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Apr 19 2012

Have you retuned your TV yet?

Today, April 18, marks the passing of analogue TV into the annals of time. Well, at least, in the London area.

On April 4, 2012, BBC2 was switched off, and today, the rest of the channels follow, leaving all your TV stations on digital only (Freeview, Sky, Freesat, cable, Virgin, etc). You now need to retune your freeview box to pick up any changes and any additional channels now becoming available once the signal strength has increased.

Today also marks the end of CEEFAX, the last digital teletext service in the UK.  As The Register says:

Over a decade ago the majority of UK holidays were booked by TV, but today London lost Ceefax – and by the end of the year teletext as we know it will disappear entirely.

Ceefax is the BBC’s teletext service, as opposed to the eponymous Teletext Limited, which produced text services for the other channels from 1993 to 2010, and sold so many holidays, but both services came embedded in the analogue TV signal. That signal is vanished from the capital this morning, so anyone wanting badly-rendered text on a TV will have to move to Northern Ireland or use Google TV instead.

Analogue television is transmitted in blocks of lines, but not continuously. The magnets guiding the stream of electrons can’t switch instantly, so the signal is paused at the end of each line to give the magnets time to aim the stream at the start of the next line. That gives a Horizontal Blanking Interval (HBI), but it’s pretty short, much longer is the Vertical equivalent as the aim has to be shifted up as well as across the screen.

When it was launched, back in 1974, Ceefax used to top few lines of the normal transmission (which aren’t generally visible on a CRT), but later it slipped into the VBI pause in line with international standards. The US never really got teletext; Americans did put watermarking and V-Chip information into the same gap, but they lacked the monolithic BBC which could dictate a standard and ensure commercial partners conformed to it.

Back in the late ’90s, teletext compared well to the rapidly growing WebTV service: putting the two side-by-side, WebTV was clearly more interactive, but teletext was more legible. And if you wanted to book a holiday than Teletext was the platform of choice. Holidays really took off on Teletext, with its ability to list late bargains, so much so that TeletextHolidays is still a successful business despite the transmission medium having vanished two years ago.

Digital television does support text, complete with picture-in-picture and much better fonts. Digital text is composed in MHEG, sent out on a separate channel as digital pictures leave no pauses in which to insert supplementary data, but the technical improvements can’t disguise the lack of character and content.

 

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