[mythtv-users] Solved: CC (and maybe Teletext) to DVD

[Chris Isip]

On Tue, Feb 26, 2008 at 12:36 PM, Anthony Zawacki <azmail at thezawackis.com>
wrote:

> faginbagin wrote:
> >>> Anyway, I have come up with an alternative approach. I've tinkered
> with
> >>> mythburn.py (the 0.20.2 version). One of the things I've done is to
> >>> create chapter marks using the commercial marks mythcommflag stores in
> >>> the database. As a result, you can use your DVD remote's skip buttons
> to
> >>> bypass the commercials. I'm planning to include a patch for anyone
> who's
> >>> interested. I skimmed the latest code in trunk, and I think there's a
> >>> good chance my patch might apply cleanly to the latest mythburn.py
> >
> >> Using this information, shouldn't it be possible to create the dvd in a
> >> way that the default movie would then automatically skip the
> commercials
> >> by arranging the chapter order?  You would still have the commercials
> on
> >> the dvd in unreferenced chapters, but you would still get captions and
> >> the movie would play straight through.
> >
> > That's a thought, although I'm not sure it can be done with dvdauthor.
> > Maybe some other tool?
>
> Unfortunately, I don't have a direct example, but I believe that it is
> possible.  It should be able to be done using the <pre> or <post> tags
> for the <pgc>.
>
> > Another thought I had would be to cut commercials from the "final.mpg"
> > created after the CC based subtitle stream has been added. I don't know
> > if a mythtv utility can do this and preserve the subtitles, but perhaps
> > another tool, combined with a SQL query of the mythtv database to get
> > the commercial marks?
>
> I'm less familiar with how captions work than mpeg files in general.
> However, when I get home tonight, I will experiment with gopchop to see
> if captions survive cutting out commercials with it.  The last time I
> looked at gopchop, it didn't support EDLs (Edit Decision Lists, which is
> essentially the list of commercials to be cut) but that was quite some
> time ago.
>
> > FWIW, the IVTV VBI data stream headers have their own time base, very
> > different from the time base of the video and audio streams. I suspect
> > the tools that demux and remux the video and audio streams aren't using
> > the time stamps in MPEG2 stream headers. At least, they don't look like
> > consistent sources of time stamps. I suspect the tools rely more on
> > frame counts and fps. That's one reason why I think doing commercial
> > cutting using the original recording would be tricky. So far, I've only
> > figured out how to decode the stream headers, not the stream data, so I
> > have no idea where frames begin and end.
>
> My understanding, in a simplistic manner, is that MPEG has a Group Of
> Pictures (GOP) which basically is a frame that is the complete picture,
> and then a series of diffs to this first frame.  So, if you cut on a GOP
> marker, you can cut from there to the next GOP marker losslessly.  But
> how the subtitles are folded into the GOPs, I don't know.  I'm fairly
> confident that some subtitles will survive cutting a recording using
> gopchop.  I'm not confident in what the result will be as I could see
> several different possibilities, worse case the subtitles are not cut,
> and they get further and further off with each subsequent cut in the
> video stream.
>
> Anthony
>
>
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Have you tried ccextractor?  It generates srt text files with time stamps.
Would it be possible to modify the srt file according to a list of cutlist
points? Then use spumux to add the modified srt file to the final video.

Chris
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