataSize,		   /* Size of the data array */
					  double* data,		   /* Data array */
					  double* kArray)  	   /* Reflection coeff array */
{
	int order,i;
	double signal;
	double error, kTemp;				/* Prediction error */
	double aArray1[TNS_MAX_ORDER+1];	/* Predictor coeff array */
	double aArray2[TNS_MAX_ORDER+1];	/* Predictor coeff array 2 */
	double rArray[TNS_MAX_ORDER+1];		/* Autocorrelation coeffs */
	double* aPtr = aArray1;				/* Ptr to aArray1 */
	double* aLastPtr = aArray2;			/* Ptr to aArray2 */
	double* aTemp;

	/* Compute autocorrelation coefficients */
	Autocorrelation(fOrder,dataSize,data,rArray);
	signal=rArray[0];	/* signal energy */

	/* Set up pointers to current and last iteration */ 
	/* predictor coefficients.						 */
	aPtr = aArray1;
	aLastPtr = aArray2;
	/* If there is no signal energy, return */
	if (!signal) {
		kArray[0]=1.0;
		for (order=1;order<=fOrder;order++) {
			kArray[order]=0.0;
		}
		return 0;

	} else {

		/* Set up first iteration */
		kArray[0]=1.0;
		aPtr[0]=1.0;		/* Ptr to predictor coeffs, current iteration*/
		aLastPtr[0]=1.0;	/* Ptr to predictor coeffs, last iteration */
		error=rArray[0];

		/* Now perform recursion */
		for (order=1;order<=fOrder;order++) {
			kTemp = aLastPtr[0]*rArray[order-0];
			for (i=1;i<order;i++) {
				kTemp += aLastPtr[i]*rArray[order-i];
			}
			kTemp = -kTemp/error;
			kArray[order]=kTemp;
			aPtr[order]=kTemp;
			for (i=1;i<order;i++) {
				aPtr[i] = aLastPtr[i] + kTemp*aLastPtr[order-i];
			}
			error = error * (1 - kTemp*kTemp);
			
			/* Now make current iteration the last one */
			aTemp=aLastPtr;
			aLastPtr=aPtr;		/* Current becomes last */
			aPtr=aTemp;			/* Last becomes current */
		}
		return signal/error;	/* return the gain */
	}
}


/*****************************************************/
/* StepUp:                                           */
/*   Convert reflection coefficients into            */
/*   predictor coefficients.                         */
/*****************************************************/
static void StepUp(int fOrder,double* kArray,double* aArray)
{
	double aTemp[TNS_MAX_ORDER+2];
	int i,order;

	aArray[0]=1.0;
	aTemp[0]=1.0;
	for (order=1;order<=fOrder;order++) {
		aArray[order]=0.0;
		for (i=1;i<=order;i++) {
			aTemp[i] = aArray[i] + kArray[order]*aArray[order-i];
		}
		for (i=1;i<=order;i++) {
			aArray[i]=aTemp[i];
		}
	}
}