videocrop not controllable by GstController

I'm currently working at the project VOC2MIX which we just used at Chaos Communication Congress 36c3. So just a small thank you for GStreamer which we rely on. It mostly worked well!

We used a lecture composite where we crop the speakers camera picture so that it fits beside the slides.

We first tried to use videocrop to do the cropping but that didn't work together with GstController which we need to do transitions (where cropping also changes softly between the different composites). We could set initial cropping but changing the crop via GstController did nothing.

At last we decided to use videobox which accepts the GstController updates and worked but brought us another problem with random video distortion in some cases. But this is another bug.

But because videobox didn't work so well, I would like to replace it with videocrop again to see if there are the same problems.

So I would like videocrop to be usable with GstController in future.