Hi, the man page states that the parameter aspect in -lavcopts must be given in the form aspect=<x.x/y.y> Example: aspect=16.0/9.0 This isn't true, instead is must be given as d/d (16/9 or 4/3) or as a float (1.334 or 1.78) This is a case when RTFM doesn't apply, maybe a new acronym RTFM/C (M/C= manual or code) is appropriate:)