[mythtv] [PATCH] More CC stuff

Gregorio Gervasio, Jr. gtgj at pacbell.net
Tue Mar 30 05:15:55 EST 2004

        A few more fixes:

- Fixed display of multiple backspace codes.  Sorry, there was a
mistake in my previous patch.

- Avoided encoding too many redundant erase codes.  Some stations spit
out long streams of erase codes and this was overflowing the frontend.

- Misc. cleanup for switching caption styles, missing address codes.

New stuff:

- I was misled by some article that implied that TXT1 is CC3.  This is
not true -- CC3/4 and TXT3/4 are separate streams on field 2 of VBI
line 21.  Anyway, I added processing of these streams so that CC[1-4]
and TXT[1-4] are available.

- More fixes to TXT streams.  The list of control codes to exit TXT
mode were incomplete.  Also, since TXT mode can display up to 15
lines of text, I moved some of the display processing to osdtypes.cpp
so that NVP doesn't have to keep a copy of the same 15 lines of text.
I think this may also make things easier if we want to add things like
italics and smooth scrolling.

        I finally found some detailed documentation for CC codes:


I wish I had seen this much earlier.  Anyway, I think I'm done adding
new stuff so if anyone wants to take a shot at adding colors,
italics, and blinking ...

        There's also information on that page for decoding XDS
packets and ITV (WebTV) links if anyone is interested.  XDS packets
(which I currently skip) contain things like V-Chip control codes,
program/station ID, time of day, weather, ...  I'm guessing that TiVo
thumbs-up/down codes are also sent as XDS packets.  ITV links are in
TXT streams and my patch just displays these as raw text.

        If anyone knows of shows that frequently use CC[2-4] and
TXT[1-4], let me know so I can do some more checking.  I think CC2 is
okay -- I've seen it used for Spanish captions on "The Tonight Show"
and for kid's captions (simpler words :-)) on some PBS shows.  I've
only seen CC3 used in short segments on Spanish channels and as copies
of CC1 in some ads.  I've only seen ITV links on TXT[1-2] in some

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Gregorio Gervasio, Jr.

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