NVHPF.h

//
//  NVHighpassFilter.h
//  NVDSP
//
//  Created by Bart Olsthoorn on 18/05/2012.
//  Copyright (c) 2012 Bart Olsthoorn. All rights reserved.
//

#import "NVDSP.h"

@interface NVHighpassFilter : NVDSP

@property (nonatomic, assign, setter=setCornerFrequency:) float cornerFrequency;
@property (nonatomic, assign, setter=setQ:) float Q;

@end

NVHPF.mm

//
//  NVHighpassFilter.m
//  NVDSP
//
//  Created by Bart Olsthoorn on 18/05/2012.
//  Copyright (c) 2012 Bart Olsthoorn. All rights reserved.
//

#import "NVHighpassFilter.h"

@implementation NVHighpassFilter

@synthesize Q;
@synthesize cornerFrequency;

- (id) init {
    [super init];
    return self;
}

- (void) setQ:(float)_Q {
    Q = _Q;
    [self calculateCoefficients];
}

- (void) setCornerFrequency:(float)_cornerFrequency {
    cornerFrequency = _cornerFrequency;
    [self calculateCoefficients];
}
         
- (void) calculateCoefficients {
    if ((cornerFrequency != 0.0f) && (Q != 0.0f)) {
        [self intermediateVariables:cornerFrequency Q:Q];
        
        a0 = 1 + alpha;
        b0 = ((1 + omegaC)/2)      / a0;
        b1 = (-1*(1 + omegaC))     / a0;
        b2 = ((1 + omegaC)/2)      / a0;
        a1 = (-2 * omegaC)         / a0;
        a2 = (1 - alpha)           / a0;
    }
}

- (void) dealloc
{
    [super dealloc];
}

@end