Cannot ouput audio.wav for some .mp4 files

[jlian2]

[jlian2]

I think there may be some problems in this: command = ("ffmpeg -y -i %s -qscale:v 2 -async 1 -r 25 %s" % (opt.videofile,os.path.join(opt.avi_dir,opt.reference,'video.avi'))) output = subprocess.call(command, shell=True, stdout=None)