[FFmpeg-devel] FFmpeg 5.0

[Neal Gompa]

On Sun, Oct 30, 2022 at 4:10 PM Michael Niedermayer
<michael at niedermayer.cc> wrote:
>
> On Sat, Oct 29, 2022 at 02:29:56PM -0400, Neal Gompa wrote:
> > On Fri, Oct 28, 2022 at 2:23 PM Michael Niedermayer
> > <michael at niedermayer.cc> wrote:
> > >
> > > Hi
> > >
> > > According to our
> > > https://trac.ffmpeg.org/wiki/Downstreams
> > >
> > > Noone and nothing is using 5.0
> > > should i make another release of 5.0 ?
> > > should i move 5.0 to olddownloads ?
> > >
> > > does anyone use it ? plan to use it or know of someone using it ?
> > >
> >
> > Fedora 36 still uses FFmpeg 5.0 as I discovered there was an ABI break
> > that made upgrading to FFmpeg 5.1 not possible for F36. FFmpeg 5.1 is
> > used for Fedora 37, though.
> >
> > This had apparently been also discovered by openSUSE some time ago:
> > https://build.opensuse.org/package/view_file/multimedia:libs/ffmpeg-5/work-around-abi-break.patch?expand=1
>
> You can replace 5.0 by 5.1 but not 5.1 by 5.0, The compatibility is only
> in one way.
> Iam assuming here you talk about the addition of functions and there is
> not some other issue iam not aware of.
>

My understanding is that when using symbol versions, modifying the
symbol table creates a breakage on its own.

>
> >
> > Fedora 36 will still be supported until June, so I would appreciate it
> > if another release of 5.0 would be made.
>
> I have to admit i feel a bit undecided. Id like to first understand why
> this situation/"need" exists for fedora but not others
>
>

I mostly did this at the advice of Jan from openSUSE and the RPM
Fusion ffmpeg maintainers.

> >
> > Do we have ABI testing in place for submitted patches? I haven't seen
> > any evidence of CI testing of patches submitted to the mailing list,
> > but maybe I'm looking in the wrong place? If there is, maybe we can
> > consider adding some kind of ABI testing for release branches, using
> > tools like libabigail[1] with abidiff[2]?
> >
> > [1]: https://sourceware.org/libabigail/
> > [2]: https://www.mankier.com/1/abidiff
>
> iam not sure there is agreement between you and others of what is a ABI break
> so the tool maybe will not help.
>
> I have generaly done testing with replacing old libraries by new when doing
> releases. But for me a ABI break is if replacing a library by another breaks
> some binary that is not rebuild and linked to the new lib.
>
> More testing is always good and welcome of course.
>

Yeah, I think that qualifying how ABI is validated in a reproducible
way would be useful. The abigail tooling can help here, In Fedora,
every update runs through abigail validation too. I vaguely recall
that it warned me when I did the update in Rawhide, which is how I wound
up talking to Jan in openSUSE and RPM Fusion maintainers, who both
didn't refresh FFmpeg on stable branches with 5.0 to 5.1.

It's also entirely possible that I was *too* cautious, and I'm okay
with having a conversation that leads me to do differently in the future.





--
真実はいつも一つ！/ Always, there's only one truth!