In addition to the HD audio soundtracks, many Blu-Ray titles also offer additional audio content in the form of secondary audio, which may include directors' commentaries for example. The secondary audio tracks are usually not encoded in HD but rather in standard Dolby Digital or DTS. Most Blu-Ray players will have a menu option in their setup menu to either enable or disable secondary audio playback. The tradeoff is that when secondary audio is ENABLED, most blu-ray players will not output the HD audio bitstream from discs but instead will play the standard non-HD audio instead. So, to ensure you are getting the full HD audio content from the disc check the setup menu of the Blu-Ray player and ensure the secondary audio option is disabled.