[Scopeapp-cvs]scopeapp/src SpectrumView.h,1.8,1.9 SpectrumView.m,1.13,1.14

[<sco...@li...>]

Update of /cvsroot/scopeapp/scopeapp/src
In directory sc8-pr-cvs1:/tmp/cvs-serv1302/src

Modified Files:
	SpectrumView.h SpectrumView.m 
Log Message:
Implemented several windowing functions (Bartlett, Blackman, Hamming, Hann (aka
Hanning), Welch). Change scaling again; FFT results are divided by the area of
the window function (which is N for the rectangular window). 


Index: SpectrumView.h
===================================================================
RCS file: /cvsroot/scopeapp/scopeapp/src/SpectrumView.h,v
retrieving revision 1.8
retrieving revision 1.9
diff -C2 -d -r1.8 -r1.9
*** SpectrumView.h	19 Feb 2003 06:08:43 -0000	1.8
--- SpectrumView.h	20 Feb 2003 02:22:58 -0000	1.9
***************
*** 37,40 ****
--- 37,45 ----
  typedef enum WindowType {
  	eWindowRectangular = 0,
+ 	eWindowBartlett,
+ 	eWindowHann,
+ 	eWindowHamming,
+ 	eWindowBlackman,
+ 	eWindowWelch,
  } WindowType;
  
***************
*** 83,86 ****
--- 88,92 ----
  	NSData* myWindowFactors;
  	WindowType myWindowType;
+ 	float myWindowArea;
  	NSLock* mySavedDataLock;
  }

Index: SpectrumView.m
===================================================================
RCS file: /cvsroot/scopeapp/scopeapp/src/SpectrumView.m,v
retrieving revision 1.13
retrieving revision 1.14
diff -C2 -d -r1.13 -r1.14
*** SpectrumView.m	19 Feb 2003 11:01:26 -0000	1.13
--- SpectrumView.m	20 Feb 2003 02:22:58 -0000	1.14
***************
*** 114,117 ****
--- 114,119 ----
  		myFFTSetup = create_fftsetup(log2n, kFFTRadix2);
  
+ 		[self recalculateWindowWithSize: n];
+ 
  		if(wasDrawing) [self startDrawing];
  	} else {
***************
*** 214,218 ****
  
  	// apply scaling factor
! 	scale = 1.0 / length;
  	vsmul(real, 1, &scale, real, 1, length / 2);
  	vsmul(imag, 1, &scale, imag, 1, length / 2);
--- 216,224 ----
  
  	// apply scaling factor
! 	// I'm not sure that this is correct, but it gives correct results for
! 	// a wave with a power of 2 number of samples per cycle and
! 	// approximately correct (better than rectangular window) results for
! 	// other frequencies.
! 	scale = 1.0 / myWindowArea;
  	vsmul(real, 1, &scale, real, 1, length / 2);
  	vsmul(imag, 1, &scale, imag, 1, length / 2);
***************
*** 253,257 ****
--- 259,270 ----
  	int i, count = [data length] / sizeof(float);
  	
+ 	if(myWindowFactors == nil ||
+ 		[data length] != [myWindowFactors length])
+ 	{
+ 		[self recalculateWindowWithSize: count];
+ 	}
+ 
  	if(myWindowType == eWindowRectangular) {
+ 		// take a shortcut...
  		return data;
  	}
***************
*** 259,271 ****
  	newData = malloc([data length]);
  	oldData = [data bytes];
  
  	[mySavedDataLock lock];
  
- 	if([data length] != [myWindowFactors length])
- 	{
- 		[self recalculateWindowWithSize: count];
- 	}
- 	factors = [myWindowFactors bytes];
- 	
  #ifdef __APPLE__
  #pragma unused(i)
--- 272,279 ----
  	newData = malloc([data length]);
  	oldData = [data bytes];
+ 	factors = [myWindowFactors bytes];
  
  	[mySavedDataLock lock];
  
  #ifdef __APPLE__
  #pragma unused(i)
***************
*** 570,573 ****
--- 578,582 ----
  {
  	float* data;
+ 	int i;
  
  	if(myWindowFactors != nil) {
***************
*** 577,587 ****
--- 586,633 ----
  	if(myWindowType == eWindowRectangular) {
  		myWindowFactors = nil;
+ 		myWindowArea = length;
  		return self;
  	}
  
  	data = malloc(length * sizeof(float));
+ 	myWindowArea = 0;
  
  	switch(myWindowType)
  	{
+ 	case eWindowBartlett:
+ 		for(i=0; i<length/2; i++) {
+ 			data[i] = (2.0 * i) / (length - 1);
+ 			myWindowArea += data[i];
+ 		}
+ 		for(i=length/2; i<length; i++) {
+ 			data[i] = (2.0 * (length - i - 1)) / (length - 1);
+ 			myWindowArea += data[i];
+ 		}
+ 		break;
+ 	case eWindowHann:
+ 		for(i=0; i<length; i++) {
+ 			data[i] = 0.5 * (1 - cos(2*M_PI*((float)i / (length - 1))));
+ 			myWindowArea += data[i];
+ 		}
+ 		break;
+ 	case eWindowHamming:
+ 		for(i=0; i<length; i++) {
+ 			data[i] = 0.54 - (0.46*cos(2*M_PI*((float)i / (length - 1))));
+ 			myWindowArea += data[i];
+ 		}
+ 		break;
+ 	case eWindowBlackman:
+ 		for(i=0; i<length; i++) {
+ 			data[i] = 0.42 - (0.5*cos(2*M_PI*((float)i / (length - 1)))) +
+ 				(0.08*cos(4*M_PI*((float)i / (length - 1))));
+ 			myWindowArea += data[i];
+ 		}
+ 		break;
+ 	case eWindowWelch:
+ 		for(i=0; i<length; i++) {
+ 			data[i] = 1 - pow(((float)i - (length/2))/(length/2), 2);
+ 			myWindowArea += data[i];
+ 		}
+ 		break;
  	default:	
  		NSLog(@"-[SpectrumView recalculateWindowWithSize:]: unknown window type");