[FFmpeg-devel] [PATCH 1/2] libavformat/mxfenc.c: Fix segfault when writing an audio packet when there has not been a video one.

Marton Balint cus at passwd.hu
Tue Oct 20 16:43:45 CEST 2015

On Mon, 19 Oct 2015, Tomas Härdin wrote:

> On Mon, 2015-10-19 at 11:40 +0200, Alexis Ballier wrote:
>> On Mon, 19 Oct 2015 10:30:00 +0200
>> Michael Niedermayer <michael at niedermayer.cc> wrote:
>>> On Fri, Oct 16, 2015 at 10:42:32AM +0200, Alexis Ballier wrote:
>>>> This happens when writing the trailer of a file containing audio
>>>> but that has not muxed any video packet. Fixes ticket #4817.
>>>> ----
>>> from IRC:
>>> <thardin> maybe it should print a warning that there has been no
>>> video?
>> maybe, but what would be the right condition ? just this case ? or when
>> writing any edit unit without video? or... ?
>> I haven't been able to find clear references on this (well, those smpte
>> specs I googled aren't esp. easy to read either), but e.g. the muxer
>> refuses to mux without exactly one video stream, so maybe, an empty
>> video stream is also an error; I don't know
> I'm not particularly fond of second-guessing these kinds of things. D-10
> is really anal about what constitutes a legal file, so it's probably
> best not to write anything if something seems amiss. In the end, the
> real test for correctness is whether the output works with all gear for
> your particular use case. But segfaults are important to fix, so I'm not
> too concerned here. Plus my main concern is mxfdec, not mxfenc.

Why not simply return error and print an error explaining "An audio packet 
was muxed before a video, this is not supported."

Segfault -> error is much better than segfault -> possibly broken file.


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