No, to open a simple mpeg (mpeg1) you dont need any plugins for Virtualdub .... there also exist a mpeg2 version of VirtualDub which knows how to open both .. mpeg1 and mpeg2 I use it everytime to "preview" my encodings cause for me its the only "previewer" which does show the picture in its "real" condition.
1. In Vdub open your m1v or mpeg, a message appears "parsing mpeg..."
2. Watch your movie and its condition ... is it squeezed (480x576(480))?
3. Go and "start frameserver" left below
4. Save the frameserving file as xxxxx.vdr (its importand to add the.vdr manually!)
5. Open your Avisynth script and change the source import line to the following:
AVISource("Your Frameserver File.vdr")
Followed by further filter routines as set.
This should work .........
and by the way this also brings me to an Idea! VMesquita!! We'll see