[DVDnav-discuss] [PATCH] handle duplicate language units and pgc's more gracefully

[Fabian Keil]

John Stebbins <stebbins at jetheaddev.com> wrote:

> On 12/28/2012 04:15 AM, Fabian Keil wrote:
> > John Stebbins <stebbins at jetheaddev.com> wrote:
> >
> >> On 11/04/2012 06:33 PM, Fabian Keil wrote:
> >>> John Stebbins <stebbins at jetheaddev.com> wrote:

> >>>> What disc does it crash on?  HandBrake does not use
> >>>> dvdnav_describe_title_chapters(), so this is a code path we have not
> >>>> tested well enough it sounds like.  dvdbackup uses this?
> >>> dvdbackup doesn't use dvdnav_describe_title_chapters() either.
> >>>
> >>> I failed to mention that the crashing application is vlc.
> >>>
> >>> The DVD is a rip of Monty Python season 3 DVD 1 where unreadable
> >>> sector regions have been padded with surrounding sectors using a
> >>> flawed padding strategy, which probably made the "copy" even less
> >>> standard-compliant than the original.
> >>>
> >>> Given the content, it seems very appropriate that the attached patch,
> >>> which prevents this and other crashes, is somewhat silly ...
> >>>
> >>> I made the skip conditions up while going through backtraces until
> >>> vlc stopped crashing. I haven't properly tested yet how they affect
> >>> other DVDs.
> > I haven't noticed any problems with the patches so far.
> >
> > I recently had to use another patch (attached) for "Ghost Protocol",
> > but I haven't verified that the problem actually was due to the pgc
> > deduplication.

> This error is not due to the pgc deduplication.  It is caused by an invalid cell_playback_offset value on the disc. 
> libdvdread does not allocate a cell_playback in this case and applications must check that the value is not null.

Do you count libdvdnav as application here, or is vlc really expected
to check for this (and all the other things libdvdread might not allocate)
before calling dvdnav_describe_title_chapters()?

Fabian
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