Many DVD-A disc has DVD-Video portion that contains the DD 5.1 or DTS 5.1 version of the music in DVD-A area. Your DVD-Video player can play those DD 5.1 or DTS 5.1 tracks if any. But the quality of DD 5.1 is quite inferior to that of the DVD-A tracks and DTS 5.1 track should be be between DD 5.1 and DVD-A in terms of sound quality.