Zero-Padding to the Next Higher Power of 2
Another reason we zero-pad is to be able to use a Cooley-Tukey FFT with any window length . When is not a power of , we append enough zeros to make the FFT size be a power of . In Matlab and Octave, the function nextpow2 returns the next higher power of 2 greater than or equal to its argument:
N = 2^nextpow2(M); % smallest M-compatible FFT size
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