import os

aac_cmd = 'ffmpeg -i "{file_name}" -c:a aac -b:a 256k aac/{output_name}.aac'
opus_cmd = 'ffmpeg -i "{file_name}" -c:a libopus -b:a 96k ./opus/{output_name}.opus'
mp3_cmd = 'ffmpeg -i "{file_name}" -c:a mp3 -b:a 128k ./mp3/{output_name}.mp3'

for d in ('mp3', 'opus', 'aac'):
    os.mkdir(d)

counter = 1

for f in [x for x in os.listdir() if os.path.isfile(x) if '.flac' in x]:
    os.system(aac_cmd.format(file_name=f, output_name=counter.__str__()))
    os.system(opus_cmd.format(file_name=f, output_name=counter.__str__()))
    os.system(mp3_cmd.format(file_name=f, output_name=counter.__str__()))
    counter += 1