[vdr] Vdr-xine OSD question

I am running vdr + vdr-xine plugin + coreavc + xine being output at 1080i to an HDTV as the only display. Is there a simple way to lock the OSD to the resolution of the output device such that the OSD is not rescaled when switching between SD and HD sources? I played with X-overlay, but that was not what I was after. If not, could it be done in the source somewhere or is the OSD anti-aliased and overlayed on the video before being sent to the output device (xine, in my case)? I've looked around quite a bit on the net but I guess my google-foo is failing me on this one. I just miss the rock-solid OSD of the FF card setup...

Thanks!