Don't re-upload VA subpicture if only the render rectangle changed.
Rather deassociate the subpicture and re-associate it with the new
render rectangle.
A GstVideoOverlayRectangle is created whenever the underlying pixels data
change. However, when global-alpha is supported, it is possible to re-use
the same GstVideoOverlayRectangle but with a change to the global-alpha
value. This process causes a change of sequence number, so we can no longer
check for that.
Still, if sequence numbers did not change, then there was no change in
global-alpha either. So, we need a way to compare the underlying GstBuffer
pointers. There is no API to retrieve the original pixels buffer from
a GstVideoOverlayRectangle. So, we use the following heuristics:
1. Use gst_video_overlay_rectangle_get_pixels_unscaled_argb() with the same
format flags from which the GstVideoOverlayRectangle was created. This
will work if there was no prior consumer of the GstVideoOverlayRectangle
with alternate (non-"native") format flags.
2. In overlay_rectangle_has_changed_pixels(), we have to use the same
gst_video_overlay_rectangle_get_pixels_unscaled_argb() function but
with flags that match the subpicture. This is needed to cope with
platforms that don't support global-alpha in HW, so the gst-video
layer takes care of that and fixes this up with a possibly new
GstBuffer, and hence pixels data (or) in-place by caching the current
global-alpha value applied. So we have to determine the rectangle
was previously used, based on what previous flags were used to
retrieve the ARGB pixels buffer.
We previously assumed that an overlay composition changed if the number
of overlay rectangles in there actually changed, or that the rectangle
was updated, and thus its seqnum was also updated.
Now, we can cope with cases where the GstVideoOverlayComposition grew
by one or a few more overlay rectangles, and the initial overlay rectangles
are kept as is.
Create the GPtrArray once in the _init() function and destroy it only
in the _finalize() function. Then use overlay_clear() to remove all
subpicture associations for intermediate updates, don't recreate the
GPtrArray.
Make GstVaapiOverlayRectangle a reference counted object. Also make
sure that overlay_rectangle_new() actually creates and associates the
VA subpicture.
Make it possible to specify the maximum number of references to use within
a single VA context. This helps reducing GPU memory allocations to the useful
number of references to be used.
This is a preferred thread-safe version. Also add an inline version of
g_clear_object() if compiling with glib < 2.28.
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
