def extract_all(videodir,save_dir):
filenames = os.listdir(videodir)
for file in filenames:
if 'mp4' in file:
savedir = os.path.join(save_dir,file.replace('.mp4',''))
if not os.path.isdir(savedir):
os.makedirs(savedir)
shell_cmd= \
"ffmpeg -i {} -vf select='eq(pict_type\,I)' -vsync 2 -f image2 {}/frame_%02d.jpg".format(videodir+'/'+file,savedir)
os.system(shell_cmd)