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1 % tri_filterbank_aa - Bank of anti-aliased triangular filters
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2 %
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3 % tri_filterbank_aa ::
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4 % E:[[M+2]->nonneg] ~'array of filter edge frequencies',
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5 % F:[[N]] ~'array of bin frequencies for input spectra'
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6 % -> [[M,N]] ~'matrix to multiply by input spectra'.
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7
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8 function W=tri_filterbank_aa(fb_edges,fmap)
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9 bins = buffer(edges(fmap),2,1,'nodelay');
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10 M = length(fb_edges)-2; % total number of filters to prepare
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11 W = zeros(M,size(bins,2));
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12 for i=1:M
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13 W(i,:) = olap_up(bins,fb_edges(i:i+1)) + olap_dn(bins,fb_edges(i+1:i+2));
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14 end
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15 W=sparse(W);
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16 end
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17
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18 function y=olap_up(bands,seg), [lx,cx]=intersect(bands,seg); y=lx.*(cx-seg(1))./(seg(2)-seg(1)); end
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19 function y=olap_dn(bands,seg), [lx,cx]=intersect(bands,seg); y=lx.*(seg(2)-cx)./(seg(2)-seg(1)); end
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20 function [lens,centres]=intersect(i1,i2),
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21 ivals=[max(i1(1,:),i2(1));min(i1(2,:),i2(2))]; % intersect intervals
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22 lens=max(ivals(2,:)-ivals(1,:),0); % positive lengths only
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23 centres=(ivals(2,:)+ivals(1,:))/2; % centres of intervals
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24 end
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