In addition to using more recent libraries, this avoids this dynamic linking error when mixing a GStreamer version from outside the jhbuild in Fedora 28:
(WebKitWebProcess:26878): GStreamer-WARNING **: Failed to load plugin '/home/ntrrgc/Apps/gst-build/build/subprojects/gst-libav/ext/libav/libgstlibav.so': /lib64/libavutil.so.56: undefined symbol: vaExportSurfaceHandle
Created attachment 342279 [details]
Comment on attachment 342279 [details]
Clearing flags on attachment: 342279
Committed r232633: <https://trac.webkit.org/changeset/232633>
All reviewed patches have been landed. Closing bug.