[FFmpeg-devel] [PATCH v2] dvdvideo: add DVD-Video demuxer, powered by libdvdnav and libdvdread

[Marth64]

Thank you, Nicolas. I had tinkered with concat this way in the past as PGCs
are indeed just a bunch of segments mushed together, but I had run into
issues specifically with (1) concerns about forced subtitles that pop up
mid stream and (2) unable to figure out custom IO with it. Since dvdnav is
driving the navigation and reading of the disc, I do not have the luxury of
knowing VOB addresses for a perfect read of the title (without fully
playing back). So I don’t have a list of files and sectors to give concat.
As DVD also has cell commands that drive direction of the stream, this
complicates it further. The structure revealed by dvdread alone is not
enough to properly play back; the dvdnav VM plays a key role. Finally, I
had also worry about oddities when having demuxer->submuxer->subsubdemuxer.

In my approach (using mpeg demux directly) there doesn’t seem to be any
issue with concatenation/handling the gaps, and I am flushing the
subdemuxer when they occur. Just the GENPTS sticks out as being a non-ideal
thing to do.

That said, I will take another look and see if I misunderstood at the time.

Best,

On Wed, Jan 10, 2024 at 04:17 Nicolas George <george at nsup.org> wrote:

> Marth64 (12024-01-10):
> > I will add that I still had to maintain a dependency on GENPTS for the
> > inner MPEG demuxer. This is because dvdnav_get_current_time() does not
> > provide exact stream-level PTS. However, the crashing/hanging is fixed
> (by
> > parsing NAV packets), and the output is produced smoothly. GENPTS fills
> in
> > the blanks.
> >
> > If anyone can think of a better way, please let me know. Right now, it
> > works well.
>
> You could imitate what tools/dvd2concat does internally: use
> libdvdread to get the structure of the DVD but let the concat demuxer
> handle all the actual demuxing work.
>
> Regards,
>
> --
>   Nicolas George
>