a little part of drwho 60hz video signal sync

[harry]

having an understanding of video and audio part of drwho from the 60's could still remain on the audio recordings. just the sync signal i don't think the video ,thats the brighness and darkness would of snunk past the tv filters and audio recording speed the
video would be very washed out if every thing was right to even record part of the 6mhz signal .
but rcording a small amount of the band that audio tape can record believe it or not you would be able to see some thing if just shadows .
i do recall the old valve tvs you could hear the hum on the audio so i know the 60hz sync would make it to tape and perhaps the horizonal 15725 hz ,i think it is from memory horizontal sync freq.
i havn't tried it yet but i am pretty sure with the electronics pll ics you could detect them even if they are below our hearing and weak on the tape ....
Trouble with the video brigtness if it did make it to tape
both audio and video signals are amplitude modulated meaning they'd muck each other up trying to decode them ...but never know these days with computers and removing one thing from another .Just been thinking about all this and no one has thought about it might lead to something else .harry

[williamM]

this was something I considered a couple of years ago but I decided that the tape speed would be too low to record enough of the picture signal, however, I wasn't sure and few people were able to help me, but what you say does sound interesting, do you think it's possible, I hope it is, do you have any more info on this?

[Clive Shaw]

Nope, audio tape has not got the frequency range to record anything of interest in regards to the video signal.

Recovering any video signal from audio tape would therefore be impossible.

[willamM]

well that's what I thought
tape would be about 20-20KHz
and tv would be about 20-200 MHz
so only about 1/10000th of the info would be on the audio and that would be a combination or smear of noise rather than clear components, but perhaps there is a mathematical process to decode this?

[williamM]

also I should add that since you have knowlege of video signals then my views count for less, it does sound like something may be recoverable, what would need to be done to reconstruct the signal do you think?

[Clive Shaw]

williamM said:

also I should add that since you have knowlege of video signals then my views count for less, it does sound like something may be recoverable, what would need to be done to reconstruct the signal do you think?

Nope, nothing would be recoverable, if the information is not there, it is not there. The only thing you will hear is the whistle of the flyback. The PAL colour carrier is at 4.43Mhz and I think the upper vision frequency of 405 lines is around 3Mhz.

This is well outside the range of a domestic audio recorder which has an upper limit as you say of around 20Khz.

[Jeff Stone]

Still, you gotta give WilliamM a Zarbi Badge for a fascinating idea. I had never considered that before; and though it's clearly not possible to recover any watchable video signal from an audio recording, the concept itself is an inspired piece of thought experimentation. Kudos

[Richard Bignell]

cliveuk said:

Nope, nothing would be recoverable, if the information is not there, it is not there. The only thing you will hear is the whistle of the flyback. The PAL colour carrier is at 4.43Mhz and I think the upper vision frequency of 405 lines is around 3Mhz.

This is well outside the range of a domestic audio recorder which has an upper limit as you say of around 20Khz.

Indeed! One only has to remember the Fisher Price PXL-2000 video camera that was marketed for children many years ago that did indeed record its images onto standard high-quality audio cassette. However, the tape had to be run through the system *very* quickly in order to record its 100-line 15fps b/w 1/4-screen image at all - a 90-minute tape would only yield around 6 minutes worth of very fuzzy material.

The chance of a proper full-strength television signal being captured on a standard audio recording is zero - although I had the same thought in the late 70s when I was audio taping the programme for posterity!

Richard

[Wright Blan]

It might be interesting to try just as an expiriment to see if anything showed up. Weirder things than this have turned up.

[Clive Shaw]

Well to be honest that would be very weird

But no, although it sounds logical, the physics of it would make it unachievable. If you have seen those pictures of the early BBC 'Vera' video recorder which ran at an almighty speed to record and produce (pretty ropey) pictures, it was only Ampex and its eliptical recording head which allowed video to be recorded on magnetic tape at a decent (and safe) tape speed.

Add to this that all of the DW audio recordings were either just microphones in front of the speaker or wired into the audio stage of the TV (never going anywhere near the video signal) then there would be absolutely nothing of use recoverable from the tape.

But of course I would love to be proved wrong on this and would quite happily nominate anyone who got result from this for a Nobel Prize in "Advancement of Electronics Knowledge" whilst simultaneously eating my hat.

[williamM]

it would need a great deal of manipulation to get anything useable but who knows, perhaps some process will turn up in the future, I'm sure there are processes to extract information, overalaying as many recordings of the same thing as possible would give more information to work on but even then it would take 50-100 to get enough inforation. This definitly needs some sort of interpolation software.

[Clive Shaw]

williamM said:

it would need a great deal of manipulation to get anything useable but who knows, perhaps some process will turn up in the future, I'm sure there are processes to extract information, overalaying as many recordings of the same thing as possible would give more information to work on but even then it would take 50-100 to get enough inforation. This definitly needs some sort of interpolation software.

Nope, that wouldn't work. If there is nothing on the tape to begin with, then you could have a billion tapes but still nothing (100 x 0 = 0)

[williamM]

but 100/0=infinity

[Jeff Stone]

Infinity is by definition impossible to achieve. It is as hard to attain as it is to find an episode of Charmed without a single cleavage shot in it.

I still maintain that the only real way to recreate the episodes is to wait for computers to get a bit more advanced (only a wee bit, mind you) and then use the telesnaps as a guide for making full-length photorealistic CG animated remakes. Despite what others have said, there is aboslutely no technical reason why this cannot be done. Cost is the only problem of importance, and improvements in computer processing power will reduce this soon enough.
Who knows, ten years from now we may even be able to get a Reverse Standards Conversion transfer of a Pertwee episode that isn't washed-out and juddery. ;D

[Clive Shaw]

It's is not about how much power a computer has got, it is about how it processes information. You need to give it raw data to compute against.

What you are asking the computer to do is to guess what live action is happening between the Telesnap guides. Please explain how a computer will do this ? You are asking for a computer that thinks, computers do not "think" they process based on input.

You claim there is no technical reason why this cannot be done. If so then please explain to us how you envisage this is technically possible ?

What you are claiming is impossible and will remain so until someone (you?) devises the machine that could possibly do this. You are still waiting 30+ years for it (neural network based nano technology is the best starting block)