comparison util/matlab_midi/synth.m @ 81:a30e8bd6d948

matlab_midi scripts

+function y=synth(freq,dur,amp,Fs,type)
+% y=synth(freq,dur,amp,Fs,type)
+%
+% Synthesize a single note
+%
+% Inputs:
+%  freq - frequency in Hz
+%  dur - duration in seconds
+%  amp - Amplitude in range [0,1]
+%  Fs -  sampling frequency in Hz
+%  type - string to select synthesis type
+%         current options: 'fm', 'sine', or 'saw'
+
+% Copyright (c) 2009 Ken Schutte
+% more info at: http://www.kenschutte.com/midi
+
+if nargin<5
+  error('Five arguments required for synth()');
+end
+
+N = floor(dur*Fs);
+
+if N == 0
+  warning('Note with zero duration.');
+  y = [];
+  return;
+
+elseif N < 0
+  warning('Note with negative duration. Skipping.');
+  y = [];
+  return;
+end
+
+n=0:N-1;
+if (strcmp(type,'sine'))
+  y = amp.*sin(2*pi*n*freq/Fs);
+
+elseif (strcmp(type,'saw'))
+
+  T = (1/freq)*Fs;     % period in fractional samples
+  ramp = (0:(N-1))/T;
+  y = ramp-fix(ramp);
+  y = amp.*y;
+  y = y - mean(y);
+
+elseif (strcmp(type,'fm'))
+
+  t = 0:(1/Fs):dur;
+  envel = interp1([0 dur/6 dur/3 dur/5 dur], [0 1 .75 .6 0], 0:(1/Fs):dur);
+  I_env = 5.*envel;
+  y = envel.*sin(2.*pi.*freq.*t + I_env.*sin(2.*pi.*freq.*t));
+  
+else
+  error('Unknown synthesis type');
+end
+
+% smooth edges w/ 10ms ramp
+if (dur > .02)
+  L = 2*fix(.01*Fs)+1;  % L odd
+  ramp = bartlett(L)';  % odd length
+  L = ceil(L/2);
+  y(1:L) = y(1:L) .* ramp(1:L);
+  y(end-L+1:end) = y(end-L+1:end) .* ramp(end-L+1:end);
+end