Change divx3 to mpeg2 using avisynth

I need advice:

Someone with experience said to me:
"Use directshowsource with avisynth and open that in VirtualDub, then you can re-encode, cut, add filters whatever. it is the only way..."

I did create the AVS using this code:
DirectShowSource("video.avi", fps=23.976)

and I'm having an error when opening the AVS file in virtualdub:
"avi import filter error"

Can anyone show me how to do it right?

 

I used the avisource syntax instead and behold the following error:

"Avisynth open failure:
AviSource: Could not decompress frame 0
(c:\vid.avs, line1)"

The code is:
AviSource("video.avi")

Any Ideas?