gstreamer: enable webrtc plugin by default

[razvanphp]

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This PR enables gstreamer webrtc plugin by default.

Motivation

Since 2021 webrtc is recommended by W3C for web real-time communication, assigning multiple IETF standards for the same purpose. This plugin is a part of the GStreamer project since early 2018, when webrtcbin was merged and become part of the GStreamer 1.14 release. Since then, the team at Centricular has been working on improving the plugin and adding new features. This plugin is now considered stable and is used by many projects, including popular open-source WebRTC servers.

Issues

I've read this comment from another attempt, but I think I solved it easier, since libnice compiles without gstreamer dependancy.

Tests

I've compiled both gstreamer and libnice locally and tested with brew test & a local app I have developed in python, all is working well and gstreamer finds the necessary plugins (webrtcbin, libnice) on it's own from the brew plugins folder, using the latest version of libnice (which is good).

References

• https://webrtchacks.com/webrtc-plumbing-with-gstreamer/
• gst-plugins-bad missing webrtcbin plugin #25649
• "brew reinstall --build-from-source gst-plugins-bad" lands on error #151373 (comment)
• Added required dependencies for WebRTC and SRT elements #25680
• gstreamer: add linbice dependency #161361
• gstreamer 1.24.8 + break circular dependency between gstreamer and libnice #171902
• gstreamer: use monorepo build #125996 (comment)

CC @aconchillo @carlocab @ystreet

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[carlocab]

Thanks, but this approach doesn't work either.

I think you'll need to make the approach at #171902 work instead.

[razvanphp]

Thanks, but this approach doesn't work either.

I think you'll need to make the approach at #171902 work instead.

Thank you for the quick review!

Unfortunately my limited knowledge in meson builds probably makes me the wrong guy for the task, but looking forward for the gstreamer to hop-in hopefully. @nirbheek maybe?

Cheers,
R

[nirbheek]

Unfortunately my limited knowledge in meson builds probably makes me the wrong guy for the task, but looking forward for the gstreamer to hop-in hopefully. @nirbheek maybe?

Unfortunately I know next-to-nothing about Brew, but I am happy to answer any questions you might have, and help with patches to meson build files in libnice or gstreamer.

[razvanphp]

Ok, great, then let's do this.

We need a way to compile gstreamer either:

1. with using the local libnice if found, otherwise pull the latest libnice source, like it is currently doing
2. have a flag like --use-local-libnice in the compiler

Here it is the build command ussed by brew (with args defined above:

homebrew-core/Formula/g/gstreamer.rb

Line 235 in 84eb14a

system "meson", "setup", "build", *args, *std_meson_args

[nirbheek]

That's what https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6871 is for. Here's what you need to do:

1. Add -Dgstreamer=disabled to libnice.rb
2. Apply that patch to gstreamer.rb
3. Add -Dlibnice-gstreamer-only=true to the options in gstreamer.rb. In this mode, gstreamer will download and build libnice only for the gstreamer plugin, and will use the library libnice from the system.

That's it, this breaks the circular dependency.

[razvanphp]

There is a conflict on meson_options.txt in that MR.

I did the required changes.

To be honest, I hope for a cleaner solution on the gstreamer build side. I think this should be the default, check first if there is a libnice installed already via pkg-config instead of duplicating the build job.

[nirbheek]

I think this should be the default, check first if there is a libnice installed already via pkg-config instead of duplicating the build job.

The gstnice plugin is not a part of the gstreamer source code. It's part of the libnice source code. GStreamer already does what you describe when pulling in libnice for the webrtc library.

[carlocab]

You need to fix the brew style failures. Try running brew style gstreamer libnice with this branch checked out at "$(brew --repo homebrew/core)". Some of them might be fixed automatically with brew style --fix gstreamer libnice.

Also, please split your commits so that each commit only modifies one formula at a time.

3. Add -Dlibnice-gstreamer-only=true to the options in gstreamer.rb. In this mode, gstreamer will download and build libnice only for the gstreamer plugin, and will use the library libnice from the system.

This will break when we start blocking formulae from downloading things at build-time, so it would be good to avoid downloading libnice during a meson invocation. This is a big part of why I took the approach I did in #171902.

[nirbheek]

so it would be good to avoid downloading libnice during a meson invocation

If formulae can specify a fetch step manually, you can just run meson subprojects download libnice (or download the tarball and manually place it into subprojects/packagecache/). During setup, you should pass meson setup -Dwrap-mode=nodownload so that meson doesn't download anything automatically.

[carlocab]

This is done in #171902.

You'll need to

brew update
brew upgrade gstreamer
brew install libnice-gstreamer

to pick up the changes. (You might need to wait 20 minutes or so for the formulae.brew.sh to pick up the update.)