The app I'm considering opens a video_processor on its own, with
a NV12 format on input and a ARGB32 format on output.

Tested on Windows: the samples are flipped vertically. While Wine
keeps them untouched.

So added a videoflip in the video processor to be activated when needed.
Signed-off-by: Eric Pouech <epouech@codeweavers.com>