load db10;
subplot(621);stem(db10);title('db10低通濾波器');grid;
qmfdb10=qmf(db10);
subplot(622);stem(qmfdb10);title('QMF低通濾波器');grid;
m=fft(db10);
mt=fft(qmfdb10);
freq=[1:length(db10)]/length(db10);
subplot(625);plot(freq,abs(m));
title('db10的轉(zhuǎn)換模式');grid;
subplot(626);plot(freq,abs(mt));
title('QMF db10的轉(zhuǎn)換模式');grid;
subplot(629);plot(freq,abs(m).^2+abs(mt).^2);
title('檢查db10和QMFdb10的QMF條件');grid;
xlabel('abs(fft(db10))^2+abs(fft(qmf(db10))^2=1');
df=[db10;qmfdb10]*sqrt(2);
id=df*df'