All the pieces aren't there: extraction exists, variable mixing does not. You're looking at the electronic equivalent of a Y-splitter (when centre speaker is set to 'none') and considering that a mixer. It's not.

Oh, for Pete's sake! If one can code C' = xC, L' = (1-x)C/2+L, R'=(1-x)C/2+R, for x either 0 or 1, one can code if for x between 0 and 1. DSPs and hybrid processors do pretty good fixed and floating point math these days (likely necessary for DD decoding anyway).

The only assumptions I make are that (a) the 990 does decoding and processing in the digital domain, (b) it has fixed and/or floating point capabilities, and (c) it can combine data from independent channels.

What part of the linear algebra are you having trouble with?

You called them "hidden" and "crippled" (instead of 'secret' and 'disabled', respectively).

Yes, because I believe they exist in code that any reasonable programmer would refactor in such an application, but are not exposed to the end user. 'secret' is your word to imply a conspiracy, not mine. I do not believe the lack of access to this funcionality was intended to thwart experimentation, but rather to protect the unsophisticated end user from themselves -- I see no malice in the restriction.

Early adopters? The surround processing technology in the 990 is mature; nothing there on the bleeding edge (even PLIIx has been around for almost two years).

I was referring to the practice of plunking down over a thousand dollars for a product over the internet, sight unseen, on the reputation of the seller.

In any case, as tempting as it is to have "feature and bug fix prototyping for free", I'm glad that consumer electronic companies don't design their products to accomodate hackers.

Actually, increasingly, companies do this.

Outlaw can by offering a test mode which provides greater control capabilities over the unit via it's serial port. This is useful for automated testing in the factory. It would also be useful for hackers.

Note that others can set their centre speakers to 'none'

And I've asked for a description of how (starting from a reset unit). I can't, and no one has responded. I do not believe that the firmware in my unit is somehow different from stock -- that's your conspiracy theory. (It would be nice if there was a way to obtain the firmware version from the unit). Either I'm doing something wrong, or there is a "trick" to specifying two small L+R speakers and a sub.