function X=extractPSD(x_train,startS,endS,wStep,wRange)

Fs=1;   % sampling frequency (seconds)

FS=128;

N=size(x_train,3);

sz=floor((endS-(startS+wRange))/wStep)+1;

X=zeros(sz*FS,2);

cn=0;

for i=1:N

    for sig=startS:wStep:endS-wRange

        sW=sig*FS+1;

        eW=(sig+wRange)*FS;

        C3Sig=x_train(sW:eW,1,i);

        C4Sig=x_train(sW:eW,3,i);

        [pxx3, ~] = pwelch(C3Sig,[],[],[],Fs);

        [pxx4, ~] = pwelch(C4Sig,[],[],[],Fs);

        cn=cn+1;

        X(cn,1)=sum(pxx3);

        X(cn,2)=sum(pxx4);

    end

end

end