[mythtv] Closed Captioning & Teletext/Videotext

Henk Poley hpoley at dds.nl
Fri Jan 17 17:09:16 EST 2003


> Van: Erik Arendse <erik_nospam.arendse at bigfoot.com>
>> At 15-1-03 07:55, Henk Poley wrote:
>>
>>> I am busy implementing Closed Captioning support and support for
>>> European Teletext/VideoText (used for 1000 sorts of info, including
>>> Closed Captioning).
>>
>> Actually max. 899 sorts of things ;-)
>> Pages lower than 100 and higher than 999 don't exist.
>
> You forget sub-pages... :-)

Uh yea, I did... :o)
 
>>> As a by-product mythtv will have 100% buffered teletext/videotext
>>> support from the current selected channel, not timeshifted, but that
>>> would be a bit too much effort only to display a timeshifted clock :-)
>>
>> Uh, how are you going to sync subtitles (?Closed Captioning?) then?
>
> Close Captioning is separate from the rest of my engine, it's just that
> as I included the teletext decoder it  will be only so much work to show
> all pages. Not fully implemented yet, but it will be.

So you "magicaly" know what Teletext page is used for CC? I know that
most channels use page 888, but not all. I seem te remember channels that
use _different_ pages for different programs.

> CC is added to the recorded file in a new type of CC-frame, it's only a
> few lines every few seconds.

It could even be witten as an MPEG4 Closed Captioning stream, when
recording with DivX. AFAIK, MPEG4 has standardized subtitles, isn't it?

> Adding Teletext to the recorded file would be a 
> load of data for no use (why would anyone read shifted or recorded
> teletext?)

Doing just a "streamed" diff would slowdown the playback (fast-forward,
rewind) process, isn't it?

	Henk Poley <><


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