Obviously this should have been done a while ago... Encoding Formats: Dolby Digital 5.1 - L/C/R + SL/SR + LFE (384 or 448k/s) Dolby Digital 5.1 EX - L/C/R + SL/SR + LFE + matrix Rear Centre dts 5.1 - L/C/R + SL/SR + LFE (768 or 1,536k/s) dts '6.1'* ES-Matrix - L/C/R + SL/SR + LFE + matrix Rear Centre dts 6.1 ES-Discrete - L/C/R + SL/SR + LFE + discrete Rear Centre *obviously they call it "6.1" but it is only 5.1 in reality. Decoding Format: THX EX Surround 7.1 - L/C/R + SL/SR + LFE + two matrix rear centres; depending on the product, the matrix rears can be summed mono or derived stereo. This is applied to Dolby 5.1 EX titles. Later Dolby 5.1 EX was introduced as THX 7.1 was too expensive for the majority of systems. Certifications: THX Ultra2 - update for 7.1 systems, rated for 3,000+ cu.ft rooms THX Ultra - 5.1 systems, rated for 3,000+ cu.ft rooms (same as the old THX cert.) THX Select - 5.1 or 7.1 systems, rated for 2,000+ cu.ft rooms Other THX formats aren't worth anything. Current virtualising formats for two channel: Circle Surround 5.1 ("CS 5.1") - derived centre + SL/SR + LFE Dolby Pro Logic II - derived centre + SL/SR + LFE dts Neo 6 - derived centre + SL/SR + LFE Logic 7 - derived centre + SL/SR + SBL/SBR + LFE can be applied to either stereo or 5.1/6.1 formats depending on sophistication of processor. Limited to Lexicon and Harmon Kardon equipment.