doc: tweaks to core/video/video_ffmpeg.py
doc: tweaks to core/video/video_ffmpeg.py

inclement/kivy,kived/kivy,matham/kivy,jegger/kivy,matham/kivy,matham/kivy,manthansharma/kivy,inclement/kivy,KeyWeeUsr/kivy,autosportlabs/kivy,kived/kivy,akshayaurora/kivy,janssen/kivy,jkankiewicz/kivy,tony/kivy,akshayaurora/kivy,LogicalDash/kivy,bionoid/kivy,manthansharma/kivy,jkankiewicz/kivy,tony/kivy,Cheaterman/kivy,rafalo1333/kivy,Cheaterman/kivy,manthansharma/kivy,kived/kivy,KeyWeeUsr/kivy,rnixx/kivy,jkankiewicz/kivy,KeyWeeUsr/kivy,tony/kivy,bionoid/kivy,autosportlabs/kivy,matham/kivy,kivy/kivy,LogicalDash/kivy,LogicalDash/kivy,rnixx/kivy,janssen/kivy,rafalo1333/kivy,bionoid/kivy,autosportlabs/kivy,janssen/kivy,jkankiewicz/kivy,jegger/kivy,rnixx/kivy,janssen/kivy,Cheaterman/kivy,Cheaterman/kivy,kivy/kivy,manthansharma/kivy,jegger/kivy,bionoid/kivy,LogicalDash/kivy,inclement/kivy,jegger/kivy,KeyWeeUsr/kivy,kivy/kivy,akshayaurora/kivy,rafalo1333/kivy