Select provider of libav* libraries

[Andreas Cadhalpun]

Hi Bálint,

On 05.06.2015 17:25, Bálint Réczey wrote:
> 2015-06-05 0:28 GMT+02:00 Andreas Cadhalpun <andreas.cadhalpun at googlemail.com>:
> ...
>>> That's not only because of optimization, but also for licensing
>>> issues: The lib*-extra-* packages are licensed with GPLv3+, which is
>>> not acceptable for the majority of applications in debian.
>>>
>>> Note that it does not matter whether or not there are GPLv3+
>>> applications in the archive. These -extra- package do provide
>>> additional functionality that users do appreciate. However, we cannot
>>> provide that in the "standard" libav* packages because we do have
>>> GPLv2-only applications that we must not link against a GPLv3
>>> libavcodec.
>>
>> The current implementation of the extra flavor doesn't prevent using it
>> with a GPLv2-only program and thus is effectively nearly as bad as just
>> enabling the GPLv3 code in the standard build.
>> Adding a mechanism to prevent this would make the extra flavor even
>> more complex.
> The aim is not preventing GPLv3 usage, but offering a choice for
> reverse dependencies.

The problem is that using a GPLv2-only program like hedgewars [1] with
the GPLv3+ libavcodec-extra is not legally allowed, but currently
possible, because hedgewars depends on:
 libavcodec56 (>= 6:11~beta1) | libavcodec-extra-56 (>= 6:11.1)

This has been discussed some month ago on the debian-multimedia list [2].

> GPLv2 only packages can build-depend on only the GPLv2 compatible -dev
> packages, while packages compatible with GPLv3 can include FFmpeg's
> GPLv3 -dev packages in the build dependencies as well.

I don't think having different build-dependencies would help, because the
API is the same for GPLv2+ and GPLv3+. The possible solutions discussed
back then were around manually adding binary package dependencies.

> I don't have the numbers on the GPLv2-only packages,

There are a few, at least those mentioned in [3].

> but if there are
> important ones which can't be relicensed this may make a good reason
> for providing separate GPLv2 and GPLv3 compatible libraries.

The thing is that the only additional functionality of the GPLv3+ libavcodec
is an AMR encoder. I think this is not enough to justify the hassle with
the extra variant.

Best regards,
Andreas


1: https://tracker.debian.org/media/packages/h/hedgewars/copyright-0.9.20.5-12
2: https://lists.debian.org/debian-multimedia/2014/11/msg00000.html
3: https://lists.debian.org/debian-multimedia/2014/11/msg00004.html