Use libplacebo with gstreamer as a video sink

Libplacebo has many great options, has good hardware support, has debanding, dithering, scaling, etc. It would be great if we could videosink straight into libplacebo.

In theory, this should be possible by making a custom plugin to send the textures to libmpv or libplacebo. In practice, I have no clue. If you have this working, do reach out?