I didn't vendor them, but I did do an eyeball scan of every package in the full tree for my project, primarily to gather their license requirements[1]. (This was surprisingly difficult for something that every project in theory must do to meet licensing requirements!) It amounted to approximately 50 dependencies pulled into the build, to create a single gstreamer plugin. Not a fan.

[1] https://github.com/ValveSoftware/Proton/commit/f21922d970888...