BD players are required to support Dolby Digital and DTS, and linear PCM (up to 7.1 channels.) The BD standard has optional support for Dolby Digital Plus and the lossless formats Dolby TrueHD and DTS HD (which means many players will NOT have these facilities) HD DVD players are required to ALL of the above audio codecs. Analogue will support every codec that the player supports as will HDMI 1.1 if the player has the audio codec like all HD DVD players (but not like all BD who are pushing HDMI 1.3 as their 'solution'). The HD DVD players currently encode every format to HQ DTS which means a HQ legacy connection is also possible. This is a great feature.