[gst-devel] Changing width/height properties from within plugin

[Karol]

Hello,

I'm trying to write trivial plugin that does image rotation (90, 180, 
etc. degrees).  My question is - where should I change "width" and 
"height" properties?  I thought the proper place would be _chain() 
function(*) where I deal with buffer contents.  However, pipeline dies 
with internal error if I do that.  I guess I should handle that 
mysterious beast called caps negotiation? (specifically: _set_caps() 
function?)

(*) I'm using basic GstElement, not GstBaseTransform.

Thanks in advance.