[mythtv-users] VBI subtitles with ivtv cards?

[Jesse Guardiani]

Mark Cooke wrote:
> On Fri, 2005-09-23 at 10:19 -0400, Jesse Guardiani wrote:
>   
>> Joseph A. Caputo wrote:
>>     
>>> On Thursday 22 September 2005 16:37, Isaac Richards wrote:
>>>   
>>>       
>>>> On Thursday 22 September 2005 04:29 pm, Joseph A. Caputo wrote:
>>>>         
>>> So does that mean that they'll get embedded in the MPEG file, but Myth 
>>> just can't parse them out yet?
>>>
>>> - Are they muxed into the MPEG in a standard way (i.e., could I view 
>>> them with another program (mplayer, xine, etc)? )
>>>       
>> AFAIK. In fact, projectx doesn't seem to have any problem demuxing the 
>> mpegs either.
>> I've burned several VBI laden mpegs to DVD using mythburn without any 
>> problems.
>>     
>
> The subtitles (and other VBI data) are muxed in using a private stream,
> in an IVTV specific format by the IVTV driver (in ivtv-vbi.c).
>
> The ivtv muxer breaks program-stream assumptions made in transcode about
> the size of each stream unit being exactly 2048 bytes long.  Word was
> that the 2048 byte unit size is specified in the MPEG spec, but I
> haven't had time to plough through the docs yet.  I just wrote a
> subtitle-stripper that I used before transcoding for storage.
>   


What version of ivtv were you using when this happened? The recent 0.3.8 
fixes an issue
that sounds identical to this. The issue causes projectx to take FOREVER 
to process an mpeg
file. Not only does the 0.3.8 version apparently fix the problem, but 
there is a program
called packfix available to repair your existing mpeg files:
    http://www.gossamer-threads.com/lists/ivtv/devel/24204

As I mentioned before, I use mythburn on mpegs with embedded VBI without 
any problems,
and mythburn uses transcode to grab thumbnail images from the stream, so 
it's possible that
the two issues are related/fixed.


[...]

> Hans did state a long term goal of providing standards-based VBI data in
> the IVTV stream on the IVTV list (or maybe the V4l list) not too long
> ago.
>   


Yes. That's why I keep trying to find spec information on what a 
"standard" VBI stream looks like.
But I'm not an mpeg/hardware programmer and so far simply asking around 
hasn't turned up anything.


-- 
Jesse Guardiani
Programmer/Sys Admin
jesse at wingnet.net