Miglia Director's Cut Take 2, old VHS source - vertical sync offset problem

Question

I'm using a 20" iMac G5 and a Miglia Director's Cut Take 2 to import old family videos from VHS.
Some of these tapes are up to 21 years old, so they aren't exactly in the best shape. Still, I'm doing everything I can to get them in shape for capturing (including using the original tapes from the VHS camcorder, and exercising the tapes by fast forwarding them to the end then rewinding to the beginning before capturing).
Unfortunately, I'm having problems with the Director's Cut losing vertical synchronization whenever a worn out bit of the tape causes picture to be glitchy for a few seconds. The Director's Cut doesn't ever "fix" the sync on its own, until the next "glitch" in the tape happens to put it back in sync (or further out of sync).
This offset basically causes my captured video to have the bottom half of a frame on top, then the VHS head switch noise (which should be on the bottom of the video, not in the middle of it), then the top half of the next frame on the bottom. The VCR's on screen display, when I enable it, is offset too (this happens with both of the VCRs I tested). This means that the sync offset is NOT due to a VCR failing to properly syncronize the video (not to mention the unlikelyhood of that being the problem, due to the way that the VHS standard encodes pictures onto the tape).
What I find especially strange is that the vertical blanking interval doesn't appear in the middle of the video, right after the VHS head switch noise. The vertical blanking interval lasts for about 30 field lines (60 frame lines once the fields are combined in iMovie), so it should be quite prominent. This leads me to believe that the Director's Cut has managed to sucessfully capture the frames WITH proper vertical synchronization - which is then broken again somewhere between the Director's Cut and iMovie. My theory is that the Director's Cut isn't smart enough to change the read offset in its buffer between its analog to digital converter and its DV encoder. Another possibility: iMovie isn't doing the same thing between its Firewire interface and its DV decoder.
I can force the Director's Cut Take 2 to "restart" and regain sync by stopping input capture/monitoring in iMovie then starting it again, which also flips the DC2 between "Capture" and "Export" modes. Unfortunately, this is not a real solution for me - I don't want to babysit the computer while I'm importing all these long tapes. Plus, this causes me to lose a few seconds of video.
I've also tried to find ways to fix this problem using iMovie effect plugins. The closest I've got is using the "Vertical Hold" effect from the free Effects Pack 2 plugins (http://yorgle.cis.rit.edu/Software/iMovie/#dload) by Jerry Lawrence. Unfortunately, this plugin is really only useful for simulating, not correcting, vertical sync problems. It doesn't reference the previous or next frame in the DV file to get the top or bottom half of the picture. This results in a tearing effect, because, after I apply the filter, half of the picture is still from a different "frame" on the VHS tape.
Is my Director's Cut Take 2 defective, or is this normal behavior for the converter? If this is an unavoidable problem with the converter, is there any iMovie effect plugin that could correct it?
(If they would be helpful, I can post framegrabs of the DV file, and also framegrabs of the results of trying to use the "Vertical Hold" effect plugin.)
imac g5 (isight) 2.1ghz (base configuration), miglia director's cut take 2   Mac OS X (10.4.5)  

Answer 1

Hello, dbloom,
Is there a particular reason you are using Miglia for VHS conversion/capture?
I captured my old VHS tapes the way the other poster suggested by recording them onto DV tapes in my camcorder. (My computer setup is not convenient to do any direct connections from a VCR with a converter).Then, I imported the DV tapes to iMovie directly from the camcorder. I had no stoppages of imports/capture; the importing continued as long as my DV tapes, some of which were 80min.
This method also gives you a digital copy of the original VHS tape. I don't know about yours, but some of mine were getting to be pretty bad. I like having the DV tape of the raw footage to save. The DV versions are actually quite a bit better than the VHS tapes.
I have made iMovies of our family movies and photos of 15 years so far, burning the final edited versions to DVDs. I think I have made at least 40 movies so far, most of which are nearly 2hrs long. I also save the final movies back to DV tapes so that I have multiple backups of our family movies.
Just to add my 2 cents worth