OT:copying vhs tapes for dvd

mel58i wrote on 10/29/2004, 3:36 PM
I am asked occasionally to copy an old vhs tape to dvd, and not having a dvd recorder have to resort to getting the data into the pc and doing a mpeg conversion etc.
The fact that most tapes being old they have a few crinkes and the like, which is really giving me a hell of a time in getting them in to the pc without having dropped frames and sometimes total freeze-up for a couple of seconds.
I have tried using my XM2 as a A to D converter to firewire and also going into my DC10+ capture card with the (crap) Pin stud s/w. I find myself editing out bad frames and the like, but the results are rather patchy when I find that any background music is disjointed due to the edits, and I suffer A/V sync problems when cutting out repeated frames due to "drops".
I have concluded that tapes must be in pristine condition to aviod these problems!
Wonder if I can have any input from anyone who has been in the same situation.
I know that a TBC would makes things better in reconstituting the sync - but would this be a cure or just an improvement?

Mel.

Comments

farss wrote on 10/29/2004, 3:48 PM
Once you've lost the oxide on the tape nothing is going to help, it's just gone.
TBCs certainly help, nothing drives the following A->D conversion nuts like losing sync so yes it's big help with problem tapes.
There is technology called dropout compensation that's even better, it has to work from the RF signal coming off the heads and it attempts to patch missing bits from the previous line of video. I haven't heard of this being used on VHS though, it's standard fare for BetaSP and UMatic VCRs.
Failing that, S&W make some boxes that do true digital magic but for a BIG price, I suspect there's nothing on VHS to justify the asking price. However you can send material to a bureau service if your clients have very deep pockets.
If you're prepared to spend the time doing things by hand here's a few tips:
Don't cut frames out, copy adjacent frames or merge two adjacent frames to avoid the stutter.
Motion Blur can do wonders if used sparingly, I've fixed many problems using it, probably by using that in conjuction with having two tracks and using the CC you could do even more.
VD and AVISynth have many NR tools as well.
If you want a box to do some of the work for you, the ADVC-300 works very well, both TBC and temporal NR.
When you go to DVD noise is a BIG problem, anything you can do to get rid of it will help.
Bob.
johnmeyer wrote on 10/29/2004, 4:53 PM
I agree with everything farss wrote. My only addition is that in my experience it is uncommon to have single bad frames with analog tape captures. Usually, if it is a lost sync issue, you lose a lot of frames. If you are getting just one bad frame at a time, that sounds more like a capture issue. Can you capture without dropped frames when the tape is really clean, or when you capture a digital source? Also, you deck probably has automatic tracking. Usually this works just fine, but you might want to experiment with the manual tracking controls (often the channel up/down buttons adjust tracking during playback). See if you can get a better picture or better sync.
mel58i wrote on 10/30/2004, 1:52 AM
Yes, I do have a bunch of bad frames when I get to a bad point on the tape. I agree that single drops is usually a capture problem.
I think I prefer capturing via the XM2 (GL2) A to D (firewire) since the sound is captured with picture so, if I get bad tape, there is no transfer so effectively don't get the A/V sync problems. When capturing with the MJPEG card the sound goes via the sound card and this continues to be captured when the vid is losing frames - hence the A/V sync problem using this method.
Since dvd's are a fairly recent technology, folk are digging out their old wedding vids etc to have put on disc for preseving, but the fact that the vid is well used and old makes the job of transferring even more difficult.
If I got sufficient transferring to do then I would invest in a TBC, but again, will the usage justify the cost?

Mel.
johnmeyer wrote on 10/30/2004, 11:49 AM
If I got sufficient transferring to do then I would invest in a TBC, but again, will the usage justify the cost?

Someone who has actually used a "full-on" TBC will have to comment. I have only used VCRs that have a TBC "built-in," but it turns out these time-base-correctors aren't really the same thing.

My understanding of the theory of the TBC makes me believe that they would not stop the tape from losing sync, because the correction is applied after the tape signal has left the VCR, and therefore if the VCR's servo is actually hunting due to bad signal, the video will already be screwed up beyond repair. The main reason for the TBC when transferring analog video to another analog deck is to eliminate the phase shift from subtle timing errors so that you don't get "flagging" at the top of the picture and other artifacts that result from the timing signals being off by a few microseconds. Loss of sync is not a microsecond thing, and the signal is REALLY screwed up when you loose sync. Therefore, I wouldn't expect a TBC to help.

The original reason for TBC (and synchronizers) was to "line up" live video signals from two different sources so you could switch between them without having any artifacts.

I have always believed -- perhaps incorrectly -- that if you are not copying directly from one VCR to another, that a TBC wouldn't help. My reasoning is that the digitizing process does not involve any of the various snyc signals because the video is now just ones and zeros. Thus, if you digitize, and then go back out to VHS, then the sync signals will be re-created completely from scratch by the D/A in your 1394 device (e.g., your camcorder) when you print back out to tape. Since I have never seen any "flagging" in any analog capture -- even from tapes that exhibit flagging when played on the monitor -- I have questioned whether a TBC would help. I'd sure like to see a ten second AVI from the same footage captured with and without a TBC to see for myself if there are any differences.

Having said that, if someone else who actually owns a big-time TBC chimes in and tells you otherwise, based on experience, believe that person, not me.

BTW, you might find this article useful:

Time Base Correctors
farss wrote on 10/30/2004, 3:10 PM
John,
a TBC will certainly help when digitising an analogue source, particulalry one from VHS. With a TBC before the A/D converter it's always getting a stable frame. Without the TBC the A/D gets lost when things go wrong on the analogue side. So the A/D can end up making things look worse than they were while it tries to get itself back in sync.
I've never tried to capture VHS without a TBC so I cannot truly say just how much difference it makes. I started out using my humble D8 camera not even realising its advantages as they have a TBC and DNR. Since then I'm using an ADVC-300 and clients have regularly said their VHS transfered to VHS looks better than their tapes ever did. I'd take that comment with a grain of salt of course.
I'm no wizard on the intricacies of analogue video but I do know VHS is a dog of a system. Try feeding the output from a VHS deck into a DVW 500 and it laughs at you. I'm told the problem is VHS is a non heterodyne system, I think that means the color burst isn't locked to anything but others might be able to fill us in on that one. Either wa, whatever it means it does mean the output of a VHS deck will not go into a lot of the pro analogue gear anyway.
Getting back to what can be done, well my workflow is Super VHS deck to ADVC-300 via S-Video, just to get as much bandwidth as possible and then into VidCap.
As to whether you can justify the cost of this in a commercial sense, hard to say, most of the STB DVD recorders now have TBCs on their composite inputs so Joe Average can get close to the best you could offer anyway. Mostly the public are of the "if its got color and it moves its video" school anyway. With commercial services offering VHS to DVD at $10 or less per hour, you do the sums!
Bob.
mel58i wrote on 10/30/2004, 3:15 PM
Many thanks to Bob and John for your comments.
I can now see that a TBC for my application would be quite useless. Yes I agree that slight changes in sync position could cause the bent telegraph pole effect - a similar effect existed on old tv's which had to have a special channel dedicated to vcr as the 'flywheel sync circuit' was too sluggish to follow minute changes in sync timing. A TBC for this purpose (and copying to vcr) would clean up the timing.
If the tape is bad in the fact that picture signal suffers (and sync as well) then no amount of TBC would give any improvement.
Many years ago you used to see vhs vcr's advertised with 'drop out compensation' which would at the head level replace a bad line with the last good one. Whether this is still done or not I don't know. Manufacturers don't seem to give a full specification of 'domestic vcr's' - again why should they - it doesn't mean anything to the average user!
So it does look as though TBC's are out for me - just a matter of making sure that my machine is in tip top condition - and don't accept any tapes that have sign of more than a minute amount of overusage (difficult when it's a 10 year old wedding vid that has done the rounds!
Digitising maybe a good thing but it can't think like a human brain and make allowances for less than perfect material!


Mel.

P.S. Just seen your post Bob as I was typing mine - all this throws a spanner in the works! Anyone want to complete the spanner toolbox?
mel58i wrote on 10/30/2004, 3:33 PM
Bob,
Get what you say, that a TBC before the digitiser will at least give sync signals while the vcr is sorting itself out. Would the final result not then be what is seen on a monitor before the TBC (from the vcr)? Would be nice if the tape was at least copied into the pc "worts and all" if it could not be made perfect. "As seen" must be better than a screwed up digitise with dropped frames!

Mel.
farss wrote on 10/30/2004, 8:55 PM
This is where things get confusing, monitors and TVs are for more tolerant of sync problems than A->D converters, they have to be to cope with horrors like Macrovision. Further down the track of course the mpeg-2 encoder is trying its best to do temporal compression so having a whole frame shift of having it full of noise doesn't help at all.
Dropout compensation and TBC would be great, we've got a unit that works with our Umatic VCR but it's fed the RF signal from the heads, that way it knows something is missing off the tape. I'm not aware of any VHS VCR available with this, Panasonic maybe stull have one, I know they still made some pretty expensive Super VHS VCRs that may have this that'd also do the trick for VHS, I didn't look very far into them as they were expensive and NTSC only.
If you don't want to spend a lot of money I'd get a D8 camera second hand, I'd imagine you could pick up one that's got a dead transport / broken lens pretty cheap on eBay. DV cameras don't have TBCs or DNR so they'e got nothing to offer.
I hate making recommendations!
I have the ADVC-300, we've used it in place of kit costing heaps more for digitizing from BetaSP as the other gear didn't have a TBC. It's not that expensive, if you just want to do the odd tape of your own then yes it's quite a few dollars, if you charge for what you do as I do then I figure the customer deserves the best shot I can give it. If they want it done cheaper there's always the kid down the road.
One big plus for the 300 is it'll handle both NTSC and PAL, so I've done a bit of work capturing NTSC VHS, converting to PAL in Vegas and then PTT to DVCAM. This material goes to air and / or onto commercial DVDs as trailers.
One other thing not mentioned before, it can help to run the tape more than once if you're really keen, capture it doth times. Apart from the noise reduction trick, sometimes you get a better signal on one pass than the other. You should also spool the tapes first to even out the tension and if the tape is in really bad shape your heads may need more cleaning than normal.
Also if you can find an older VHS deck that doesn't do LP you may get better results, these have a wider head which may help.
Bob.