A different type of photography - S-VHS corruption!

10-10-20

I'm hoping that I'm not too far off the mark here but I figure that somebody here can give me some pointers.
I'm converting a load of old S-VHS tapes to MPEG-4 and I've come across a whole bunch (all high quality TDK tapes) which all have this type of corruption. All of the tapes are home movies, very sentimental due to a recent family loss.



Typically the whole tape is like this, but there is one single tape where three recordings have been made to it, but the second recording is perfect and the rest are corrupt.

For this reason, I'm not suspecting the TDK tapes. I'm suspecting that it's a problem with the original VHS recorder. I haven't to this point in time tested it on another VHS player (as I need to clean them first).

So, who can offer opinions on the cause of the corruption?

telecinesk

Hi,
forgive the obvious, is the machine your playing off S-VHS itself, reason is the luminance seems way high and i recall that kind of error when wrong vhs machine used.
alternative is the sync pulses are all over the place and there is tearing so that leads to head wear.
Also the video level (RF) looks v high, can you pull down the video input to the card. VHS tapes tend to survive with age,so it looks more machine/video level problems. Blacks look grey, so im with this opinion. Find another SVHS recorder and confirm?
Worst case would be wrong tape in standard vhs machine and simply the bias is wrong and the actual recording is ruined as is. dunno really unless I saw it directly. Ask someone in the business maby who does video transfer for a living. Best of luck, hope it helped a bit.

10-10-20

Hi telecinesk, yes the player is S-VHS and is a good quality 6-head Sony model. The image was taken in 1989 or 1990 with an 'over-the-shoulder' camera and the general quality isn't fantastic on any tape captured by it. What's more, I suspect that some of these are second or third generation copies of the original media, so that accounts for some of the problems.

The luminance goes mad when a tape with this defect is played - but other tapes come out well and I already have ~100 hours of tapes recorded at a good quality, just these 10 tapes are behaving as you see here. The image I have included is one of the better ones - the rest show very little picture, just lines like the bottom third of this image.

I read about a plugin for some encoders (I'm using mencoder) which uses a 'majority vote' method to process the images from three recordings of the same tape to eliminate the lines. Ever heard of it?

I have ~250 tapes in all to process, so I want to understand these issues early on so that I know how to recover them. Thanks for any pointers!

telecinesk

Hi,

thanks for info. Ok, looks more like orig recording from the camera is out of spec if its coming off the tape like this in the correct machine.
Or its multigeneration leading onto the tearing and very ropy syncs.
If you had access to an oscilloscope you could look at the video waveform and see whats coming off the machine with the tapes.
Granted its going mad technical but thats how I would start. No plugin will correct this beyond pulling the whole luminance down to grey.

Id get the analogue signal analysed first. have you access to anyone in the trade with some experience in the above. I wonder if you got your hands on a timebase corrector and tweak the luminance you may pull more signal out. One thing is clear,the syncs need to be replaced for anything to lock onto the output.

If your svhs machine is playing nicely then its the origional 10 tapes you have.

Thats about all I can suggest. Best of luck.

The Doktor

Jaysus lads, before you get the scope out the first thing to do with any dodgy picture on a vhs machine is to clean the heads. Dirty heads can effect different tapes in different ways, or not at all. Putting a scope on is going to tell you nothing at all.
Now i dont mean putting one of those cleaning tapes in (id say of the hundreds of video heads that ive needed to replace most were actually damaged by cleaning tapes).
Open the machine and clean the heads with a business card and some alcohol. And make sure you clean the audio head and the erase head too. And after you cleaned it... clean it again.

chisel

Clean the heads, and the other thing I recently learned is that apparently VHS tapes need to be wound every year of storage to keep them OK. So I had a similar situation to you, only worse in fact, and managed to get over the problem by FF and REW them a few times before repeat playback with cleaned heads.


Tapes do go off......

10-10-20

Hi guys,
I tried an old VHS deck and I had the same corruption. The heads were clean in the Sony deck, so it's not that.
Some of the tapes are copies alright, and I found some or the originals, but I still have others which I don't have copies of.
I have ~220hrs of VHS converted over to MPEG4 now, so I'll come back to these tapes later on.