I tried to encode a video using VirtualDub with Avisynth filter but I got an error. I open video on VD (VirtualDub) and then run the script on it File<Run script but I got error:
Error during script execution at line 1, column 21: Variable 'LoadPlugin' not found LoadPlugin<!>(E:\filter.dll)
Looks like you are not doing the YV12 conversion on the source before running the plugin. That is my guess. Or you do not have AVIsynth 2.5. Those are know limitations posted in the documentation you had in the zip.
LoadPlugin("E:\AddGrain.dll")
A = AviSource("E:\movie.avi")
ConvertToYV12(A)
AddGrain (20, 0, 0)
I can't remember if you need to create the variable or not. Maybe this