a bit later ... but at least it gives a starting point for people
wanting to have fun with transcode / audio / filter chains)

less than that of the planar version (uses nearest neighboor instead of
interpolated colors)

Fixes a bunch of crashes at exit.

It needs to be done by the parent (VLM or playlist)

vlc_threadobj() is no use otherwise. People may want not to enable
reference checking all the time also...

with an ugly green in packed YUV).

Ugly hack to make the filter chain work correctly for the video output core. This will be removed once all the different picture release methods have been merged into one coherent method.