|
Post by richardwoods on Feb 27, 2021 18:18:38 GMT
I was always a bit of a geek so I wired in a din socket into the volume control of my 405 line Murphy TV, braving the live chassis! Got some good results too recording at 3 3/4ips on to a Grundig TK14 2 track reel to reel. Never taped Dr Who, as far as I know all I’ve got left is a recording of the soundtrack of one of the Pythons (nothing special, it’s already been checked) & the soundtrack of the film the Andromeda Strain. My old Hitachi 21" CRT actually had a dedicated din recording socket mounted on the front of the set next to a jack headphone output. In the old days of audio taping this would have been a wonderful thing, but this set was circa 1982 - well into the VCR age. Mine was a 1960 Murphy 405 line set, a reclaimed scrap TV from Radio Rentals, we are talking about mid 1970’s. Good set, even had a built in FM radio! Was gutted when the oil filled line output transformer failed, a death sentence on a TV back then.
|
|
|
Post by peterconvery on Mar 5, 2021 21:28:58 GMT
So, before I posted something rash, I wanted to make sure I was talking sense and went off to find some more info. lets start with a process of elimination -
Its long been established that there is zero per cent chance of any video signal being recovered from the audio tape recordings (see 3rd post from Clive Shaw and continuing conversation) it simply doesn't have the bandwidth, frequency and speed of the tape to record anything. which was around 50 -60 MHZ
So I looked at it from a different angle, what about TV buzz or interference being on a separate track of the tapes -could anything be there?
Which led me to the moon recordings - how did they transmit a picture signal back to earth?
Well, they used s-band transmissions sent on low band frequency using a device called a Vidicon. Vidicon is smaller version of a cathode ray tube which converts light signals into electronic beams and would then send them by MW frequencies. Back on Earth they would then pick up these transmissions and the using a scan convertor they would then convert the image into a moving picture. As it was low band it would only convert at approx 10frames per second(which would give something watchable but could cause ghosting if an astronaut moved quickly). Low band frequencies transmitted from 500KHZ with a progressive scan giving 10 fps at 320lines or 0.625 fps at 1280 lines using a ratio of 4:3. TV stations then would convert this into a tv signal and relay it across the world. TV's in the 60's used cathode ray tubes and MW to send transmissions over the airwaves.
Graham Strong recorded between 50 and 60 MHZ at a tape speed of 2.5 inches per second. It now doesn't matter what speed it was taped at as we're not looking for video signal, or the size of the bandwidth as if there is low bandwidth recorded it can be converted and adjusted accordingly coming out the other side. What we're looking for is the direct line signals and any code from the tv that might have been picked up on tape. Why direct line? Well back in the 80's during my mis-spent youth of plonking of school....I mean during the summer holidays, we would play computer games like manic miner, jet set willy and football manager, from time to time we would try some other games like jet pac and atic atac but we always went back to ye old faithfuls....one day we decided to swap games and try and record them for each other, so he told me to bring my tape recorder round, which i did, however i left my jack plugs behind thinking he already had some. now his jack plugs were already in use for his computer, tape recorder and tv, so we put the tape recorders as close together as possible and took out the sound jack to get the audio of it. We managed to load the game up on tv, and we recorded R2-D2 getting scrambled in a microwave onto the other the tape, however when we linked that tape up to the computer......nothing happened, plainly we didn't use the jack plug and get a direct line recording (we were only 10 years old) and ended up with what we now know as a 'mic' recording. Same with those old 60's audio reel to reel tapes. It needs the direct line to get a chance of a signal.
So whats on there? Well looking at the DMP page on the restoration teams webpage Mark Ayres talks about easily removing background hum and hiss from the tapes that were 'mic recordings'. My heart skipped a beat when I read that some of the Graham Strong recordings suffered from some interference.....! ok....what was that? Could it be the intermodulation distortion that Sue was talking about? if so then thats pretty useless...you wouldn't get a clear picture, only brightness and darkness, but what if it was 'something' else?
So now NOT needing the bandwidth or speed of the tape and hoping that there is some code on one of the tracks on the audio tapes, can it be converted into moving frames? Using todays modern computer equipment - yes - in theory we could have a possibility of up to 76.5 episodes recovered using this technique - (Some episodes have 2 bites of the cherry, see my previous post to see which ones) The signals can be scan converted and by changing your picture size you might be able to recover some low definition moving pictures - at best 10fps, or 4-6 fps, or 1 fps or 1 frame every 2 seconds. Worst case - nothing at all, but what have we got to loose?
Now i'm sure someone more technical gifted or perhaps someone from the RT or Mark Ayres himself will come along and shoot my theories down and pick out all the flaws in my ramblings, but I live in hope...
Heres for the best... Peter
|
|
|
Post by Richard Bignell on Mar 5, 2021 22:04:31 GMT
The "interference" being referred to would be the fact that Graham's recordings sometimes picked up stray radio signals from France. He lived in Exeter at the time and atmospheric conditions could lead to stray signals bleeding through onto the recordings.
|
|
|
Post by peterconvery on Mar 5, 2021 22:15:08 GMT
The "interference" being referred to would be the fact that Graham's recordings sometimes picked up stray radio signals from France. He lived in Exeter at the time and atmospheric conditions could lead to stray signals bleeding through onto the recordings. Did France ever show Dr Who? :')
|
|
|
Post by richardwoods on Mar 6, 2021 11:09:09 GMT
The "interference" being referred to would be the fact that Graham's recordings sometimes picked up stray radio signals from France. He lived in Exeter at the time and atmospheric conditions could lead to stray signals bleeding through onto the recordings. Ah, Band 1 in the summer & the joys of co channel interference!
|
|
|
Post by richardwoods on Mar 6, 2021 11:10:24 GMT
Don’t forget 405 line stabiliser whistle bleed over on to microphone recordings too!
|
|
|
Post by John Wall on Mar 6, 2021 16:56:43 GMT
The impossible we can do given time, miracles take a little longer.
Any sufficiently advanced technology is indistinguishable from magic.
|
|
|
Post by richardwoods on Mar 6, 2021 17:57:43 GMT
The other thing to remember is that the video signal & audio signal were transmitted on different frequencies. Now it was perfectly possible to miss-tune a 405 TV set so that the video signal could be “heard” and then recorded on an audio tape, however why would someone intentionally do that and waste a spool of tape recording jarring noise, and secondly with the audio bandwidth restrictions in addition to recording at a maximum of say 3 3/4 inches per second, there would almost certainly be nothing salvageable. Just look at the problems engineers have trying to recover genuine reel to reel video recordings and these were made on proper equipment
|
|
|
Post by peterconvery on Mar 6, 2021 18:05:06 GMT
The other thing to remember is that the video signal & audio signal were transmitted on different frequencies. Now it was perfectly possible to miss-tune a 405 TV set so that the video signal could be “heard” and then recorded on an audio tape, however why would someone intentionally do that and waste a spool of tape recording jarring noise, and secondly with the audio bandwidth restrictions in addition to recording at a maximum of say 3 3/4 inches per second, there would almost certainly be nothing salvageable. Just look at the problems engineers have trying to recover genuine reel to reel video recordings and these were made on proper equipment Thats it....what if it was recorded there by mistake and is hidden on one of the tracks....thats my point. Can it be separated and recovered? If its there in the 1st place! Nobody's ever confirmed either way, thats why I'm asking
|
|
|
Post by Richard Bignell on Mar 6, 2021 19:49:06 GMT
It wouldn't be on "one of the tracks" as the recordists didn't use multiple tracks. They recorded on just the one.
|
|
|
Post by peterconvery on Mar 6, 2021 20:19:03 GMT
It wouldn't be on "one of the tracks" as the recordists didn't use multiple tracks. They recorded on just the one. Aha, so they used just one line? Thanks Richard
|
|
|
Post by Richard Bignell on Mar 6, 2021 20:22:33 GMT
Tape was expensive, so the episodes were recorded on a single track at slow speed. That way, a large number of episodes (32 in total) could be recorded onto a single reel using all four tracks.
|
|
|
Post by richardwoods on Mar 6, 2021 22:55:10 GMT
The only way part of the video signal would have been recorded as audio is if the TV had been deliberately miss tuned to align the video frequency with the audio on the TV. That would never happen as there would be no sound track on the recording just noise. Reel to reel recorders back then were single track mono and would only record one track at a time.
|
|
Richard Develyn
Member
The Cloister Bell is ringing Bong! Bong! The Doctor needs to save us from Climate Change and WW3!
Posts: 588
|
Post by Richard Develyn on Mar 7, 2021 9:18:27 GMT
A computer might be able to turn animation into live action which looks "passably" real.
Someone would have to construct the animation first, of course.
Richard
(P.S. Sorry - this was in answer to a comment made a little way back, I got caught out by the forum's web site!)
|
|
|
Post by peterconvery on Mar 7, 2021 11:27:31 GMT
Tape was expensive, so the episodes were recorded on a single track at slow speed. That way, a large number of episodes (32 in total) could be recorded onto a single reel using all four tracks. Richard, did all the people who direct line recorded tape the same way? Did they all tape using the 4 tracks up?
|
|