musicdsp.org source code archive - WSInf

matlab/octave code for minblep table generation (click this to go back to the index)
References : Posted by dfl[at]ccrma[dot]stanford[dot]edu
Notes :
When I tested this code, it was running with each function in a separate file... so it might need some tweaking (endfunction statements?) if you try and
run it all as one file.
Enjoy!
PS There's a C++ version by Daniel Werner here.
http://www.experimentalscene.com/?type=2&id=1
Not sure if it the output is any different than my version.
(eg no thresholding in minphase calculation)
Code :
% Octave/Matlab code to generate a minblep table for bandlimited synthesis
%% original minblep technique described by Eli Brandt:
%% http://www.cs.cmu.edu/~eli/L/icmc01/hardsync.html
% (c) David Lowenfels 2004
% you may use this code freely to generate your tables,
% but please send me a free copy of the software that you
% make with it, or at least send me an email to say hello
% and put my name in the software credits :)
% (IIRC: mps and clipdb functions are from Julius Smith)
% usage:
% fc = dilation factor
% Nzc = number of zero crossings
% omega = oversampling factor
% thresh = dB threshold for minimum phase calc
mbtable = minblep( fc, Nzc, omega, thresh );
mblen = length( mbtable );
save -binary mbtable.mat mbtable ktable nzc mblen;
*********************************************
function [out] = minblep( fc, Nzc, omega, thresh )
out = filter( 1, [1 -1], minblip( fc, Nzc, omega, thresh ) );
len = length( out );
normal = mean( out( floor(len*0.7):len ) )
out = out / normal; %% normalize
%% now truncate so it ends at proper phase cycle for minimum discontinuity
thresh = 1e-6;
for i = len:-1:len-1000
% pause
a = out(i) - thresh - 1;
b = out(i-1) - thresh - 1;
%i
if( (abs(a) < thresh) & (a > b) )
break;
endif
endfor
%out = out';
out = out(1:i);
*********************************************
function [out] = minblip( fc, Nzc, omega, thresh )
if (nargin < 4 )
thresh = -100;
end
if (nargin < 3 )
omega = 64;
end
if (nargin < 2 )
Nzc = 16;
end
if (nargin < 1 )
fc = 0.9;
end
blip = sinctable( omega, Nzc, fc );
%% length(blip) must be nextpow2! (if fc < 1 );
mag = fft( blip );
out = real( ifft( mps( mag, thresh ) ) );
*********************************************
function [sm] = mps(s, thresh)
% [sm] = mps(s)
% create minimum-phase spectrum sm from complex spectrum s