whats the difference between Dolby Digital 5.1 and Dolby Digital Surround?

("Dolby Digital Surround - 4.1") LEFT, RIGHT, CENTER, REARS and SUB only

Now the ones we know and love...These actually give us 6 channels of TRULY DISCRETE audio...(before "5.1" the REAR speakers were in MONO...both made identacle sounds):

("Dolby Digital 5.0") LEFT, RIGHT, CENTER, LEFT REAR and RIGHT REAR only

("Dolby Digital 5.1") LEFT, RIGHT, CENTER, LEFT REAR, RIGHT REAR and SUB-WOOFER only

And thanks to George Lucas, we now have "6.1"...It adds a speaker (or 2) behind us and between our EXISTING rear channels...For "Dolby", they can't fit ANY more channels on their movies...So they found a way to "pack" more info into they REAR channels of "5.1"...The end result of "6.1"is not that different from "5.1":

("Dolby Digital 5.1EX") LEFT, RIGHT, CENTER, LEFT REAR, LEFT RIGHT, CENTER REAR [sort of] and SUB only

Now "DTS" has their very OWN version of "6.1" and it actually fits an EXTRA channel of sound on the disc...The CENTER REAR channel is overly compressed and sounds like a really bad MP3 or digital answering machine...They have a "discrete 6.1" version AND a "5.1" version with more info "packed" into the REAR channels (just like "Dolby")

("DTS 5.1ES") - LEFT, RIGHT, CENTER, LEFT REAR, RIGHT REAR, CENTER REAR [sort of] and SUB only

("DTS 6.1 ES DISCRETE") - LEFT, RIGHT, CENTER, LEFT REAR, RIGHT REAR, CENTER REAR [for real this time] and SUB only