DDC in Matlab

Servus,

man merkt folgendes im dsp.DigitalDownConverter System object 
http://www.mathworks.com/help/dsp/ref/dsp.digitaldownconverter-class.html:

DecimationFactor klein -> Warnung: The filter design has not converged. 
Try increasing the passband ripple value, or decreasing the stopband 
attenuation.

DecimationFactor gross -> OK.

Ist das normal? Warum?

Owen