clear all;
close all;
Fs=44100; N=8; f=Fs/N;
x=0:1:N*Fs-1;
t=x/Fs;
%y = chirp(t,0,N,f)+chirp(t,0,N,f/2);
y = chirp(t,0,N,f);
%y=cos(2*pi*t*f);
myx=(1:length(y))/length(y)*Fs;
plot(myx,abs(fft(y)));
sound(y, Fs); 
display("pôvodny chirp, ked doznie, stlac nieco"); pause;
M=16
figure;
yM=downsample(y,M);
myxM=(1:length(yM))/length(yM)*Fs/M;
plot(myxM,abs(fft(yM)));
sound(yM, Fs/M);display("M x podvzorkovaný chirp, ked doznie, stlac nieco"); pause;
figure;
yspec=fft(y);
keep=length(yspec)/(2*M)
for idx=1+keep:length(yspec)-keep
    yspec(uint32(idx))=0;
end
%plot(myx,abs(yspec));
%figure
ymax=real(ifft(yspec));
yMmax=downsample(ymax,M);
myx2=(1:length(yMmax))/length(yMmax)*Fs/M;
plot(myx2,abs(fft(yMmax)));
sound(real(yMmax), Fs/M);display("M x podvzorkovaný odfiltrovany chirp, ked doznie, stlac nieco"); pause;