I am no expert but aren't movies recorded in 6.1 or 7.1 when they play in local commercial movie theater? If the mix is already done for the theater, then why is it so hard to transfer it to DVD?
Yes, movies in theaters have 7 channels, but they are not in the same arrangement as the home. Cinema's use: Left, Left-center, Center, Right-center, Right, Left Surround-array, Right Surround-array.
The down-mix for home goes like this: Left to left, center to center, right to right, left-center 50/50 to left and center, right-center 50/50 to right and center. Then the surround arrays are mapped to those channels. But often a custom mix is done for home distribution anyway. 7.1 discs have always been remixed. Some are to just perform the same steering that ProLogic IIx would do, but others have some discrete mixing work done. The Nightmare Before Christmas Blu-ray has a very effective 7.1 mix.
