video_output: fix viewpoint initialization from input
video_output: fix viewpoint initialization from input

Partially revert commits 8a62e7a2e14d8715e9783c895661a3901a2b96bf
and 2d32661b145718b2d31dbf9a2f23b7f7af39799c

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc