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 {
    [self addObserver:self forKeyPath:@"Q" options:0 context:nil];
    [self addObserver:self forKeyPath:@"cornerFrequency" options:0 context:nil];
    return self;
}

- (void)observeValueForKeyPath:(NSString*)keyPath
                      ofObject:(id)object
                        change:(NSDictionary*)change
                       context:(void*)context
{
    if (
            [keyPath isEqualToString:@"Q"] || 
            [keyPath isEqualToString:@"cornerFrequency"]
        ) {
        [self calculateCoefficients]; 
    }
    
    else {
        [super observeValueForKeyPath:keyPath
                             ofObject:object
                               change:change
                              context:context];
    }
}
         
- (void) calculateCoefficients {
    if (cornerFrequency !== nil) {
        [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