[FFmpeg-devel] [PATCH] configure: unmark FDKAAC as nonfree

[Jean-Baptiste Kempf]

On Wed, Feb 19, 2020, at 01:46, rcombs wrote:
> Red Hat legal believes the FDK license to be free when using their stripped
> version (https://github.com/UnitedRPMs/fdk-aac-free/releases), as the patent
> clause is a no-op now that the relevant patents on that version are expired:
> https://bugzilla.redhat.com/show_bug.cgi?id=1501522

Their version removes a large part of the encoder and soo much of the decoder:
https://cgit.freedesktop.org/~wtay/fdk-aac/commit/?h=fedora&id=8dcaebbdb5112d5930b6202a8880f89aeabb3722
to the point that this library is almost unusable:
- a worse decoder than the normal AAC one inside libavcodec. It notably does not even decode SBR! See [1]
- a stripped down encoder that removes sooo much, that noone has any idea of the quality, because never benched.

So, what's the point?

Also, I _really_ doubt that their decoder removed all the patents related to AAC that have not expired, and notably they have no proof for it.
The AAC list of patents is not public https://www.via-corp.com/licensing/aac/ and there are many other patents outside of the main pool. Notably I really doubt the DRC and PS part are un-patented.

So, they have done their own analysis, that they keep private and we should just hope they are right?
Because the argument from the linked page that is "I removed SBR decoder" and that is absolutely not complete. There are wayyy many more patents on AAC, including ones on PS and DRC (IIRC, PS is from 2004 for example, that means patented until 2024).

So, they removed some code and say  "we removed all patents" and we should believe them, without proof and analysis?
(Since when was a MPEG codec without patents???) 

> Plex legal believes that the license is GPL-compatible in general:

Plex is not a trusted legal member of the community for numerous reasons.

> builds linking to it and to GPL code are nonredistributable. The source is
> available under a license widely understood to fulfill some definition of
> "free", and the contention around it largely comes down to a technicality.
> If a user or packager wants to redistribute builds with it at their own risk,

Why even do that?

We have a decoder inside libavcodec that is good and supports a lot of AAC cases, we have an encoder that is not ridiculous, while not the best, but because some RedHat people did a version stripping everything to a point that it does decodes less streams than the normal decoder and an encoder whose quality was never tested, we should drop everything and supports that instead?

(not even discussing the fact you cannot detect which version is "free" and which is "non-free", nor the fact that the legal analysis from Redhat is not public)

So unless there is, an answer from FSF (who never answered to RedHat), a list of all patents from the licensors and the detail explanation from RedHat of what they did exactly to work-around the patents, I would say total no.


Let me suggest something else: remove fdk-aac from the codebase.
Supporting fdk-aac in the codebase just gives incentives from not improving the rare cases where the decoder does not work, or improving the encoder quality, and just is a bait for licensing violations.

Best,

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1501522#c22

-- 
Jean-Baptiste Kempf -  President
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