[Libva] Add passthrough mode to upload/download elements

[Gwenole Beauchesne]

Hi,

2012/9/6 Simon Farnsworth <simon.farnsworth at onelan.co.uk>:

> The easy fix was to make vaapiupload capable of passthrough, so that I can
> unconditionally set my playbin2 video-sink as "vaapiupload ! vaapipostproc !
> vaapisink" and let vaapiupload enter passthrough mode when playbin2 chooses
> vaapidecode as the decoder.

That looks reasonable for 0.3.x branch. For master, the longer term
solution is to allow video/x-raw-yuv surfaces from vaapisink. Halley
has a patch for it. My preference will be to have a common object that
would be used in there but also in vaapiupload element, in the interim
solution.

> I also made the corresponding changes to vaapidownload; I don't personally
> need them, as I only use vaapidownload when debugging, but the changes
> aren't complex.

I don't really see where this would actually be useful either. Chances
are that we end up to only keep vaapidecode and vaapisink elements
once we merge the port to GStreamer 1.0 API.

Regards,
Gwenole.