[vdr] Subtitle recording

[Dave Chapman <dave@dchapman.com>]

Is there any interest in adding subtitle recording (and obviously display in 
the future) to VDR?  As with AC3 audio, it would be nice to implement 
recording in advance of decoding and display functionality in VDR.

There are two types of subtitles used in DVB broadcasts - teletext and DVB 
subtitles (ETS 300 743).  Teletext subtitles are relatively simple to decode, 
but DVB subtitles are a lot more complex.

In the case of teletext subtitles, the PID is already in the channels.conf 
file and recording the teletext stream would record any subtitles including 
in that stream.

I can't find any channels on Astra 19 or Astra 28 that use the new, 
bitmap-based DVB subtitles.  However, they are used with DVB-T broadcasts in 
the UK, which is where I make all my recordings from.  These are broadcast on 
a separate PID and this information would need to be added to the 
channels.conf file, maybe separated by a semi-colon in the teletext field.

There is also meta-information (in the DVB-SI) sometimes broadcast with both 
teletext and DVB subtitles, including the language of the subtitles and, in 
the case of teletext, which page they appear on.  This would probably be lost 
(unless stored in a separate file), but would not be a major problem.

Would it be a large change to VDR to enable this kind of recording of "data" 
streams?  It would add a small amount to the size of the recorded files, but 
could easily be disabled.

Any comments?

Dave.