Allow plain gst_buffer_map() interface to work with gstreamer-vaapi
video buffers, i.e. expose the underlying GstVaapiSurfaceProxy to the
caller. This is the only sensible enough thing to do in this mode as
the underlying surface pixels need to be extracted through an explicit
call to the gst_video_frame_map() function instead.
A possible use-case of this is to implement a "handoff" signal handler
to fakesink or identity element for further processing.
Implement GstVideoMeta::{,un}map() to support raw YUV buffer upload when
the last component is unmapped. Downloads are not supported yet. The aim
was to first support SW decoding + HW accelerated rendering (vaapisink).
e.g. for Wayland.
Add initial support for GstVaapiVideoMemory backed buffer pool. The memory
object currently holds a reference to GstVaapiVideoMeta.
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
