[xine-devel] MPEG-2 closed caption decoding

[<cv...@gr...>]

Hello,

I hacked some preliminary proof-of-concept code for the xine version
of libmpeg2 that decodes closed captions, as they are found in DVD
MPEG-2 streams. Right now it does not do anything except dump the
captions to the console. I would like to help transforming this code
into full-featured closed captioning support for xine.

This issue is rather dear to my heart, as I have a profound hearing
loss and cannot understand movies without captions at all. I am happy
with xine's subtitling support, but there are many movies that have
only closed captions, as opposed to subtitles, and in some cases where
both are available, the closed captions are more comprehensive.

The way my code works right now is:

1. decode libmpeg2 userdata fields

2. Peel out Line 21 captioning information from decoded userdata fields

3. Decode Line 21 information into positioning/control/text information

4. Dump captions to console

Right now, I have everything in the libmepg2 module, but it seems to
me that only step 1, and maybe step 2 should be done there. Steps 3
and steps 4 should be general enough to work with a wide array of data
formats.

I would appreciate any discussion or hints on how the steps involved
in decoding and displaying the captions should be divided between
libmpeg2 and xine, and whether the xine infrastructure would aready
support this kind of thing. I can also send in a patch with the code
as it is now if you think that it will help.

- Christian