Even thou my Panasonic NV-Hs860 VCR has a TBC I found that it dealt well with horizontal jitter but would not stop the vertical roll which occured when I tested some of my worst VHS tapes.
So after searching for external TBC's I discovered that some (warning not all!) video mixers have full TBC's. So anyway I bought a 'Video Tech VMX410' (also sold as Vivanco) details on likes below:
some more on mixer
Anyway I've had a play and all seems to work. To fully test the TBC I used a really bad bit on a tape which on usually just turns into a continous rolling of vertical white lines for about 5 seconds. The HS860 VCR TBC can't stop it but the VMX410 does stop the rolling but although the image is firm lines still travel down quite badly.
I've read that high spec TBC's can remove the thin white line errors that occur (dropouts) by using a stored previous line to fill-in the gap. Apparantly these errors are caused by physical wear on the tapes oxide layer. Unfortunatly I may have made this part of the tape worse by cleaning it a year or two ago. I used head cleaning fluid and cotton buds to gently remove some mould that was on the tape surface I prosumed this was causing the rolling of the picture. Now I know about timebase errors and think possibly a new timecode from TBC may have been enough. Its hard to say whether the mould or the cleaning did the damage.
I'd be interested on anyone's opinion on these problems. Basically I want to know if the VMX410 is doing its job right, I've checked all the info and it has a full frame TBC but at some point you reach a level dictated by cost/time where you have done as much as you can to improve an old tapes quality and you just have to copy and bin it.
Has that time come?
a full list of articles on the site for reference to anyone interested :-
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If some or all of the Vertical Interval is missing during playback, then any TBC may have difficulty. Have you tried turning off the VCR TBC and using just the TBC in the Mixer?
A different VCR may actually help more than a different TBC because it may be able to recover more of the Vertical Interval.
Dropout compensation on some TBCs typically requires a Tape RF signal from the VCR to detect the loss of playback signal (and therefore a dropout).Life is better when you focus on the signals instead of the noise.
Thanks for the reply davideck,
If some or all of the Vertical Interval is missing during playback
I did switch of the VCR TBC as -I think you said on a post to someone else- the first TBC does the correction only.
I found another good test specimen over the weekend. This had a complete rolling/white fuzzy/blank screen part for a few seconds so I used this bit. My Sony SLV-E820 had complete failure, while the Panasonic HS860 failed less, with the internal TBC not providing any help.
(I will test on JVC HR-S5595, samsung VCR just to be certain Davideck)
I tested the alternative Sync function on the VMX410 TBC/Mixer which has 3 different sync options for roll (and another set for colour flash, not needed yet). One of the sync settings was able to keep a constant image (passing through the DVDR which grey screens at image failure).
Unfortunatly there are still fuzzy white bars that travel down the image.
When I checked the tape's condition I did find a small cut at the side of the tape at this point and surface mould areas. This looks like sort of flowery shaped patterns that look matte compared to the usual shiny brown of the tape. I cleaned this of using a cotton bud dampened with water and dried straight away with cotton wool. This has been caused by not leaving the tape fully rewound to the clear tape ends. That leaves the area on the tape exposed to damp and mould growth and always seems to be at the start of a program!
After cleaning the tape the picture improved abit but I think the mould may damage the tape surface and actual remove some image signal even after the tape appears shiny again.
I'd be interested on anyone thoughts on this as there's a few things going on and I'm trying to put my finger on the problem. Only with the chance to use a professional grade TBC unit could I set my quality threshold, until then your left wondering if it could be improved some way.
Pass-though Colour and Cables
One last thing ; I've noticed that the pass-though picture loses some colour (the review linked above says there is no loss). The best test is on close up of faces which shows a less healthy colour due to red loss. I can increase saturation but can't increase red alone. I've used top quality gold/double screened composite video cables in/out. I only have 1 basic s-video cable now going in with the comp. going out. Is it worth the investment in 2 good s-video for in/out is that likely to hold colour better. I need to know it's worth having an extra TBC if it losses 'reds'. It won't be a hardware fault as its too minor but I don't want any loss than I can help. If you've maaged to read this far down Davideck I believe you said you used a datavideo tbc1000 have you noticed any colour loss with different cables.
Originally Posted by StuR
Originally Posted by StuRLife is better when you focus on the signals instead of the noise.
Once again thanks for advise davideck,
I know it converts S-video to comp in any combonation of in/out, but your right that requires some convertion which is going to be a likely cause. I'll go for good quality if I can get for cheap just in case, I was thinking the shorter the cable the better?
I've read the red is video's (tape) most troublesome colour usually too much, then it goes! swine.
Back to - dropout's and rolling
You've suggested previous (davideck) that the two most important factors in a good recording are the tape condition and the VCR playing it. This is the message I got from reading another hot debate about TBC's. So I tested the two poor tapes on all my VCR's.
Samsung SV-640B ..... rolling at bad bits
JVC HR-S5595 ........ total grey sceen on worst tape, rolling on other
Sony SLV-E820 ....... some rolling
Panasonic NV-SJ210 .. lots of rolling
Panasonic NV-HS860 .. rolling usually gone
(no TBC used at all on any)
I actually found that the HS860 was reducing the rolling (usually stopping, but on repeated play sometimes small rolls). This must be due to a better mechanism. I had hoped this would be the case after buying the thing but hadn't tested it fully. Davideck you did advise to begin with a better VCR to begin with and you're quite right.
I used to use two panasonic NV-SJ210 to copy tapes and they seemed like good players but I remember cleaning some mouldy tapes in the past and still having the rolling, which made me think I'd rubbed off something on the tape. It looks like that its the poor quality of the player.
And finally I did check the HS860 and the VMX410 (ext.TBC on only). With the sync lock adjusted it always seems to stop rolling, so looks a safer option for recording problem tapes.
But it is only a small improvement really 'an icing on the cake', the main improvement has been in a better VCR, and cleaning off the surface mould at these bad areas.
And as far as the white line dropouts they looked to remained constant on all VCR's I used. I think mould has travelled between the two plastic laminates of the tape and damaged the recording medium. Even when cleaned you can see small patches which resemble frost patterns on a window. I think these could only be removed by a TBC with dropout repair or maybe via computer program, but I don't have the money for the first option and using the computer would add too much hassle.
I hope this helps some one else with these problems.
I'm just adding one last link, I've been following LordSmurf's links
this is a very handy restoration basics list, which I wish I'd found previous, so hope it short circuits the search for someone else.