L=noshearlength(Ls,a,M,lt)
noshearlength(Ls,a,M,lt) computes the next larger transform length bigger or equal to Ls for which the shear algorithm does not require a frequency side shear for a non-separable Gabor system specified by a, M and lt.
This property makes computation of the canonical dual and tight Gabor windows gabdual and gabtight and the dgt for a full length window faster, if this transform length is choosen.