In PMVP you can look at the file details - (media info)
Virtualdub works best with raw, uncompressed AVI files. Going from one compressed file and trying to compress it further will not produce good results.
Check out another example
here of a test file. Capture and compression details at the page.
I now have a Canopus ADVC-100 and hope to post more examples and rework the example. I have many, many hours of Hi8 tape to review!
Hope this helps,
Jeff