Engineering Asked by Rondall H. on February 12, 2021
Ever since I was a kid in the 1990s, I’ve been wondering about this. I have never been able to verify/test it in a conclusive manner.
It may be almost forgotten now, but in those days, each TV channel (at least in Sweden) had a "hidden interface" in the shape of "Text-TV" ("Teletext") which would show a fullscreen "terminal"-style dump of information, allowing the user to "surf" this primitive "Internet for poor people" by entering numbers such as "123". You then had to wait a certain amount of time and then could see that "page".
Obviously, this was accomplished by some sort of hidden metadata being sent along with the video/audio data, and the waiting was necessary because it only sent some "pages" of data at a time due to bandwidth limitations.
My question is: if you recorded such a broadcast onto a VHS tape with a normal VCR, then later looked at the video tape, would the TV allow you to enter and "surf around" the Teletext, just as if it had been "live"?
Or was this data scrapped and never made it onto the VHS tape? Or was it included, but some other reason made it impossible to (easily) "surf" it later?
This is not a direct answer to your question since my experience is only with US based closed captioning. I hope that is at least somewhat related.
My VHS recorder that bought as an adult (gee, am I that old?) recorded whatever NTSC it received on its tuner. I don't know about PAL but United States closed captioning was broadcast during the vertical blanking interval and since VHS was analog, whatever was broadcast was what was recorded. Whether it is useful to the decoder is another matter. The recorder is designed to reproduce what it expects. If whatever is not expected gets reproduced, that is a bonus, but not required.
The US started requiring closed captioning decoders to be added to new TVs in 1993. The networks had been broadcasting closed captioning for sometime before that. I'll have to
This sounds like a good New Years Day project. We'll see if it gets done.
Answered by user1683793 on February 12, 2021
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