[FFmpeg-devel] [PATCH] avformat/srtenc: avoid segmentation fault when transcoding from SSA to SRT

[Gilles Chanteperdrix]

On Sat, Mar 07, 2015 at 11:46:44PM +0100, Nicolas George wrote:
> Le septidi 17 ventôse, an CCXXIII, Gilles Chanteperdrix a écrit :
> > You need an ASS file that produces a sub-title frame without text. I
> > have been carrying this patch since 2013, I am afraid I no longer
> > have the problematic file.
> 
> I tried an ASS file with an empty text part, and it did not crash either. It
> is entirely possible the problem has disappeared due to some of the reworks
> of the text subtitles code since you experienced it.
> 
> I am sorry to insist, but I am always suspicious of changes that go "if the
> value is not what we expect, silently ignore it", because they frequently
> should return an error or hide a bug earlier in the code; for these reasons,
> I would like either a more detailed analysis or a chance to see for myself
> before this patch is applied.

If I read ffmpeg current documentation here:

http://www.ffmpeg.org/doxygen/2.5/group__lavc__core.html#ga828218dcb8874ab2c5af8d486c365421

It seems that when a subtitle rect type is SUBTITLE_ASS (which is
the case in the code which my patch modified), there is no guarantee
that the text field contains something.

-- 
					    Gilles.
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