avi looks perfect one play, grainy the next ...

[Blackout]

hi, ive seen this problem before when playing a video tape, but when playing an avi file off my pc ? i captured a partically dodgy video VHS tape via Canopus ADVC100 . It looked good going down. when playing the avi back some times it looks perfect, some times it looks grainy and flecked like a bad vhs tape. i cant get a decent render out of Vegas for this file.! even when i jump around on the timeline and play the same scene, sometimes it looks fine and then it seems there is a frame confusion for another play and it looks grainy on the exact same scene. im guessing its a field order confusion problem but i dont get why it should be different every time for the same avi file and scene....this is the same data file its feeding from every time.

how do i get a clean render out of this file?

many thanks,
Blackout

[Blackout]

after much research i figured this out myself. Sony Vegas was not gonna save my ass. Cue the savior of all video Virtualdub. It turns out the upper field was filthy dirty and the lower field was clean as a whistle. ive never seen this on a video file before. anyways the deinterlace in Virtualdub allows you to choose to dump one of the fields and i dumped the upper field. video plays clean now. (abeit slightly less smooth of course). but a hell of a lot more watchable now and stable. a bit of sharpening and noise reduction and it looks almost like a miracle extraction.

cheers,
Blackout