spice, dmabuf, egl and streaming

[Frediano Ziglio]

Hi,
  I'm a member of spice team (http://www.spice-space.org/) in RedHat.
We are using GStreamer to handle streaming of video remotely using different
compression coders (H264, MJPEG, VP8).

We are facing a new challenge, streaming frames from 3d card!
Of course we want it faster as possible. Some graphics cards implements
compression so we would like to use this feature if present and potentially
not extracting the texture from the graphics card. This is not always possible
(libraries not installed, not supported by card, etc) so we need also a fallback.
Potentially we can start with an EGL texture which can be easily converted to
a dmabuf if needed. Note however that not all dmabuf supports mmap which seems
the way gst_dmabuf_allocator_new allocator works so potentially EGL texture is
better.
There is a current experimental patch which is using gstreamer vaapi library
but extract the raw image from the texture. Looking at vaapi seems that you
can convert a dmabuf to a VASurfaceID to avoid the memory copy but seems
not used by gstreamer vaapi. I saw there is a gst_vaapi_surface_new_from_egl_image
but I don't understand how to make the code call it.

Frediano