The idea is to be able to perform operations on a converted and scaled
stream in the appsink, but - depending on the result of the operations -
being also able to access the unmodified stream in there. Synchronization of
frames is important - there's no point in that if the original and scaled
frames do not share the same source frame.
Is there an easy way to do that in GStreamer, or should I move the convert
and scaling to the appsink and essentially handle that myself?