  The space mission CoRoT provides us with a large amount of high-duty cycle
long-duration observations. Mode fitting has proven to be efficient for the
complete and detailed analysis of the oscillation pattern, but remains time
consuming. Furthermore, the photometric background due to granulation severely
complicates the analysis. Therefore, we attempt to provide an alternative to
mode fitting, for the determination of large separations. With the envelope
autocorrelation function and a dedicated filter, it is possible to measure the
variation of the large separation independently for the ridges with even and
odd degrees. The method appears to be as accurate as the mode fitting. It can
be very easily implemented and is very rapid.
