Since allocators keep an available memory queue to reuse, video format and usage
hint are now persistant while allocator's memories are around.
This patch adds _set_format() and _get_format() for both VA allocators.
_set_format() validates if given format can be used or reused. If no allocated
surface previously it creates a dummy one to fetch its offsets and
strides. Updated info is returned to callee.
GstVaPool uses _set_format() at config to verify the allocator capacity and to
get the surfaces offsets and strides, which are going to be used by the video
meta.
Allocator extracted caps are compared with caps from config and if they have
different strides or offsets, force_videometa is set.
A new bufferpool method gst_va_pool_requires_video_meta() is added return the
value of force_videometa. This value is checked in order to know if decoders
need to copy the surface if downstream doesn't announce video meta support.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1667>
New plugin with an element for H.264 decoding with VA-API. This novel
approach, different from gstreamer-vaapi, uses gstcodecs library for
state handling.
The code is expected to looks cleaner because it uses VA-API without
further layers or wrappers.
* It uses the first supported DRM device as default VA display (other
displays will be supported through user's GstContext)
* Requires libva >= 1.6
* No multiview/stereo profiles neither interlaced streams because
gstcodecs doesn't handle them yet
* It is incompatible with gstreamer-vaapi
* Even if memory:VAMemory is exposed, it is not handled yet by any
other element
* Caps templates are generated dynamically querying VAAPI, but YV12
and I420 are added for system memory caps because they seem to be
supported for all the drivers when downloading frames onto main
memory, as they are used by xvimagesink and others, avoiding color
conversion.
* Surfaces aren't bounded to context, so they can grow beyond the DBP
size, allowing smooth reverse playback.
* There isn't yet error handling and recovery.
* 10-bit H.264 streams aren't supported by libva.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1379>
