鋸歯波 / Sawwave

function out = synth_sawwave(freq, ms, fs)
%SYNTH_SAWWAVE   Saw wave generator.
%   synth_sawwave(freq, ms, fs) generates a saw wave of specified
%   pitch and duration with unity amplitude.
%
%   freq - frequency of the tone in Hertz
%     ms - duration in milli-second
%     fs - sampling frequency in Hertz
%
%   2003-08-13 by MARUI Atsushi
%   2004-01-28 added direct method

method = 'build-up';
%method = 'direct';

switch lower(method)
  case {'build-up'}
    out = zeros(ceil(fs*ms/1000), 1);
    R = floor(fs/2 / freq); %number of sinewaves in a sawwave
    c = 2 * pi * (freq / fs);
    i = [1:size(out, 1)];
    for k=1:R
      out(i) = out(i) + (sin(c * (i-1) * k)/k)';
    endfor
  case {'direct'}
    t = 0:1/fs:ms/1000;
    out = sawtooth(2*pi*freq*t);
endswitch
out = normalize(out);