Interlace Jitter/Twitch, possible field order shift?

[FurrBear]

I'm trying to transfer a low-budget biker movie I'm inexplicably fond of from VHS to DVD. Unfortunately, it seems that the mastering of the tape was *really* badly done, and there's a recurring interlace-related problem I don't know how to fix. I've posted a 7.2MB DV AVI sample at http://www.dslextreme.com/users/furr/JitterSample.avi for anyone who wants a first hand look.

From what I've learned reading through this and other sites -- it *looks* to me like the field order is slipping back and forth in the original analog recording. This isn't apparent on a regular tv, of course, but becomes an issue for capturing.

Is it possible I'm losing individual fields, causing this problem? The tape wouldn't capture without many dropped frames until I got my AVT-8710 time-base corrector. I used the video capture utility that comes with Vegas 4 to do the capture. I'm using a Canopus ADVC-1394 card as my capture device.

(And yes -- I've been able to capture from other tapes and laserdiscs without having this problem. It's specific to this particular tape.)

I realize I could encode this at 352x240, but I'd prefer not to throw away that much resolution if I don't have to. I've only just begun to use VirtualDUB and AVIsynth, so please be patient with me if your suggested fixes involve those applications.

George

PS: I just went and tested video capture in VirtualDUB -- same problem.

[SLK001]

I can't view your file (no fourCC codec). I suspect you have a capture issue.

Doesn't your capture utility report on dropped frames?

[FurrBear]

I can't view your file (no fourCC codec). I suspect you have a capture issue.

It's a DV AVI; any DV playback codec should work.

But perhaps a clip is overkill; here's a still of the problem:



Remember -- it switches back and forth between being correct and this; if the ENTIRE capture were like this it would be pretty easy to fix.

I would agree that it could be a capture issue *for this tape*, but I've captured successfully from other VHS tapes, Beta tapes, and Laserdisc; I know my capture card/computer setup works generally.

Doesn't your capture utility report on dropped frames?

Yes, it does, and it didn't report any dropped frames. I'm just wondering if maybe because the tape's so badly out of spec (it won't capture without a lot of dropped frames unless I use the TBC) that perhaps the TBC is "splicing" around lost frames.

[FulciLives]

Well I downloaded the AVI and loaded it into VirtualDubMod and then frameserved it into TMPGEnc. I had to do this way as TMPGEnc would not accept the file directly.

Anyway I encoded it twice. Once using the NTSC DVD Template in WIZARD mode where it selected BOTTOM FIELD automatically.

When I played it out to my TV using my Hollywood Plus MPEG decoder card (essentially the same type of output had I burned it to a DVD-R and played it on a stand alone DVD player) I did see the JITTER and it does appear to be due to changing field order (which I saw in VirtualDubMod when I looked at the file in slow mo).

So then I did another two encodes with TMPGEnc again using the WIZARD MODE but with one I did DEINTERLACE with ODD FIELD and DEINTERLACE with EVEN FIELD.

Now this of course isn't the best method of deinterlace since it just discards one of the fields but the result was no more jitter when using ODD but when I used EVEN there still was no jitter but a "shift" of the title up and then down.

Please note I might have confused which was EVEN and which was ODD but I think it was the ODD one that looked good with no shifting.

So in short you might want to look into some deinterlacing methods.

- John "FulciLives" Coleman