Enable DMABuf mem at both sink and src pad for vaapipostproc caps which helps to apply DMABuf for more generic use cases: such as "! vaapih264dec ! video/x-raw(memory:DMABuf) ! vaapipostproc ! video/x-raw (memory:DMABuf) ! vaapih265enc" . Or other mem converions like from DMABuf to VASurface through vaapipostproc. This patch is a portion from Junyan.He@intel.com https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi/-/merge_requests/393 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1287>