Can't open .avs file in tmpegenc

[tai]

May be I'm stupid but I could not make tmpegenc to open .avs file when it refer to dv files. I could open .avs file when the .avi file the .avs file was referring to was not dv. I've got dv codec installed in my computer already. Here is the contents of my .avs file.

avisource("e:\scene0004.avi")
LetterBox(0,16)
BilinearResize(352, 288)

As you can see, there is nothing special in this file but when I opened it in tmpegenc, it gave me the message "File ... cannot open, or unsupported". I did try to change the priorities in VFAPI plug-in list though, but it didn't work either.
Could someone point out what the problem is please.

[tai]

This problem only happen when I use adaptec dv codec, mainconcept codec working fine. It's a bit pitty because adaptec dv codec seem to produce beter quality compare with mainconcept.
Using directshowsource command also fix the problem and product better quality compared with mainconcept dv codec!