v1.4.1

Fixed

• audio_meta.read_field now returns None for video container files (MP4,
  MKV, MOV, …); previously read_field called mutagen directly without going
  through can_read, so mutagen — which can read MP4 tags — returned audio
  field values (title, duration, …) for video files; {au:…} tokens in a
  replacement template could therefore resolve on video files as if they were
  pure-audio files