[mythtv-users] Re: subtitles Re: Reuters: FCC Overstepped Authority on Digital TV

Martin Barnasconi mythtv at barnasconi.net
Tue Mar 1 21:03:36 UTC 2005


> Well, MPEGs *can* have subtitle information embedded, AFAIK. Whether or 
> not a particular content producer embeds them is another story. Right 
> now I don't think Myth supports MPEG subtitles, but the point is the 
> information *should* be there and accessible by standard consumer 
> devices**... perhaps someone familiar with the Americans with 
> Disabilities Act could shed some light. 

Current status is that for PVR cards using the IVTV driver, the sliced 
vertical blanking interval (VBI) stream, containing teletext/subtitles/CC,  
is now embedded in the MPEG2 program stream (PS). Note that this embedding is 
IVTV driver specific. VBI Decoding support in mythtv is in process.
For DVB MPEG transport streams (TS), VBI has its own PID and should be 
detected differently. Similar approach, but you need a different detection 
procedure here.

> Not necessarily. AFAIK only Myth has the ability to record VBI data and 
> convert it to subtitles for display afterwards. I doubt ReplayTV or 
> Tivo can do this. (NB- Myth only supports this currently for analog 
> framegrabber (bttv) cards), though support the VBI interface on ivtv 
> cards is maturing, so Myth may support them at some point, too. 

Yes, non-hardware-encoder cards like bttv and saa7124 support vbi in a limited 
way (subtitles/CC only; no teletext).
IVTV vbi decoding support is on its way....

just curious...How are the subtitles embedded in the ReplayTV data?

Martin


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