Yes, some options are not yet recognized; this will change in future commits.
Yes, it ain't perfect; don't cry now.
It is a bit different from what's been done before to actually work with
sh.

They still aren't perfectly compliant though...

DBus, XOSD and Audio Scrobbler interfaces depend on this.

Also protect concurrent access to p_sys between main thread and libvlc callbacks

fixes: #4827

aout_FiltersCreatePipeline() deals with it internally.

This reverts vlm callback behaviour before 67b16b1b

It avoids creating/destroying texture uselessly.

It is enabled only on linux/win32 when opengl ES is not used and when
non power of 2 textures are supported.

Only RGBA colorspace is supported for the subpicture.

Not yet used.

It will allow to add subpictures blending.