[mythtv-users] VBI subtitles with ivtv cards?

Mark Cooke mpc at jts.homeip.net
Fri Sep 23 20:54:48 UTC 2005


On Fri, 2005-09-23 at 16:16 -0400, Jesse Guardiani wrote:
> Mark Cooke wrote:
> > 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

It was in late august, after picking up the original header-length
mismatch for the 2-packing bytes.  Not sure the exact version, but it
was definitely no later than 0.3.7j (current version on my backend)

Sounds like it is worth trying the newer version with VBI again. 

> [...]
> 
> > 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.

Well, the specs for this are all freely available...

ESTI Docs (register with just an email address for as many downloads of
ESTI specs as you want.  They've sent me 1 email invite to a conference
since I registered 6 weeks ago, so it's not a major spam-source):

EN 300 294 : TV WSS 625-line (PAL) spec. (v 1.4.1)
EN 300 429 : DVB framing structure/coding/modulation
EN 300 468 : Service Information spec (1.6.1)
EN 300 472 : ITU-R Teletext in DVB bitstreams (1.3.1)
EN 300 706 : Enhanced Teletext spec (1.2.1)
EN 301 775 : VBI information in DVB bitstreams (1.1.1)
             (WSS / CC / teletext / vps )

TR 101 211 : SI guidelines  (1.6.1)
TS 101 154 : Implementation guidelines (1.7.1)
TS 101 197 : Head-end architecture (1.2.1)

The 472 and 775 specs are the most handy for the VBI stuff, but I
haven't had sufficient time to read them in enough detail to hack up
ivtv-vbi.c to do 'standards-based' encoding.


Googling around should find you PDFs of recent drafts or better of
ISO/IEC 13818-1, which defines transport, program, PES streams, etc.


HTH,


Mark



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