tomwalters@0: % method of class @signal
tomwalters@0: % 
tomwalters@0: %   INPUT VALUES:
tomwalters@0: %  
tomwalters@0: %   RETURN VALUE:
tomwalters@0: %
bleeck@3: % This external file is included as part of the 'aim-mat' distribution package
bleeck@3: % (c) 2011, University of Southampton
bleeck@3: % Maintained by Stefan Bleeck (bleeck@gmail.com)
bleeck@3: % download of current version is on the soundsoftware site: 
bleeck@3: % http://code.soundsoftware.ac.uk/projects/aimmat
bleeck@3: % documentation and everything is on http://www.acousticscale.org
bleeck@3: 
tomwalters@0: 
tomwalters@0: function sig=highpass(sig,frequency,stopband,ripple,stopbandatten)
tomwalters@0: % hack for an phase true lowpassfilter with cutoff at frequency
tomwalters@0: % used is a ButterworthFilter
tomwalters@0: 
tomwalters@0: if nargin < 5
tomwalters@0:     stopbandatten=60; % in dB - how many dB the signal is reduced in the stopband at least
tomwalters@0: end
tomwalters@0: if nargin < 4
tomwalters@0:     ripple=1; % in dB = ripple in the passband
tomwalters@0: end
tomwalters@0: if nargin <3
tomwalters@0:     stopband=frequency/2; % eine Oktave drunter
tomwalters@0: end
tomwalters@0: 
tomwalters@0: nyquist=getsr(sig)/2;
tomwalters@0: fre_low=frequency;
tomwalters@0: 
tomwalters@0: % passband
tomwalters@0: wp=[fre_low/nyquist 0.98];
tomwalters@0: 
tomwalters@0: % stopband
tomwalters@0: ws=[(fre_low-stopband)/nyquist 0.99];
tomwalters@0: 
tomwalters@0: % Finde raus, wieviel Punkte der Filter dafür haben muss
tomwalters@0: [n,Wn] = buttord(wp,ws,ripple,stopbandatten);
tomwalters@0: % Berechne den IIR-Filter
tomwalters@0: [b,a] = butter(n,Wn);
tomwalters@0: 
tomwalters@0: % testen:
tomwalters@0: % freqz(b,a,512,getsr(sig));
tomwalters@0: 
tomwalters@0: vals=sig.werte;
tomwalters@0: nvals = filtfilt(b,a,vals);
tomwalters@0: sig.werte=nvals;