L=fwtlength(Ls,w,J);
fwtlength(Ls,w,J) returns the length of a Wavelet system that is long enough to expand a signal of length Ls. Please see the help on fwt for an explanation of the parameters w and J.
If the returned length is longer than the signal length, the signal will be zero-padded by fwt to length L.
In addition, the function accepts flags defining boundary extension technique as in fwt. The returned length can be longer than the signal length only in case of 'per' (periodic extension).