[fdk-aac] make patent-encumbered HE-AAC optional

[Be-ing]

By default, use a fork of fdk-aac (which was originally written
by Fraunhofer for the Android Open Source Project) which has
support for the patent-encumbered HE-AAC, HE-AACv2, and xHE-AAC
profiles removed. This fork is used by Fedora and Arch Linux to
provide support for most AAC use cases without patent licensing
fees and to permit combining it with GPL software. The upstream
fdk-aac with support for all AAC profiles can be built with the
new 'he-aac' option for this port.

Fedora Legal's opinion, from
https://bugzilla.redhat.com/show_bug.cgi?id=1501522#c112 :
The Fedora Project is aware that the Free Software Foundation
has stated that the Fraunhofer FDK AAC license is GPL
incompatible, specifically, because of Clause 3.

We believe that the fdk-aac software codec implementation that we
wish to include in Fedora is no longer encumbered by AAC patents.
This fact means that Clause 3 in the FDK AAC license is a "no op",
or to put it plainly, if no patents are in play, there are no
patent licenses to disclaim. For this (and only this) specific
implementation of fdk-aac, we believe that the FDK AAC license is
GPL compatible.

[Be-ing]

I have opened a merge request to add CMake support to the fork without HE-AAC. This allowed removing the modified CMakeLists.txt and related files from this port. Also, I merged updates from upstream into the fork without HE-AAC, so now this port will build the same code with or without the he-aac option, except of course for the HE-AAC support.

[Be-ing]

I have asked upstream to tag a new release. Let's wait a bit for them to respond before merging this.

[Be-ing]

@Sibras I am wondering if this PR might present issues building ffmpeg with the fdk-aac option. Should that build fdk-aac with the new he-aac option introduced in this PR?

[Sibras]

@Sibras I am wondering if this PR might present issues building ffmpeg with the fdk-aac option. Should that build fdk-aac with the new he-aac option introduced in this PR?

Yes this may cause some issues. Since this PR changes the default behavior of fdk perhaps make the he-aac option default to on (so optionally disable) to keep that libs functionality consistent.

Also the ffmpeg project doesn't recognize the removal of HE-AAC parts as making it GPL compatible so no matter if its included or not ffmpeg with fdk still requires the non-redistributable license.

[Be-ing]

ffmpeg is the only port in vcpkg that depends on fdk-aac, so I think it would be sufficient to change the ffmpeg port to depend on fdk-aac[he-aac] instead of just fdk-aac for ffmpeg's fdk-aac option.

[Be-ing]

perhaps make the he-aac option default to on

Let's default to not putting users in a questionable legal situation.

[Be-ing]

From https://bugzilla.redhat.com/show_bug.cgi?id=1501522#c29 :

Christian, supporting HE-AAC encoding is the raison d'être of fdk-aac. Otherwise FFmpeg's aac codec is good enough for all other use cases. We already have gstreamer1-libav in RPMFusion covering these, so having a crippled fdk-aac in Fedora is no gain. See https://trac.ffmpeg.org/wiki/Encode/AAC for more information. Unless we're looking at several years until unstripped fdk-aac can be included in Fedora, I think it's not worth the effort to add support for this stripped version to FFmpeg and other multimedia software and we should just wait.

So there wouldn't be much of a point to building ffmpeg with fdk-aac using the fdk-aac fork without HE-AAC. That would be redundant with the AAC codec FFMPEG already has. In Mixxx we have already implemented encoding using fdk-aac, so we'll be using the fork without HE-AAC in our Windows and macOS packages. (If we were starting code for AAC encoding now, I'd suggest using FFMPEG instead, but nevertheless we currently have fdk-aac support implemented.)

[Be-ing]

Rebased on #18549.

[github-actions]

This is a new experimental fast check for PR issues. Please let us know if this bot is helpful!

After committing all other changes, the version database must be updated

git add -u && git commit
git checkout 261c458af6e3eed5d099144aff95d2b5035f656b -- versions
./vcpkg x-add-version --all

Diff

diff --git a/versions/f-/fdk-aac.json b/versions/f-/fdk-aac.json
index d7aee95..941d525 100644
--- a/versions/f-/fdk-aac.json
+++ b/versions/f-/fdk-aac.json
@@ -1,7 +1,7 @@
 {
   "versions": [
     {
-      "git-tree": "b217056128a666ddab48cf0bd9d78098987aaa39",
+      "git-tree": "7c806b3497f78ee26a48f9aa1716afd3198e2021",
       "version-semver": "2.0.2",
       "port-version": 1
     },

[NancyLi1013]

Have you tested the feature he-aac on your local? @Be-ing

[Be-ing]

Yes, this port works both with and without the he-aac feature. And the ffmpeg port works with its fdk-aac feature.

[github-actions]

This is a new experimental fast check for PR issues. Please let us know if this bot is helpful!

After committing all other changes, the version database must be updated

git add -u && git commit
git checkout a863c84812089836a3c0f2f215ab3e2579fc8acf -- versions
./vcpkg x-add-version --all

Diff

diff --git a/versions/f-/fdk-aac.json b/versions/f-/fdk-aac.json
index beccee5..d874a00 100644
--- a/versions/f-/fdk-aac.json
+++ b/versions/f-/fdk-aac.json
@@ -1,7 +1,7 @@
 {
   "versions": [
     {
-      "git-tree": "f218c0d4301af1cb8348d75a8c5b2caabad4b20b",
+      "git-tree": "1ee90ec9cebb3eebb36f0a81a2415f0121c7a8da",
       "version-semver": "2.0.2",
       "port-version": 1
     },

[Be-ing]

Merge?

[NancyLi1013]

Waiting for merge now. @Be-ing

[BillyONeal]

Suggested change

	"description": "A standalone Third-Party Modified Version of the Fraunhofer FDK AAC Codec Library for Android. Uses a fork without HE-AAC, HE-AACv2, or xHE-AAC support to avoid patent licensing and GPL compatibility issues when built without the he-aac option.",
	"description": "The Fraunhofer FDK AAC Codec Library. By default, uses a fork without HE-AAC, HE-AACv2, or xHE-AAC support to avoid patent licensing and GPL compatibility issues. For the original, un-forked version, use the \"he-aac\" feature.",

[Be-ing]

This is required by the license: https://gitlab.freedesktop.org/wtaymans/fdk-aac-stripped/-/blob/stripped4/NOTICE#L54

[BillyONeal]

Hmmmm.... the "for Android" part is the really unfortunate part. I do want this to say something to the effect of "by default uses the fork" rather than always saying it uses the fork.

[Be-ing]

I thought that was clear already but if you have a suggestion for better wording please share.

[BillyONeal]

I'm a bit concerned about changing what we consider an authoritative source for an already shipping port; under normal circumstances we would require adding a new port (for example, fdk-aac-stripped) instead. However, because this is supposedly the same library with a feature removed, it might be OK. How often does upstream fdk-aac change and are you going to be on the hook to apply such changes in a timely manner?

[ras0219-msft]

It looks like this is at least supported by the fedora project: https://src.fedoraproject.org/rpms/fdk-aac-free

[BillyONeal]

It looks like this is at least supported by the fedora project: https://src.fedoraproject.org/rpms/fdk-aac-free

@Be-ing Can you confirm that this is expected to be "supported" tracking upstream closely and apply my suggested change to the description? (I tried to apply that for you but this PR was created without the "allow maintainers to make edits" option checked) Then we'll merge.

[Be-ing]

Yes, this will be maintained. Alpine Linux is considering to package the fork too. Now that I fixed the merge conflicts and CMake build in the fork, maintaining the fork should be a simple matter of merging upstream when there is a release.

[BillyONeal]

Thanks for your contribution!