annotate util/matlab_midi/synth.m @ 247:ecce33192fcc tip

Added tag ver_2.1 for changeset cef4500b936f
author luisf <luis.figueira@eecs.qmul.ac.uk>
date Wed, 31 Oct 2012 12:24:44 +0000
parents a30e8bd6d948
children
rev   line source
ivan@81 1 function y=synth(freq,dur,amp,Fs,type)
ivan@81 2 % y=synth(freq,dur,amp,Fs,type)
ivan@81 3 %
ivan@81 4 % Synthesize a single note
ivan@81 5 %
ivan@81 6 % Inputs:
ivan@81 7 % freq - frequency in Hz
ivan@81 8 % dur - duration in seconds
ivan@81 9 % amp - Amplitude in range [0,1]
ivan@81 10 % Fs - sampling frequency in Hz
ivan@81 11 % type - string to select synthesis type
ivan@81 12 % current options: 'fm', 'sine', or 'saw'
ivan@81 13
ivan@81 14 % Copyright (c) 2009 Ken Schutte
ivan@81 15 % more info at: http://www.kenschutte.com/midi
ivan@81 16
ivan@81 17 if nargin<5
ivan@81 18 error('Five arguments required for synth()');
ivan@81 19 end
ivan@81 20
ivan@81 21 N = floor(dur*Fs);
ivan@81 22
ivan@81 23 if N == 0
ivan@81 24 warning('Note with zero duration.');
ivan@81 25 y = [];
ivan@81 26 return;
ivan@81 27
ivan@81 28 elseif N < 0
ivan@81 29 warning('Note with negative duration. Skipping.');
ivan@81 30 y = [];
ivan@81 31 return;
ivan@81 32 end
ivan@81 33
ivan@81 34 n=0:N-1;
ivan@81 35 if (strcmp(type,'sine'))
ivan@81 36 y = amp.*sin(2*pi*n*freq/Fs);
ivan@81 37
ivan@81 38 elseif (strcmp(type,'saw'))
ivan@81 39
ivan@81 40 T = (1/freq)*Fs; % period in fractional samples
ivan@81 41 ramp = (0:(N-1))/T;
ivan@81 42 y = ramp-fix(ramp);
ivan@81 43 y = amp.*y;
ivan@81 44 y = y - mean(y);
ivan@81 45
ivan@81 46 elseif (strcmp(type,'fm'))
ivan@81 47
ivan@81 48 t = 0:(1/Fs):dur;
ivan@81 49 envel = interp1([0 dur/6 dur/3 dur/5 dur], [0 1 .75 .6 0], 0:(1/Fs):dur);
ivan@81 50 I_env = 5.*envel;
ivan@81 51 y = envel.*sin(2.*pi.*freq.*t + I_env.*sin(2.*pi.*freq.*t));
ivan@81 52
ivan@81 53 else
ivan@81 54 error('Unknown synthesis type');
ivan@81 55 end
ivan@81 56
ivan@81 57 % smooth edges w/ 10ms ramp
ivan@81 58 if (dur > .02)
ivan@81 59 L = 2*fix(.01*Fs)+1; % L odd
ivan@81 60 ramp = bartlett(L)'; % odd length
ivan@81 61 L = ceil(L/2);
ivan@81 62 y(1:L) = y(1:L) .* ramp(1:L);
ivan@81 63 y(end-L+1:end) = y(end-L+1:end) .* ramp(end-L+1:end);
ivan@81 64 end