help='Specify ffmpeg/avconv audio quality, insert a value between 0 (better) and 9 (worse) for VBR or a specific bitrate like 128K (default %default)')
postproc.add_option(
'--remux-video',
metavar='FORMAT',dest='remuxvideo',default=None,
help='Remux the video to another container format if necessary (currently supported: mp4|mkv, target container format must support video / audio encoding, remuxing may fail)')