Date   : Sat, 18 Jul 2009 21:40:29 +0200
From   : rick@... (Rick Murray)
Subject: Fw: Fwd: ITV Teletext to shut down in January

Jonathan Graham Harston wrote:

> Even if you're just tranmitting the 12 scan-lines that contain
> teletext data, you can't just not transmit the other 613 lines.
> Even if you could somehow set up a system that only transmitted 12
> scanlines each second, that would occupy the whole of a UHF TV
> transmission slot for 0.0192s each second.

You are missing though that teletext information is handled separately 
with digital broadcasts (it can't be compressed using a lossy system!). 
When analogue shuts down, all the stuff with PAL signals and scanlines 
will no longer be relevant as it will be your receiver generating the 
signal - hence the teletext data WILL be additional bandwidth, though 
I'd be quite willing to wager that teletext overheads would be almost 
negligible compared to interactive... forget not that BBC (on satellite) 
is carrying TWO interactive streams - there's the feature-rich OpenTV 
system for Sky boxes, and the little-brother MHEG version for FreeSat. 
Oh, and each of the BBC regions plus the other BBC channels) are all 
carrying copies. A staggering amount of non-picture data. And teletext 
amounts to what in the face of this?

I think mass-market appeal is thinking like the Americans (who never 
really took to teletext) in that digital interactive is flash and glossy 
and look at the capabilities for different text styles, picture 
inserts... while completely missing that teletext while not altogether 
quick and looking like an '80s computer was straight to the point and 
astonishingly simple to navigate... Unlike BBCi where it is only indexes 
that have numbers, which may be three or four digits long. Accordingly, 
neither FreeSat nor Sky Digibox offer any built-in teletext. The Sky box 
inserts it into the VBI, probably as a necessity for subtitling only 
being available on teletext in the early days. Can't say if FreeSat does 
the VBI thing, not tried.

So it seems that now may be the time to start thinking about a little 
teletext encoder for old time's sake. If somebody can make a WiFi 
antenna out of an old Pringles tube [*], then a teletext inserter based 
around a microcontroller and a wodge of memory shouldn't be impossible!


Best wishes,

Rick.


* - http://www.oreillynet.com/cs/weblog/view/wlg/448///

-- 
Rick Murray, irregular internet access at local library.
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...