[FFmpeg-devel] [PATCH 4/4] matroska: fix IGNIDX handling

[wm4]

On Thu, 12 Feb 2015 14:25:41 +0100
Michael Niedermayer <michaelni at gmx.at> wrote:

> On Mon, Feb 09, 2015 at 08:39:01PM +0100, wm4 wrote:
> > Just because the user requested the seek index to be ignored, we can't
> > just skip essential headers. At least tags are often located at the end
> > of the file, and the old code simply ignored the seekhead for all
> > elements, not just the cue index. Also, it looks like it used the index
> > even if IGNIDX was set if the cue index was located in the beginning of
> > the file.
> > ---
> >  libavformat/matroskadec.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> do you have a testcase / sample for this ?
> 
> [...]
> 

No. A file triggering this case would have to have a SeekHead at the
end of the file, which points to a tag element also located at the end
of the file. In this case, IGNIDX without this patch applied would skip
tags. This can even happen that can absolutely required element like the
track list. So I'd say this is required for correctness.