You don't fling uncompressed video between apps like that, it goes straight to the hardware-accelerated h.264 (or whatever) encoder and then a low bandwidth stream comes out. Local AF_UNIX sockets (aka userspace dbus) provide ample bandwidth for that use case.
Yes, that's what I was talking about. Current dbus is is using local AF_UNIX sockets for transport -> the current transport is plenty fast enough to push encoded video over.