I think we may be doing some work on multiple decoders at the moment for another product (entirely different context, don't bother guessing!) so I guess we'll find out pretty soon what's possible.

This brings up an old "they'll never actually do it, but it sure would be cool" wishlist item of mine:

It would be cool to have multiple encodings of the same track stored in the empeg where you could then do A/B tests between them to figure out which encoding you prefer. Run the decoders in parallel and flip back and forth seamlessely between them.