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Old 11th Jan 2019, 7:37 pm   #1
2ombieboy
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Default External Teletext Decoder. Is there such a thing?

Hi guys looking to capture pages from teletext from laserdisc and vhs/Betamax tapes. but modern pcs just carnt do it. was there ever a box that would sit on a none teletext tv and push a teletext signal to it so an old set could be used. rf in and out. and you could control it with a remote or key pad/button press. or was there an old say windows 98/xp computer capture card that would capture teletext not just display it.


not sure if such things exsist just want to archive myt tapes and laserdiscs


Alan
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Old 11th Jan 2019, 7:40 pm   #2
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Default Re: external teletext decoder. is there such a thing

ISTR a number of hobby magazines had DIY Teletext decoders - ETI magazine springs to mind as one, Wireless World (potentially) another.

http://teletext.mb21.co.uk/timeline/eti-decoder/

So yes, they do (did) exist. I'm surprised there isn't some software and interface that doesn't do it - could swear I've seen or read about such......

But, even if you wanted to go the DIY route I doubt you'd find the specialised IC's any more.
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Old 11th Jan 2019, 7:46 pm   #3
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Default Re: external teletext decoder. is there such a thing

the only stuff I can see is for lynux and rasbery pi and I don't have the first clue on how to use them. I was thinking would a old on digital box work as I am sure it had both tuners on digital and analogue

Thanks for the link I will take a look

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Old 11th Jan 2019, 7:48 pm   #4
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Default Re: external teletext decoder. is there such a thing

I built the design in Television (I think it was Television check later )in the late 70's

Most video recorders ISTR didn't record the Teletext info although you could get recorders that did IIRC.

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Old 11th Jan 2019, 8:06 pm   #5
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Default Re: external teletext decoder. is there such a thing

all I need it to do is decode the signal and let me control it the pc with its video capture card will do the capturing of it.
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Old 11th Jan 2019, 8:10 pm   #6
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Default Re: external teletext decoder. is there such a thing

Did Manor Supplies sell one?
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Old 11th Jan 2019, 8:19 pm   #7
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Default Re: external teletext decoder. is there such a thing

Yes there are several machines - I used to have 3 of them made by AYR. I adapted for video/audio out and fed that into a vhs recorder. Used for recording subtitles onto video for deaf people.

My best recommendation would be to get a Hauppauge cord for a pc that should work.

or you could use the BBC teletext adaptor and a BBC micro to capture.

There has also been various attempts to get data from VHS video tapes to recover teletext signals - maybe worth looking at that. (try www.glasstty.com).
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Old 11th Jan 2019, 8:27 pm   #8
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Default Re: external teletext decoder. is there such a thing

Bear in mind though that not all VHS machines recorded the Teletext information successfully. I can remember trying to display the Teletext on my then Teletext-equipped TV from an off-air VHS recording and failing dismally.
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Old 11th Jan 2019, 8:40 pm   #9
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Default Re: external teletext decoder. is there such a thing

I bought a PC at a sale, inside was an 8 bit ISA board by SYNAPSYS Ltd inSERT Teletext Encoder.

The reason I kept the board was that it used a TI TMS34010, which 30+ years ago was a high end graphics chip. I used the simpler 34061 in many designs and kept this for old times sake.

The board has the processor, DIMM RAM, SRAM, delay line, odd logic and two BNC connectors. Note, no software!

It is now hovering over the scrap bin having had no luck selling it to anyone for the 34010.
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Old 11th Jan 2019, 8:43 pm   #10
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Default Re: external teletext decoder. is there such a thing

Quote:
Originally Posted by Dave Moll View Post
Bear in mind though that not all VHS machines recorded the Teletext information successfully. I can remember trying to display the Teletext on my then Teletext-equipped TV from an off-air VHS recording and failing dismally.
I want to start not with the vhs stuff but the laserdiscs I can get all the pages fine on my tv but just carnt get a clean recording only by using my phone

ile show a video bellow of it in action hope that link works

https://youtu.be/6vuTojODXeU
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Old 11th Jan 2019, 8:49 pm   #11
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Default Re: external teletext decoder. is there such a thing

I seem to recall that there were some professional decoders about but most people (those that could) went down the DIY route. Manor Supplies in London were selling Mullard teletext boards and kits to build your own. Nothing like that available now of course since there is no analogue text anymore although it might be worth checking eBay.
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Old 11th Jan 2019, 8:52 pm   #12
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Default Re: external teletext decoder. is there such a thing

I remember the S-VHS machines could record the teletext signal so you could look around for a good second-hand S-VHS video.
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Old 11th Jan 2019, 9:03 pm   #13
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Default Re: External Teletext Decoder. Is there such a thing?

There were a handful of stand-alone Teletext decoders made for professional use, one example being the Shootview VIP011 (also sold under the DT brand), a 1U box with switchable PAL composite sources in and RGB outputs. If you can find any offered in the usual places, I don't suppose that many people will be clamouring for them (though, as with anything that exists in small numbers, what happens on the day can be unpredictable!).
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Old 11th Jan 2019, 9:18 pm   #14
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Default Re: External Teletext Decoder. Is there such a thing?

SVHS and, I think Betamax, would reliably record teletext. My understanding is that this was never mentioned by the makers because it would have been incitement to infringe copyright in the content of the pages. There was a teletext page which advised users that copyright existed and copying the pages was illegal. This could be a factor in the scarcity of published info about how it could be done.

I did find I could sometimes recover poor quality teletext from tapes recoded on my first VCR ( a single-speed Mitsubishi B12), but success was random. Cheap tapes (Comet own brand) sometimes worked when more expensive ones didn't. I had no success playing the same tapes in other VCRs.
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Old 11th Jan 2019, 10:06 pm   #15
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Default Re: External Teletext Decoder. Is there such a thing?

I remember when I was at Philips, they marketed a VHS machine with a teletext decoder and made a great deal of the fact that this enabled deaf people to record subtitles on 888 along with the program. The machine would effectively embed the subtitles into the video recording with the advantage that they could be played back on any other video (since the subtitles were then part of the video recording). The machine could also be used as a teletext receiver and used with a non-teletext set.

They also marketed an S-VHS machine that recorded the teletext signal 'on the fly' with the video recording so to speak so that the recording could be played back on any TV with teletext and the TV would respond to the recorded text signal as if it was live. It could be quite interesting playing a two year old tape, switching to teletext and seeing old news items from when the tape was recorded. 888 could also be selected for subtitles.
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Old 11th Jan 2019, 10:08 pm   #16
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Default Re: external teletext decoder. is there such a thing

Quote:
Originally Posted by Cobaltblue View Post
I built the design in Television (I think it was Television check later )in the late 70's

Most video recorders ISTR didn't record the Teletext info although you could get recorders that did IIRC.

Cheers

Mike T
Most of them recorded Teletext data, they couldn't help it unless they blanked the VBI. Whether it was possible to reliably decode the data when played back was a different matter, due to poor recovered eye-height.

Standard Play VHS was tantalisingly close, and the header row reproduced reasonably well (because of additional error correction) but the body of the page, if it appeared, at all was usually full of errors.

s-VHS could give results

I never tried Betamax but its faster writing speed and resolution may have pushed in the right direction.

Some VHS machines decoded the teletext internally, so it could burn in 888 subtitles, and make use of the programme schedule pages, but that's a separate matter.
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Old 11th Jan 2019, 10:49 pm   #17
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Default Re: External Teletext Decoder. Is there such a thing?

Yes the actual data was just on lines at the top of the scan not normally seen altbough you could see it if you reduced the height on some sets others were still blanked by frsme flyback

They increased the number of lines the data was on to increase the speed of page selection and you could see it some of the sets we had at the top of the picture.

If I remember correctly it started with two lines I well remember the clock cracker page to help you set up the clock recovery circuit.

When the chip sets came out it reduced my 100 + bug wire wrapped monstrosity with pages selected by thumbwheel switches to a few LSI chips.

Never had much success with recovering TT from recordings myself the error rate was usually too high but it did work better toward the end of the period when I think they used more lines 8 Seems to ring a bell.

Cheers

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Old 11th Jan 2019, 11:08 pm   #18
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Default Re: External Teletext Decoder. Is there such a thing?

While working for a small independent Ferguson dealer in the late 80s earley 90s I remember one of the Thompson made FV series VHS machines that could record 888 subtitle pages on top of the picture, but I don't think you could record other pages.

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Old 11th Jan 2019, 11:12 pm   #19
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Default Re: External Teletext Decoder. Is there such a thing?

If I remember correctly, the Television magazine design cut a lot of corners, monochrome graphics, and pages selected by DIP switches. There was one built into a set at the Granada TV Rentals training department in Bedford, and was the first Teletext set I played with.
The Wireless World design by comparison was full spec for the time, but I suppose when the Broadcast Teletext specification was changed with the inclusion of Double height characters etc these too would have been rendered useless, as indeed the commercial Texas Instruments (TIFax) decoder fitted to the first Salora TT set was rendered useless.

<Edit> Correction: Thumb-wheel switches not DIP switches.
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Last edited by rambo1152; 11th Jan 2019 at 11:19 pm. Reason: re-read Mike's post.
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Old 11th Jan 2019, 11:59 pm   #20
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Default Re: External Teletext Decoder. Is there such a thing?

Reading about the Philips machine mentioned in #15 reminded me that we had a similar Grundig VCR that had a teletext decoder built in, and could burn subtitles on to recordings. It could also be used to bring teletext to non-text TV sets, although the picture was PAL, so nowhere near as nice to look at. It used a Panasonic G deck. I remember that it was an absolute pig to drive - the user interface was a real horror, so my parents just used it as a basic VCR - and it was very unreliable. I think we only got 2 or 3 years of use from it before giving up on it.

Recording teletext was possible on my Panasonic FS-88 S-VHS machine, but it relied on the correct setting of the picture sharpness control to get a reliably recoverable signal. Tapes had to be played back in the same machine for best results (I ended up with 2 or 3 of these machines eventually). Never managed it with any hint of reliability in any standard VHS machine - just not enough video bandwidth.

Never tried it on Betamax, but V2000 was slightly better than regular VHS, for what that's worth

I'd say that if you have a good video signal that gives reliable results on a teletext TV set, then the BBC Micro plus teletext adaptor is a good way to go. But then, I have those here, so I guess I would say that . Saved images can be transferred via a serial cable to a PC and displayed on a BBC emulator, then captured as a screengrab in Windows. It would be time-consuming, but the results would look good. Otherwise, you might as well just photograph the screen of the TV. With a bit of experimentation, the results from that can actually be quite good. It just depends on what you want to achieve.

In years gone by, I remember manually creating copies of teletext pages character by character using a MODE7 editor that I wrote. Getting the graphics done was sometimes tricky, but it was a good way to learn new ways to do things with the limited teletext graphics characters. I still have them, and occasionally dig the disc out for a bit of nostalgia. I wish I'd made more, but it was extremely time-consuming - though a good way of passing the time as a bored teenager. Those were the days
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