[mythtv] [experimental patch] Teletext decoder for DVB Cards

[Frank Muenchow]

Here is the first experimental patch for decoding Teletext for 
DVB-Cards. (It's far away from being perfect, but you're welcome to 
contribute to improve the code or to find errors)

It uses the vbi decoder patch for ivtv-cards (see 
http://mythtv.org/pipermail/mythtv-dev/2005-March/032905.html ), so 
there are the same TODO's and problems...

It works for me in Duesseldorf, Germany using DVB-T.

------------------------- snip -----------------------------------------
What it does not do yet (TODO ;-)
- It overrules the 'T' key for teletext/CC for non-encoder cards
(bttv/saa7134) . The original vbi code (part of nuppelvideoplayer/recorder)
is still in, but I rather see this becoming part of this new vbidecoder
class. Like to see 'C' for CC/subtitles and 'T' for teletext. Problem: 'C'
function already in use...
As some people have a mixed PVR/bttv setup, we should detect which card is
operational and select the correct vbi decoder.
...
- Teletext is text-only. No mosaic or other fancy stuff like blanking, 
FLOF,
blicking, reveal functions yet. Uses current CC_font in OSD. Should be
teletext font in future. for the OSD overlay, we suffer from the color
mapping of YUV420 here. Use a font with sufficient width (eg bold fonts) to
be able to read the blue or red text.
...
- TT OSD overlay is not transparent. Future work is to have black,
transparent, or even left-TV/right-TT (for 16:9 screens) or TT-PIP
implemented (for big screens)

- no bit error detection

Give it a try and report your findings. Improvements are very welcome.



Frank



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