meson: add 'gpl' option and only build plugins with (A)GPL deps if explicitly enabled

Require explicit opt-in to build plugins with (A)GPL dependencies.

Keep ugly/bad options on 'auto' for now so cerbero doesn't fail.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1084>

1 files changed, 24 insertions, 0 deletions

diff --git a/README.md b/README.md
index 270c570f0e..591f3f3abc 100644
--- a/README.md
+++ b/README.md
@@ -129,6 +129,30 @@ the build files to find `libmfx`.
 The plugin will be automatically enabled if possible, but you can ensure it by
 passing `-Dbad=enabled -Dgst-plugins-bad:msdk=enabled` to `meson`.
 
+### Building plugins with (A)GPL-licensed dependencies
+
+Some plugins have GPL- or AGPL-licensed dependencies and will only be built
+if you have explicitly opted in to allow (A)GPL-licensed dependencies by
+passing `-Dgpl=enabled` to Meson.
+
+List of plugins with (A)GPL-licensed dependencies (non-exhaustive) in gst-plugins-bad:
+ - dts (DTS audio decoder plugin)
+ - faad (Free AAC audio decoder plugin)
+ - iqa (Image quality assessment plugin based on dssim-c)
+ - mpeg2enc (MPEG-2 video encoder plugin)
+ - mplex (audio/video multiplexer plugin)
+ - ofa (Open Fingerprint Architecture library plugin)
+ - resindvd (Resin DVD playback plugin)
+ - x265 (HEVC/H.265 video encoder plugin)
+
+List of plugins with (A)GPL-licensed dependencies (non-exhaustive) in gst-plugins-ugly:
+ - a52dec (Dolby Digital (AC-3) audio decoder plugin)
+ - cdio (CD audio source plugin based on libcdio)
+ - dvdread (DVD video source plugin based on libdvdread)
+ - mpeg2dec (MPEG-2 video decoder plugin based on libmpeg2)
+ - sidplay (Commodore 64 audio decoder plugin based on libsidplay)
+ - x264 (H.264 video encoder plugin based on libx264)
+
 ### Static build
 
 Since *1.18.0* when doing a static build using `--default-library=static`, a