teletext

6 Articles

Teletext In Ireland, Another Broadcasting Leftover Bites The Dust

October 13, 2023 by 14 Comments

Over the years we’ve reported on the passing of a few of the broadcasting technologies of yesteryear, such as analogue TV in America, or AM radio in Europe. Now it’s the turn of an early digital contender, as one of the few remaining holdouts of old-style teletext is to shut down its service. The Irish broadcaster RTÉ is to turn off its teletext service Aertel, which has been live in some form continuously since 1986.

Like all European countries, Ireland has had only digital TV for quite a few years now. The linked RTÉ piece implies that the Aertel service has been carried as the old-style data in the frame blanking period even when part of a digital multiplex rather than the newer digital teletext system, so we’d be really grateful if some of our Irish readers could flick on their TVs and confirm that.

In an internet-connected world it seems quaint that a limited set of curated pages could once have been such a big deal, but it’s easy to forget that for many the teletext system provided their first ever taste of online information. As it shuffles away almost unnoticed we won’t miss counting through the page numbers cycling by in the top corner as we waited for our page to load, but it’s worth marking its final passing from one of the few places it could still be found.

Teletext does pop up in a few projects here, most recently as the display engine for a game of DOOM.

It’s DOOM, But In Teletext

May 20, 2023 by 21 Comments

We’ve seen the 1993 id Software classic DOOM running on so many pieces of unexpected hardware, as “Will it run DOOM?” has become something of a test for any new device. But will it run in the circuitry of a 1970s or 1980s TV set? Not quite, but as [lukneu] has demonstrated, it is possible to render the game using the set’s inbuilt Teletext decoder.

Teletext is a technology past its zenith and which is no longer broadcast in many countries, but for those unfamiliar it’s an information service broadcast in the unseen lines hidden in the frame blanking period of an analogue TV transmission. Its serial data packets can contain both pages of text and rudimentary block graphics, and we’re surprised to learn, can include continuous streams to a single page. It’s this feature that he’s used, piping the game’s graphics as a teletext stream which is decoded by the CRT TV and displayed as a playable if blocky game.

Delving further, we find that DOOM is running on a Linux machine on which the teletext stream is created, and the stream is then piped to a Raspberry Pi which does the encoding on to its composite video output. More powerful versions of the Pi can run both processes on the same machine. The result can be seen in the video below, and we can definitely say it would have been mind-blowing, back when DOOM was king. There are plans for further refinement, of which we’d say that color would be the most welcome.

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CEEFAX Lives! (Courtesy Of A Raspberry Pi)

January 7, 2022 by 28 Comments

As analogue TV slides from memory, there’s a facet of it that’s fondly remembered by a band of enthusiasts. Teletext was an electronic viewdata information service digitally encoded in the frame blanking period, and a TV set with a decoder chip would provide access to many pages of news and other services all displayed in the characteristic brightly colored block graphics. It went the way of the dinosaur with the demise of analog TV, but for [Nathan Dane] the flame is kept alive with his own private version of the BBC’s CEEFAX service.

He has a particular enthusiasm for analog TV, and as such has his own in-house channel served by a UHF modulator. He shares with us the story of how he arrived at a teletext service, before writing code to scrape the BBC news and weather websites and populate his modern-day CEEFAX. Behind it all is a Raspberry Pi, with a vbit-pi board injecting the teletext signal onto the video, and raspi-teletext creating the pages from source material derived from a set of custom scraper scripts.

We like this project a lot, because while it’s not the first Pi teletext system we’ve encountered, the use of a scraped live feed makes it one of the most creative.

Thanks [kwikius] for the tip!

History Of Closed Captions: The Analog Era

April 14, 2021 by 46 Comments

Closed captioning on television and subtitles on DVD, Blu-ray, and streaming media are taken for granted today. But it wasn’t always so. In fact, it was quite a struggle for captioning to become commonplace. Back in the early 2000s, I unexpectedly found myself involved in a variety of closed captioning projects, both designing hardware and consulting with engineering teams at various consumer electronics manufacturers. I may have been the last engineer working with analog captioning as everyone else moved on to digital.

But before digging in, there is a lot of confusing and imprecise language floating around on this topic. Let’s establish some definitions. I often use the word captioning which encompasses both closed captions and subtitles:

Closed Captions: Transmitted in a non-visible manner as textual data. Usually they can be enabled or disabled by the user. In the NTSC system, it’s often referred to as Line 21, since it was transmitted on video line number 21 in the Vertical Blanking Interval (VBI).
Subtitles: Rendered in a graphical format and overlaid onto the video / film. Usually they cannot be turned off. Also called open or hard captions.

The text contained in captions generally falls into one of three categories. Pure dialogue (nothing more) is often the style of captioning you see in subtitles on a DVD or Blu-ray. Ordinary captioning includes the dialogue, but with the addition of occasional cues for music or a non-visible event (a doorbell ringing, for example). Finally, “Subtitles for the Deaf or Hard-of-hearing” (SDH) is a more verbose style that adds even more descriptive information about the program, including the speaker’s name, off-camera events, etc.

Roughly speaking, closed captions are targeting the deaf and hard of hearing audience. Subtitles are targeting an audience who can hear the program but want to view the dialogue for some reason, like understanding a foreign movie or learning a new language.

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Relive The Glory Days Of Cable TV With This Retro Weather Feed

February 21, 2020 by 43 Comments

This may surprise younger readers, but there was once a time when the reality programming on The Weather Channel was simply, you know, weather. It used to be no more than a ten-minute wait to “Local on the Eights”, with simple text crawls of local conditions and forecasts that looked like they were taken straight from the National Weather Service feed. Those were the days, and sadly they seem to be gone forever.

Or perhaps not, if this retro weather channel feed has anything to say about it. It’s the product of [probnot] and consists of a simple Python program that runs on a Raspberry Pi. Being from Winnipeg, [probnot] is tapping into Environment Canada for local weather data, but it should be easy enough to modify to use your local weather provider’s API. The screen is full of retro goodness, from the simple color scheme to the blocky white text; the digital clock and local news crawl at the bottom complete the old school experience. It doesn’t appear that the code supports the period-correct smooth jazz saxophone, but that too should be a simple modification.

All jibing aside, this would be a welcome addition to the morning routine. And for the full retro ride, why not consider putting it in an old TV case?

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Teletext On A Raspi With Zero Additional Parts

February 13, 2015 by 45 Comments

Way back in the 70s, the UK and BBC rolled out teletext – an information retrieval service that’s much closer to the ‘television screens connected to computers the size of a room’ popularized by 1960s futurists than the Internet and world wide web. For about 30 years, teletext was one of the most reliable means of information distribution until it was quietly shelved with the rollout of digital television.

Playing with dead protocols is fun, though, and since the Raspberry Pi has an analog video out, [Alistair] thought it would be fun to turn his Pi into a teletext generator and display.

This isn’t [Alistair]’s first teletext rodeo; earlier he built an add-on board for the Raspi that uses an AVR and an LM1881 video sync separator to mux the video output of a Raspi with teletext signals. The new build does away with this completely, allowing any Raspberry Pi to generate and display information from a teletext service. Right now there are two demos, a Raspi status display that shows the CPU frequency, usage, memory, and temperature. There’s also a ‘clock cracker’ with a picture of Tux that should help diagnose reception issues.

All the code is available on the project’s github, although [Alistair] hasn’t released the scripts to output teletext pages captured from broadcast signals years ago.

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