I need to play a GEO-MPEG4 codec...with VIRTUAL DUB!

Hi,

I need to play an avi file with Virtual Dub, encoded by a GEO-MPEG4 codec (Geovision cctv) ...
I can read that file with Windows Media Player or Nero, but not in VirtualDub... Is there a reason for you?
Please let me know,
Thank you very much,
SM