VHS jitters with TBC turned on

[timmus]

How come when I play some 1990-vintage VHS tapes in my AG-1980 and turn on TBC, some of the footage has a slight amount of vertical jitter? It's like the frame randomly moves up about 1 or 2 pixels several times per second. When I turn off TBC, it goes away. Some of the footage does it, some of it doesn't.

Have you all seen anything like this? Does this mean that TBC is not always a good idea?

[victoriabears]

Over the 5 years of dvd conversion from vhs I have seen most things, and over processing is one of them.

If it works , don;t knock it

[orsetto]

Yes, it means TBC is not always a good idea.

Some tapes have stubborn combined issues that cannot be completely "fixed" or improved, you have to compromise and accept less than perfection. Generally this means turning the TBC off and tollerating a bit of horizontal noise or distortion in exchange for avoiding TBC-induced jitter. The AG1980 is less prone to jitter than comparable JVC or Mitsubishi models, but it does happen. Each VCR model has different abilities to switch its TBC and noise filters on or off, this can be very significant with some tapes which is why many of us have made the outlay to own both a Panasonic AG1980 and a JVC or Mitsubishi. Often a tape will play much better on one rather than the other.

[lordsmurf]

The AG1980 is less prone to jitter than comparable JVC or Mitsubishi models, but it does happen.

I don't notice the Panasonic doing it any less than the JVC models.

This scenario is briefly discussed here: http://www.digitalFAQ.com/guides/video/capture-playback-hardware.htm
Scroll to the bottom of the page for sample images and text.

[orsetto]

The Panasonic AG1980 is indeed less prone to the occasional "TBC induced jitter" problem, particularly with SLP tapes: thats the entire point of owning one. If it did not sometimes have a couple of performance advantages, none of us would bother owning it in addition to a JVC. Each machine has a "personality" which will be more or less suited to the task depending on the tape. Often its too subtle to worry about, other times its noticeable. The AG1980, for example, is less prone to the jitter issue but MORE prone to moire and other issues caused by its overpowering DNR, which cannot be turned off like its TBC. On the other hand its moire-prone DNR can give more pleasing results than a JVC in some cases: the JVC trades off very smooth filter output against a sometimes too-creamy appearance. Each has capabilities the other does not, it depends on the tape and interactions with your digitizing device. I can't work with only one, I need both machines. I wish this was not the case, because constant testing of which VCR is best for each tape gets extremely tedious and time consuming. Unfortunately no single VCR is 100% perfect for the entire range of tapes one might confront (A possible exception being the incredible JVC analog HDTV-VHS , rarer than rare and very expensive to recondition. If you get one ithats still operational, it plays back regular VHS so well it makes the SVHS Panasonics and JVCs look pathetic. Too bad they're so scarce and cranky, available only as ancient second-hand grey market imports.)

[timmus]

Yeah, I ran across another tape last night (SLP too) that started rolling (i.e. bad vertical sync, like on old TVs) when TBC was on. It makes no sense to me why the TBC would go haywire like that. Is there any specific technical issue that predisposes TBC to failure?

[robjv1]

Unfortunately no single VCR is 100% perfect for the entire range of tapes one might confront (A possible exception being the incredible JVC analog HDTV-VHS , rarer than rare and very expensive to recondition.

Regarding the original question (jitter with the TBC on) and applying it to these decks (JVC SR-W5U/W7U) unfortunately these decks don't reach perfection with it either. I think the better built transport mechanism prevents much of the jitter seen on some of the more cheaply made JVC decks -- but I still see that dreaded "up and down frame shift" with some videos with the TBC engaged. On high quality tapes, it's a frame here and there. On some tapes it's every couple of seconds, it just depends.

I *wish* somewhere, somebody had designed a deck (perhaps based on these JVC decks, which are mostly excellent machines) where you could toggle on and off or through a range, all the individual characteristics of the TBC and DNR. Wouldn't it be great to have a TBC/DNR VCR with user adjustable controls to tweak for individual tapes?

If you are pursuing perfection of eliminating jitter all together, combined with using the TBC for every other part of a tape where it works -- the only way I've found to get there (or near there) is to follow this (brute-force) protocol:

1. Buy a proc-amp

2. Dub your program tape (with the TBC engaged) to DVD, taking note of the proc-amp controls (write them down).

3. Watch the entire video and take note of the jitter issue where it occurs. (write down the time)

4. Redub the parts where your errors occurred, this time with the TBC off (and perhaps with a Panasonic ES-10 in-line to prevent jitter/wavy lines).

Be aware that when the JVC TBC goes from on to off, the saturation of the color changes, as well as the black level and brightness of the image. Compensate accordingly. I suppose you could do all the color matching on a computer as well, although I prefer to do it on the proc-amp since I have two monitors anyways.

5. Pull both versions into a NLE, and fix the bad parts with the other footage. If you're careful and match them well, the differences will be transparent.

Efficiency wise, it's the pits.... but you can eliminate the jittery TBC issue without eliminating the TBC entirely. Besides, weren't you going to watch your dub anyways at some point? Might as well fix it now and not when you pull the tape out in 20 years and no longer have the equipment to do it.

[vhelp]

I would also like to add to this issue, or should we really be calling it, phenomina, because that seems to be what it is currently because there are too many things that cause "jitter" (up or down, etc) and its just too mind boggling to tie it cause down to one variable.

My current vcr is the JVC S-VHS HR-S3910U since sept/2001. I've put many tapes through this machine over the years. But, I mostly stuck with one brand, Fuji. Some people spit at that brand, but i think that success depends early on in the vcr's life cycle, when you stick to one brand. I mostly stuck this one particular brand and model tape, and recorded almost everything in EP mode on them, unfortunately, analog cabletv which was very noisy but ancient history now.

At the moment, i am capturing my store bought commercial tapes. I have a few standard test tapes I use (because I bouht two copies of some of them) and i use these same tapes regulary.

One thing I have noticed over the last few dozen or so captures (when testing different capture card types) is that this phenomina known as jitter seems to find its place on these commercial tapes too. Not sure why they are there now all the sudden, but I have some theories.

I believe that these issues are all based on a product macrovision (MV) Pretty much everything we have, vcr, dvd recorder, captures cards, etc., all have some MV design built into them. And, whenever something close to MV is mistakenly perceived as such, all these units react according to their design, be it manipulating color, snow, noise, fading, rolling, jittering, etc. That also include the audio. My Star Trek vhs tapes have MV in the audio. When I try capturing my star trek Insurection tape, the audio is distored, almost like someone turned out the audio so loud that it distorts really bad, and that also effect how the capture accepts the source and processes, MV inducement properties or not. So, there are many things that cause pictures issues, including, jitter. So, if I put CaptureCard_A in and capture it, and then put my CaptureCard_B in and capture it, I will get differnt MV related effects. My movie, Contact jitters in one capture card but not in the other. There are so many variables. And it is very difficult to lock the issue(s) down into one cause. Sheesh, I thought I had a good system, vcr->advc->dvcam or vcr->dvcam, but recently, and to my surprise, as it turns out, this method adds (DV) macroblocks, so now its back to uncompressed or lossless captures, perdiod! ..and double-sheesh!

-vhelp 5436

[sanlyn]

The AG1980 is less prone to jitter than comparable JVC or Mitsubishi models, but it does happen.

I don't notice the Panasonic doing it any less than the JVC models.

This scenario is briefly discussed here: http://www.digitalFAQ.com/guides/video/capture-playback-hardware.htm
Scroll to the bottom of the page for sample images and text.

Sometimes I just couldn't use the player's onboard TBC to remedy this problem. Typically it wasn't the player's fault: the tape was physically damaged. But occasionally I was able to turn off the line-level TBC and do this:

With the player's TBC disabled, repack the tape to help level the way the tape is wound onto the cassette and to aid the tape's own flexibility at partially straightening itself. Do this by forwarding the tape all the way to the end, then rewind all the way back. You might have to do this 3 times or so, but once usually works.

Next, with the player's TBC still off, connect the player's output to a DVD recorder that has a built in line-level TBC that can be used as a pass-thru device. Don't record into the DVD recorder itself; with the player TBC off, you'll likely have to do some color correction, etc., in a computer anyway (or use a proc amp, but only after the video has passed thru the recorder). Feed the interim recorder's output to your final recording device. I don't record into that interim recorder itself because the tapes I've used with this method require more processing and because many of those tapes are copy protected. With the interim recorder's TBC, macrovision is usually removed at the pass-thru machine's output. I've also used this method to record copy-protected cable.

The recorders I've used for pass-thru TBC are the Toshiba RD-XS34/35, Toshiba D-KR2, -4, and -5, and the Panasonic DMR-ES20, -10, and -15 (Line 1 only for the Panasonics. The other inputs don't use TBC). The Toshibas were usually more capable.

This has worked for me about 75% of the time. That other 25% is just hopeless, period.

[orsetto]

The "jitter" or "judder" response when TBC is engaged is largely due to the underlying barely-functional nature of consumer VCR technology. Not in their wildest dreams did the inventors of helical-scan VTRs ever imagine the design would be scaled down to a tiny plastic box with tapes a quarter the width in a crummy mass-produced shell running so slowly (at EP) as to be barely moving at all. All these factors combine to make for an essentially shoddy recorded signal, targeted to take advantage of the "slow", analog, forgiving nature of CRT television displays. Consumer VHS, especially EP, was never envisioned to play on a digitally-controlled 46" flat panel LCD, or be dubbed to a digitizing encoder. That this works at all 85% of the time is nothing short of astonishing.

The other 15%, we wrestle with, and sometimes need to accept failure with. The "TBC" embedded in these VCRs is not a full-fledged TBC in the professional sense: it is a "head" TBC, tapping the signal straight off the spinning video heads and conditioning it to look smoother and more stable. In this design, any significant "bump" or split-second bad patch in the tape will overwhelm the TBCs ability to stabilize it, resulting in a "jitter" at that moment. This is exacerbated by the fact all built-in TBCs are locked together with digital noise filters: the Panasonic DNR is always on, even if the TBC is off, and the JVC/Mitsu design is all-or-nothing (TBC/DNR are both on or both off). At times the DNR works at cross-purposes to the TBC: some artifacts of color and luma noise shaping result in signal spikes that again outstrip the "speed" capabilities of the TBC to stabilize, showing as a jitter or judder.

No doubt much of this is connected with the "antiquated" TBC/DNR systems of these VCRs, the most recent design being last updated in the late 1980s (even the newer Mitsubishi and JVC DVHS models rely on relatively ancient TBC/DNR circuits). I'm sure if consumers were willing to pay $1995 for a totally new ground-up VCR designed for digital dubbing, these jitter artifacts would be completely eliminated. Short of that, the best (and only) workarounds are the ones outlined above by robjv1 and samlyn (excellent posts, guys - very helpful and detailed!) If you don't want to go to all that effort, the default option is to switch off the TBC and/or DNR and compromise: the dub will be noisier, but the synthetic jitter will be eliminated.

[paulopereira]

https://youtu.be/PXpCiunLRn0
I'm converting my VHS and S-VHS tapes to digital. I was using uniquely JVC HM-DR10000 and JVC HR-S9700 (PAL models) and Canopus (Grass Valley) ADVC-300. I was using only the videos TBC (line TBC) instead Canopus TBC: so, the Canopus was only doing the analogue to digital conversion. Today I tried to use my Panasonic AG-8700 full frame TBC (note: I don't use it as a player because most of home tapes do not play so good in this pro model). Well, I discover AG-8700 full frame TBC is the best I have: much better than JVC line TBC or Canopus TBC. Unfortunately I've one problem: sometimes scroll happens (attached video). I've tried the AG-8700 TBC settings but no solution. Do you think I could do some DIY? I've the service manuals but no serious technician skills. Also I'm using high end cables: DPA Black Slink silber cables with WBT (audio) and Nordost Optix Super S (s-video cable). Well, I need help...