repo2/atari_chips/pokeyv2/fir2_notch.m @ 1476
| 1454 | markw | pkg load signal;
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fsample = 48000;
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%fsample = 24000;
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%notches = [15600/4,15600/2,15600];
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cutoff = [15600,15600];
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cutoff_norm = cutoff/(fsample/2);
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%notches = load('notches');
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%notches = notches.freqs;
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notches = []
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linepal = 312*49.86;
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linentsc = 262*59.92;
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for i=1:8
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notches(end+1) = i*linepal/8;
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notches(end+1) = i*linentsc/8;
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end
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notches(end+1) = linepal/64;
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notches(end+1) = linentsc/64;
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notches = notches(notches<cutoff(2));
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notches_norm = notches/(fsample/2);
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steps = 10000;
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l=0;
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%thr = 0.0008;
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thr = 0.0016;
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%thr = 0.0032;
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for i = 0.0:1.0/steps:1.0
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l=l+1;
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pos(l) = i;
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val = min(((i-notches_norm).^2).^0.5);
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if val>thr
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func(l)= 1.0;
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else
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func(l) = 0.0;
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endif
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if i>cutoff_norm(2)
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func(l) = 0;
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continue;
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endif
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if i>cutoff_norm(1)
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cutoff_normd = cutoff_norm(2)-cutoff_norm(1);
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func(l) = (cutoff_norm(2)-i)/cutoff_normd;
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endif
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end
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fil_len = 2031;
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fil = fir2(fil_len,pos,func);
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bits = 16;
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range = (2^bits-2)/2;
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fil = round(fil*range)/range;
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[h,w] = freqz(fil,1,10000);
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f = pos;
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m = func;
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figure();
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subplot(121);
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plot(f,m,';target response;',w/pi,abs(h),';filter response;');
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subplot(122);
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plot(f,20*log10(m+1e-5),';target response (dB);',...
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w/pi,20*log10(abs(h)),';filter response (dB);');
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