proper calling of ffmpeg from python.py

# thanks to https://github.com/bapoczos/ArtML/blob/master/fast-style-transfer/transform_video.py
# thanks to Barnabas Poczos and Gene Kogan

import subprocess, shutil
import os, fnmatch

        in_args = [
            'ffmpeg',
            '-i', in_path,
            '%s/frame_%%d.png' % in_dir
        ]

        subprocess.call(" ".join(in_args), shell=True)
    
        files = sorted(os.listdir(in_dir))
        base_names = fnmatch.filter(files, '*.png')
        in_files = [os.path.join(in_dir, x) for x in base_names]
        out_files = [os.path.join(out_dir, x) for x in base_names]
        
        evaluate( ... )
        
        fr = 30
        out_args = [
            'ffmpeg',
            '-i', '%s/frame_%%d.png' % out_dir,
            '-f', 'mp4',
            '-q:v', '0',
            '-vcodec', 'mpeg4',
            '-r', str(fr),
            out
        ]

        subprocess.call(" ".join(out_args), shell=True)
        print('Video at: %s' % out)