[AUDIO_TS]子目錄主要是製作DVD-Audio才會用到；
在DVD-Video規範當中是為了相容性才會存在，
不過都是空的子目錄。

摘錄自Sonic Scenarist Glossary：
AUDIO_TS File directory on a DVD disc (or in a DVD Volume folder) where DVD-Audio data is stored. In a DVD-Video disc, this directory is always empty, though the DVD specification requires that it exist.