History Of Closed Captions: The Analog Era

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

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

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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