Commit 41748f04 by Earl Chew Committed by Erik de Castro Lopo

### Port David Robinson's equalloudfilt.m MATLAB script to scilab so that the...

```
Port David Robinson's equalloudfilt.m MATLAB script to scilab so that the ReplayGain filter settings can be generated using an OpenSource tool.
Signed-off-by: Earl Chew <earl_chew@yahoo.com>```
parent 0554a4ae
 // Equal Loudness Filter // // Adapted from original MATLAB code written by David Robinson // // http://replaygain.hydrogenaudio.org/proposal/equal_loudness.html // http://replaygain.hydrogenaudio.org/proposal/mfiles/equalloudfilt.m // ***************************************************************************** // Print Filter Coefficients // // This function takes a vector of filter tap settings, and prints // each tap setting from least significant to most significant. function c=printcoeff(p) c=coeff(p); c=c(\$:-1:1); for ix = 1:1:length(c) if ix > 1 printf(" ") end printf("%.14f", c(ix)); end endfunction // ***************************************************************************** // Equal Loudness Filter // // This function is adapted from David Robison's original MATLAB code. // Apart from changes to port it to scilab, the other change is to // use a single specification of the frequency points in the 80dB Equal // Loudness curve. // // The original code had different curves for different sampling // frequencies. This code dynamically computes the current data // points to use as determined by the Nyquist frequency. function [a1,b1,a2,b2]=equalloudfilt(fs); // Design a filter to match equal loudness curves // 9/7/2001 [%nargout,%nargin]=argn(0); // If the user hasn't specified a sampling frequency, use the CD default if %nargin<1 then fs=44100; end // Specify the 80 dB Equal Loudness curve EL80=[0,120;20,113;30,103;40,97;50,93;60,91;70,89;80,87;90,86; .. .. 100,85;200,78;300,76;400,76;500,76;600,76;700,77;800,78;900,79.5; .. .. 1000,80;1500,79;2000,77;2500,74;3000,71.5;3700,70;4000,70.5; .. 5000,74;6000,79;7000,84;8000,86;9000,86; .. .. 10000,85;12000,95;15000,110;20000,125;24000,140]; for ex = 1:1:length(EL80(:,1)) if EL80(ex,1) > fs/2 EL80 = [ EL80(1:ex-1,:); fs/2, EL80(ex-1,2) ]; break elseif EL80(ex,1) == fs/2 EL80 = EL80(1:ex,:); break end if ex == length(EL80(:,1)) EL80 = [ EL80(1:\$, :); fs/2, EL80(\$,2) ]; end end // convert frequency and amplitude of the equal loudness curve into format suitable for yulewalk f=EL80(:,1)./(fs/2); m=10.^((70-EL80(:,2))/20); // Use a MATLAB utility to design a best bit IIR filter [b1,a1]=yulewalk(10,f,m); // Add a 2nd order high pass filter at 150Hz to finish the job hz=iir(2,'hp','butt',[150/fs,0],[1e-3 1e-3]); b2=numer(hz); // b2=b2(\$:-1:1); a2=denom(hz); // a2=a2(\$:-1:1); endfunction // ***************************************************************************** // Generate Filter Taps // // Generate the filter taps for each of the desired frequencies. format('v', 16); freqs = [ 8000 11025 12000 16000 18900 22050 24000 .. 28000 32000 36000 37800 44100 48000 ]; for fx = 1:1:length(freqs) printf("\n%d\n", freqs(fx)); [a1,b1,a2,b2] = equalloudfilt(freqs(fx)); printf("{ "); bb=printcoeff(b1); printf(" }\n"); printf("{ "); aa=printcoeff(a1); printf(" }\n"); printf("{ "); printcoeff(b2); printf(" }\n"); printf("{ "); printcoeff(a2); printf(" }\n"); // freqz_fwd(bb,aa,1024,freqs(fx)); end quit
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