Tiny Jitter Explaination question

[Cole]

Most of my video restorations are of vintage British television. The large amount of which are VHS tapes from late 80s up to the late 90s (mostly BBC).

I have just started to notice an odd jitter to all of my recent tapes. It isn't an obvious one, but a slight jitter which becomes quite visible if one looks closely at the screen and once you know it's there...

I have only noticed this on the last few tapes I have converted and I checked an older conversion and noticed it on this recording too.

I understand that VHS has all sorts of errors and movements, but can someone explain what the reason for this might be.

It isn't down to Macrovision, nor is this the VCR as the same thing occurs with both of my VCRs (JVC and Panasonic) and with any different settings too.

I am just curious as to what this tiny jitter may be; or is this going to be under the 'expecting too much/they all do that'' heading?

[Cole]

Actually, looking at the recent tapes that I have done have been of programmes from during the 70s and before; I think that this may be an issue with the quality of the original recording's age etc.

[gammer]

Can you try playing the tapes through another VCR?

If I have tapes that have jitter, I try playing it through an older Sharp 4 head VCR that I have and the jitter is gone.

[Cole]

It occurs in both my JVC and Panasonic. I think that I am experiencing this through what I can only describe as an unlucky batch i.e. several dodgy tapes one after the other.

[dphirschler]

I've seen this jitter before on a couple of tapes. On one tape the jjitter went away after I played the tape all the way through and captured on a second playing of the tape. Maybe even try ff/rw the tape once before capturing.

Lastly, if you are desparate, and have lots of free time, I wrote several functions in AviSynth for correcting this jitter. But it is not automagic. You must identify each frame and decide which field is jumping, which direction it jumps, and by how many pixels. Yes, it a PITA, but like I said, you gotta be desparate! Let me know if you want the functions I wrote. I will have to dig it up at home.


Darryl

[Cole]

Thanks Darryl; I would be a complet novice with AviSynth and the time that would take is just plain scary . It isn't that desparate thankfully, but what I will do is see what the quality is like when viewed on a television as I am seeing these jitters on an LCD monitor.

[dphirschler]

I forgot there is also a Virtual Dub filter called something like "Tweak" which also corrects the jitter. But it is very manual as well... and involves scripting (sort of).


Darryl

[Cole]

I dug out an old Amstrad (1991) VCR and tried a tape in that. Obviously much less detail than with the JVC or the Panasonic, but the jitter doesn't seem anywhere near as bad.

Seems is pays to have a collection of machines!

[gammer]

So I guess its a matter of weighing it out:
Do you sacrifice detail so there is no jitter?, or do you keep the detail but have it jittery?

[Cole]

Hmm... there is another trusty mid-90s Panasonic VCR (best I ever owned over the years) that I can get my hands on. It is currently in my Girlfriends house.

The detail on this was quite good, and in addition I have got a detailer now to help it along.

Ultimately I have to say though, it is stable over detail.

[vhelp]

Evening Cole,

I have only noticed this on the last few tapes I have converted and I
checked an older conversion and noticed it on this recording too.

I understand that VHS has all sorts of errors and movements, but can someone
explain what the reason for this might be.

What I think it is causing this, is the vcr(s) you are using. But..

I would suggest that you first analize your video playback performance
by first reviewing the tapes in each vcr and observe anything that
may be unsual.

If you conclude that your vcr(s) are playing them fine, then it is
a safe bet, that you not blame your vcr for the problem, and your next
analizing step would probably be, what capture device(s) did you
use in the capturing stage. Then, narrow it down to the MPEG encoding
stage and the methods/process/settings you used inside this phase.

Personally, I would *NEVER* blame the advc. This device is the
HOLY GRAIL of capture devices. I would presume it is something else
externally connected that may be influiencing (thanks to MV) and
resulting in your issues.

It is my honest opinion, that MV and Capture/TBC's do not always work out
well, regarding complete image recreation. I basically came and went
with this (specially TBC's) in my capture endeavors. I now rely 100%
on my ADVC-100 to capture clean and *stable* video, when the source
is VHS. And if I *really* want the most (anal) quality from VHS, I
will use my BTxxx cap cards for these (oh, but the noise.. that's an
whole aother issue) ahh.. compremises.

You could also throw in some specs as to your MPEG encoding process.
That might help to shed some light on narrowing down the actual
cause.

So, to recap:

** search your vcrs for performance issues (rule them out)
** next, see if your capture device(s) is at fault.. ie, advc; tbc; pro amp ..
** next, see if your MPEG encoding is at fault, ie, settings etc.
** or, consider trying your BTxxx card as a test.

Cheers,
-vhelp 3676

[Cole]

Hi vhelp.

The process that I have gone through all seem to indicate that the VCR/tapes are the thing at fault thus far...
Set up: JVC hr-s7965 vcr -> tbc-100 -> detailer -> advc50.
Certain tapes are having a minor jitter. I have changed settings on the JVC's menu, but this has made no difference.

If I add another item to the chain:
Sony VTX-D800U Digital Receiver -> JVC hr-s7965 vcr -> tbc-100 -> detailer - advc50.
The digital picture from the Sony is clear and jitter free, so this seems to rule out any issues with the TBC or detailer.

Another set up:
Panasonic NV-HV61 -> Sony RDR-HX510 DVD Recorder.
The minor jitters are still evident on the playback here.

As menitoned above, I then connected up an old (1990) Amstrad VCR8800 (which I only now use as a tape re-winder):
Amstrad VCR8800 -> tbc-100 -> detailer -> advc50.
The jitter seems to have gone, but the detail from this VCR was not as good.

I will do some further investigation with this when I get my old trusty (mid 90s) Panasonic NV-HD90 back, as I do wonder if the older VCRs were a bit more reliable than newer ones.

I am not ruling out that I have had a succession of bad tapes and this may be just an excercise in finding the best set up to deal with them.

[Cole]

I am not ruling out that I have had a succession of bad tapes and this may be just an excercise in finding the best set up to deal with them.

This does in fact appear to be the case; I am now capturing a tape with the JVC which is playing perfectly.

BTW; the jitter was evident at the capture stage and the MPEG side of things did not come into this.