update Viewer.encode_animation() for current ffmpeg (4.2.4)
update Viewer.encode_animation() for current ffmpeg (4.2.4)

BubuLK/sfepy,rc/sfepy,sfepy/sfepy,rc/sfepy,rc/sfepy,sfepy/sfepy,BubuLK/sfepy,BubuLK/sfepy,vlukes/sfepy,vlukes/sfepy,vlukes/sfepy,sfepy/sfepy