Vertical jitter / alignment issue: how frequent must it be to fix?

[ThumperStrauss]

I changed my workflow

• from: JVC HR-S3910U (no line TBC) -- Panasonic ES-15 -- Datavideo DVK-200 -- AIW 9600XT
• to: JVC HR-DVS3U (line TBC) - Datavideo DVK-200 -- AIW 9600XT

I re-captured a VHS tape (television recording in SP mode) with the new workflow to see if it was any different. I haven't reviewed all 2 hours, but I spotted three instances where there is vertical jitter (I think that is the term) in the new workflow. See attachment for example. The entire image moves up (or down) in the frame. I reviewed the raw video from the original workflow and there is no vertical jitter in those places, and nowhere else.

For the record, the JVC DVS3U settings has video-calibration ON, TBC/NR ON, and Video Stabilizer OFF (because it can't be ON if TBC/NR is ON).

QUESTIONS

1. In my original workflow, the JVC didn't have TBC, so I'm pretty sure I had the Stabilizer ON. Would the Stabilizer more or less guarantee no vertical jitter on a VHS tape from a TV recording in SP mode?

2. Or is this very intermittent vertical jitter (still looking for other instances on the tape...) an alignment issue and something I need to to physically adjust on the tape head? I ask because if it was an alignment issue, how much vertical jitter instances would one see? Would it be more-or-less constant? Or rare like I seem to be seeing.

[ThumperStrauss]

UPDATE: I did some more tests and discovered the following:

The vertical jitter is probably being triggered by the Datavideo DVK-200. (I had added it to the workflow because of its (weak) frame TBC powers to help keep the audio and video in sync over long periods.)

I did a series of tests, which you can see in the attached video, including:

• JVC DVS3U (line TBC ON, stabilization OFF) — Datavideo DVK-200 — AIW 9600XT = VERTICAL JITTER
• JVC DVS3U (line TBC OFF, stabilization ON) — Datavideo DVK-200 — AIW 9600XT = VERTICAL JITTER
• JVC DVS3U (line TBC OFF, stabilization ON) — AIW 9600XT = NO VERTICAL JITTER, BUT TEARING
• JVC DVS3U (line TBC ON, stabilization OFF) — AIW 9600XT = PERFECT
• JVC DVS3U (line TBC ON, stabilization OFF) — Panasonic ES15 — Datavideo DVK-200 — AIW 9600XT = PERFECT

In short, the results show that I cannot use the Datavideo DVK-200 without also using the Panasonic ES15. I guess this is what Lord Smurf meant when he said that the ES15 tames the DVK-200 and produces video it can handle. Lord Smurf also calls the line TBC in the ES15 very strong, which explains why the ES15 line TBC (and not the JVC DVS3U line TBC) is able to work well with the Datavideo DVK-200.

My next steps:

• I'll have to review the forum posts on whether to turn on TBC on the JVC, if I am using the ES15 in the workflow. I suppose the JVC DVS3U is better in other ways than a lower end JVC SVHS player, so I will continue to use it.
• I'll have to do some testing of long tapes to see if I can remove the Datavideo DVK-200 from the workflow without causing the audio video to go out of sync.

[latreche34]

Then just use the ES-15 only.

If the VCR's line TBC is not defective and turned on it should not give you audio sync provided that you have a good capture card not a chinese crap.

[ThumperStrauss]

I did another test using this workflow: JVC HR-DVS3-U (line TBC ON, stabilization OFF) — AIW 9600XT. I recorded six hours from an EP tape. The audio and video were in sync by the end of the six hours, however, VirtualDub1911 reported:

Frame inserted: 68
Frames dropped: 141

I got similar results with the JVC HR-DVS3-U, which I tested right after. I know that a fragmented hard drive might cause dropped frames, or having other apps open. But the 2TB data drive wasn't fragmented, and I use a Windows XP (Integral version) on a 1TB system drive, with no Internet, and no apps installed apart from VirtualDub1911, and the ATI apps.

The JVC line-TBC definitely cleans the image. But what I'm not certain of is whether a JVC line-TBC is supposed to prevent inserted and dropped frames, or whether it can't be relied upon for that, which where the frame TBC (Datavideo TBC-1000 or similar) comes in.

For the record, my timing settings that were selected during this capture were:

[X] Drop frames when captured frames are too close together
[X] Insert null frames when captured frames are too far apart
Null frame burst limit: 10
[X]Sync audio to video by resampling the audio to a faster of slower rate

[latreche34]

To get a perfect video/audio sync off course frames have to be inserted or dropped, Video is measured in frames and audio in KHz to avoid messing with changing audio frequency good capture cards drop or insert frames as it sees fit. 141 in 6 hrs is nothing, If you are dropping frames excessivly or due to other issues then that should be a concern but for timing purposes that's perfectly fine. As I always say, keep your workflow as simple as possible and don't add anything to it until a problem arises.

VCR line TBC has DNR so when it digizes lines it applies DNR while in the digital domain, It is not designed to fix VBI, though some advanced TBC's found on some pro capture devices do have lines and frames timing chip that fixes HBI and VBI together followed by a frame synchronizer to keep audio in sync and output the signal in its digital state via SDI.

[cbehr91]

If you are using both the ES15 and DVK in line you should disable the JVC TBC. The ES15+DVK pair are correcting line and frame-based timing errors.

I, too, have a DVS3U, and for my tapes the stabilizer does nothing. A jittery tape still jitters no matter what combination of settings I use or don't use. I have to use another VCR. It's the tape, not the VCR.

As for an alignment, I don't know. The head switching noise at the bottom of the picture is within the acceptable 10ish pixel range. Someone with more knowledge could probably tell if you if you need an alignment, but I would hasten to align it just to align it.

If you're using a external TBC or just the ES15 as passthru and still getting a ton of frame drops/inserts it's very likely system related. Disable backup processes, disconnect the capture machine from the internet, test different VirtualDub timing settings, etc. I know for old vets this is video capture 101, but when started I was still capturing to the C drive and was getting loads of frame drops/inserts with the proper requisite hardware. I had to put a second hard drive in and use that as the capture drive (boot Windows from C, capture to D). Again, I know that's video capture 101, but everyone was new at some point.

[hodgey]

The SM for this deck specifies the switching point should be 8 (+/- 0.5) lines before the vertical sync signal - that is on a self-recording/alignment tape though - on a pre-recorded tape or tape recorded in a different machine that may not match exactly. (I've seen commercial tapes where the switching point was way off too so can't really base it on that.) It doesn't look particularly off though, it's usually not something one needs to adjust unless you have swapped video head drums or similar. (I've only seen it been off otherwise on some older panasonic vcrs). In any case it's a pain to adjust on newer JVC decks as it requires the special very rare service remote because JVC decided to be annoying. (Don't know any other decks that require special service remotes for adjustment other than sony 8mm camcorder/vcrs, but not their VHS ones) If it's somehow very off it's possible to manually tweak it by rotating the drum stator but that's not really something you want to do unless there is a very good reason to, it looks fine here.

Video stabilizer is mainly useful for recordings when there are issues on the top of the frame, e.g on a bad tape dub, maybe from a bad/misaligned deck. What I believe it does something like blank out and insert a new vertical sync signal based on the switching point between the video heads (as you can see in linked the video I made a while back). Don't think it's all that useful on a good recording. On a few vcrs/camcorders this sort of thing was integraded with the tbc function - e.g on the late model jvc vhs camcorders with tbc, but on the JVC SVHS decks it's not.

[traal]

Have you repacked the tape (fast-forward all the way to the end until it rewinds itself back to the beginning) to make sure inconsistent tension isn't causing some of those inserted and dropped frames?