Subtitler:During spotting stepping forward doesn t properly work

During spotting, stepping forward doesn't properly work. Sometimes works for 2 frames and then doesn't work anymore until JKL is used again and then the same happens.

Some QT movies from nonlinear editing applications contain internal informations which make stepping difficult. If you use Final Cut Pro, you should not export a Final Cut Pro movie (File:Export:Quicktime Movie with a FCP icon) but export a Quicktime movie (File:Export:Using Quicktime Conversion with a native Quicktime icon).