Re: [FFmpeg-devel] [PATCH] avcodec/libx265: Don't copy A53 closed captions by default

["Tomas Härdin" <git@haerdin.se>]

tis 2024-06-11 klockan 10:16 +0200 skrev Andreas Rheinhardt:
> Tomas Härdin:
> > tis 2024-06-11 klockan 10:05 +0200 skrev Andreas Rheinhardt:
> > > Tomas Härdin:
> > > > tis 2024-06-11 klockan 09:42 +0200 skrev Andreas Rheinhardt:
> > > > > The SEI handling of libx265 is buggy and can easily lead
> > > > > to memory corruption: It reuses certain buffers, but when
> > > > > reusing them it presumes that it is enough for these buffers
> > > > > to exist and does not check whether they are actually large
> > > > > enough to hold what is intended to be stored in them.*
> > > > > 
> > > > > Our users are exposed to this because forwarding A53 CC data
> > > > > is enabled by default. Change this to make it disabled
> > > > > by default.
> > > > > 
> > > > > "Fixes" tickets #9666, #10411, #11052 and (presumably)
> > > > > #10906.
> > > > 
> > > > Shouldn't users use non-buggy versions of libx26? I've had
> > > > people
> > > > ask
> > > > about CC, and I'm sure many users would be annoyed at them
> > > > suddenly
> > > > breaking. I suggest complaining loudly at compile time and/or
> > > > when
> > > > loading libx265 instead
> > > 
> > > Non-buggy versions of libx265? People use what they have because
> > > it
> > > exists.
> > 
> > What I'm getting at is that this is libx265's responsibility, and
> > the
> > responsibility of packagers not to ship broken versions of it. Does
> > all
> > A53 CCs break with the present libx265 bug or only some?
> > 
> 
> 1. There is no version of libx265 with this bug fixed (the bug itself
> is
> here:
> https://bitbucket.org/multicoreware/x265_git/src/8787e87020d77416f0ff0b7f3c97ac8b90332c31/source/encoder/encoder.cpp#lines-1086:1117
> )

Then I expect libx265 to fix it posthaste and push a new release, and
for Debian etc to discourage installing versions prior to that as
appropriate

We can change the default of course (yolo!), but expect non-zero
numbers of angry users whose workflows suddenly break

/Tomas
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