Date   : Tue, 09 Jun 2009 14:51:32 +0100
From   : tim.fardell@... (Tim Fardell)
Subject: Morley Teletext Adapter

In the early days of SkyDigital in the UK (when I made the dreadful 
mistake of subscribing to it for a year) a lot of the digital channels 
carried "analogue" teletext, but my TV would not display this if I set 
the box to output RGB. I had to set the box to Composite to watch 
Teletext.

I also remember one obscure channel on Terrestrial digital TV (back in 
the ONdigital days) used to carry a teletext signal, but nowadays I 
don't think any do.

michael.firth@... wrote:
>> -----Original Message-----
>> From: 
>> bbc-micro-bounces+michael.firth=bt.com@... 
>> [mailto:bbc-micro-bounces+michael.firth=bt.com@...
>> .uk] On Behalf Of Andrew Benham
>> Sent: 09 June 2009 14:02
>> To: Joel Rowbottom
>> Cc: bbc-micro@...
>> Subject: Re: [BBC-Micro] Morley Teletext Adapter
>>
>> Joel Rowbottom wrote:
>>> Hi Anders --
>>>
>>> On Tue, 9 Jun 2009 14:35:29 +0200, "Anders Carlsson"
>>> <anders.carlsson@...> wrote:
>>>
>>>> While I don't have a clue how digital broadcasts work in 
>> the UK, I am
>>>> fairly 
>>>> positive the DVB aerial broadcasts here in Sweden still 
>> carry a teletext 
>>>> signal.
>>> I know some satellite (DVB-S) services still carry analogue teletext
>>> transmissions, so I have no reason to believe DVB-T would 
>> be any different.
>>
>> DVB-T, at least in the UK, doesn't have the same sort of 
>> teletext.  Analogue
>> TV has teletext signals on certain lines in the vertical 
>> blanking interval.
>>
>> DVB-T has MHEG-5 data contained in carousels which are on 
>> declared pids in
>> the data stream.  (Sorry for the abbreviation soup).
>> The upside is that programmes aren't restricted to a specific 
>> set of characters
>> and graphics.  The downside is that one needs to do at lot 
>> more to decode
>> and display it.
>>
> The standard exists for the carriage of Teletext over DVB-T (or indeed
any other MPEG) broadcasts -the DVB/ETSI standard is ETS 300 472.
> 
> However, in the UK I think broadcasters are discouraged from using this,
as MHEG-5 is the preferred approach.
> 
> For other countries, support for this standard is mandated for the STBs,
so I'm sure that UK STBs will support it - its just that most of the broadcasters
don't.
> 
> As an aside, several of the analogue channels are carried as MPEG video
to the transmitter sites these days, including part of the Teletext service.
> 
> Regards
> 
> Michael
> 
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