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Post by Sue Butcher on Jan 6, 2019 11:31:35 GMT
It would be nice if someone could explain simply how they're getting a picture in 625, instead of telling us how poor the results are.
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Post by Peter Lynch on Jan 6, 2019 12:12:50 GMT
It would be nice if someone could explain simply how they're getting a picture in 625, instead of telling us how poor the results are. Hi Sue I hazarded a guess in my previous post as to the ‘technique’ employed and the resultant quality seems poor . It’s my opinion and nothing more
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Post by John Marshall on Jan 6, 2019 21:58:50 GMT
It would be nice if someone could explain simply how they're getting a picture in 625, instead of telling us how poor the results are. Hi Sue I hazarded a guess in my previous post as to the ‘technique’ employed and the resultant quality seems poor . It’s my opinion and nothing more I don't know how that is your "opinion" when its a pretty clear and objective fact, don't sell your appraisal short. When I copy VHS over to the computer its fairly simple, software that is able to read the incoming feed displays EXACTLY what its playing and a digital copy is made. How is this not the case with this system? A problem of software? Its certainly not the machine being used. If it can read 405line tape it can display it properly if it has something to convert that feed into a continuous video image. Are we trying to reconvert to a tape source and thats the issue? Why? Very confused here. We can take pictures of film sound and reconvert it to digital sound but we can't get technology we know works hooked up to a system that basically excepts all inputs? I can use floppy discs on my damn phone with some slight jiggering! lol
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Post by Paul Vanezis on Jan 6, 2019 22:52:58 GMT
It would be nice if someone could explain simply how they're getting a picture in 625, instead of telling us how poor the results are. 405 line video uses a longer line length than 625 and on the CV2000 the composite output is 1 volt. The method featured in the video takes the 1 volt output which is should be attentuated to reduce the voltage so that it's compatible with standard 625 composite video. That output goes into a 625 timebase corrector. The 405 lines (actually 377 active lines) will then occupy the top part of the 625 image. However, the issue is that it isn't really 377 lines, it's actually only 188 lines twice per frame as during record the CV2000 skips field two and on replay plays back the single recorded field twice. In effect, it's filmised video. In the demo video, you can see that the bottom redundant lines are cropped off and the 'squashed' 405 picture expanded to the correct 4x3 aspect ratio. The longer line length causes issues for most, if not all 625 TBC's which means that the right hand side of the image is cropped. The TBC is expecting 625 lines not 405 so dropout compensation won't work in the same way as it does for normal video. In the experiments I did, I got a lot of field jitter. I resolved this but shoving the tbc output through another VT machine and use the TBC in that to stabilise the field jitter. But the biggest problem of all is the highly unstable playback from CV2000 recorders. They just aren't very good. In an ideal world you need a virtually new machine and first generation recordings on then new tapes. Fortunately, I experimented with a player that had very few head hours and first generation recordings on 'once used' tapes so the playback was extremely stable. The obvious issues are dropouts causing sync errors and other playback issues which cause fields and frames to drop into the digital framestore of the TBC. Unfortunately, using this method, that side effect is inevitable. Paul
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Post by Sue Butcher on Jan 7, 2019 6:13:32 GMT
Thanks Paul, I think I understand the process now.
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Post by Simon B Kelly on Jan 7, 2019 12:00:27 GMT
Ideally, then, to correctly import CV-2000 recordings into a digital HD format, there needs to be a custom built 405-line Time Base Corrector designed to handle the longer line length stored in the 1-volt output so that all the information recorded for all 188 lines can be transferred across into a computer. The quality of the recordings so far suggests that they also need a Drop Out Compensation circuit to eliminate the white flashes, although there is probably software available these days that could do that at a later date.
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Post by Thomas Walsh on Jan 7, 2019 12:38:55 GMT
Zzzzzzzzzzzzzzzzz..........
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Post by John Gray on Jan 7, 2019 21:29:25 GMT
Brilliant news! I notice from the video that "Rod Stewart & Faces Maggie May" appears on one of the tape covers. For 47+ years I've been hoping that one of the missing performance would turn up (there are two wiped) - preferably the one of Rod in a yellow suit where the band all mime each others instruments - Woody (keyboards), Lane (drums), Mac + Kenney (bass / guitar). Absolutely hilarious and much more entertaining than the performance with John Peel. I'm almost embarrassed to say how much this performance means to me, I have been watching it in my minds eye ever since I was 11 years old! Does anyone else remember it?
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Post by Sue Butcher on Jan 7, 2019 23:36:02 GMT
Zzzzzzzzzzzzzzzzz.......... For want of a nail I'm staying awake. We'll lose early recordings like this if the technical problems aren't solved soon.
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Post by iwest on Jan 8, 2019 8:55:04 GMT
Chris did mention that they were building circuit boards specially for this project, which does suggest they're trying to do something bespoke and not simply put the signal through off-the-shelf gear.
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Post by John Marshall on Jan 8, 2019 17:08:02 GMT
These technical answers are all well and good but.....haven't we done this before? How have these tapes and nonsense line system been transfered and backed up in the past....because they have. Are we just dealing with an underfunded group with monetary and man power limitations? Is Kaleidoscope on patreon or something?! lol
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Post by aidanlunn on Jan 8, 2019 20:25:36 GMT
These technical answers are all well and good but.....haven't we done this before? How have these tapes and nonsense line system been transfered and backed up in the past....because they have. Are we just dealing with an underfunded group with monetary and man power limitations? Is Kaleidoscope on patreon or something?! lol The original 405 to 625-line converters developed in the 1960s are well out of service life (bespoke parts for them like transistors with switchable bases and collectors became hard to obtain by the early 1980s). The same fate befell the newer 405 to 625 converters developed by the BBC in the mid-80s. These were based around hardware that was available at the design stages, so to build one now with readily-available components means R&D and designing from the bottom up, just as the 1980s-developed converters did and the 1960s converters before them.
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Post by Paul Vanezis on Jan 8, 2019 20:43:59 GMT
These technical answers are all well and good but.....haven't we done this before? How have these tapes and nonsense line system been transfered and backed up in the past....because they have. Are we just dealing with an underfunded group with monetary and man power limitations? Is Kaleidoscope on patreon or something?! lol Unfortunately John, you are misinformed. There have been few truly transparent conversions of off-air 405 line material and the processes available to do it are all compromises. 405 to 625 conversions of broadcast material is possible still, but the original source material is very stable. What we're talking about is more a limitation of the format (CV2000) than 405 line video. The 405 line aspect just makes an already difficult job almost impossible. But in answer to your question (How have these tapes...been transferred and backed up in the past) the most common and reliable solution is to point a camera at a 405 line monitor. Obviously, that is not ideal. With regards, Paul
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Post by Simon B Kelly on Jan 8, 2019 20:58:36 GMT
The usual way of transferring CV-2000 tapes onto a modern format is by pointing a camera at a monitor and recording the picture. That was how they recovered the missing Steptoe and Son episode, "My Old Man's a Tory", and presumably the episode of TOTP from Lulu's collection was saved the same way. There has never been a proper converter, as far as I'm aware, for transferring 188-line domestic recordings. The old BBC gear would have been for professional broadcast recordings anyway, which wouldn't have the same stability issues that you get with 50-year old domestic reels of tapes...
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Post by garygraham on Jan 9, 2019 3:17:25 GMT
The BBC wasted £300 million on the failed Digital Media Initiative. Wouldn't that have been better spent manufacturing technology to do something like this and many other things? Also on manufacturing new heads for Panasonic D3 video recorders so they could continue playing those tapes? Or bunging Panasonic a few million to make hundreds more.
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