Is it possible to get the non downmixed AC3 signal from the optical out and the downmixed MPEG or AC3 signal from HDMI at the same time?

I got a answer on a different forum that this is not possible.
Can a Developer please explain if this is a hardware or software limitation?

So to explain my problem.
My setup is DM8000 hdmi to sammy tv and can only handle 2ch on hdmi else there is no sound.
DM8000 optical to 5.1 receiver.
I only use the receiver when watching movies with 5.1 sound and for 2ch regular watching the tv speakers is a better option at least for me.
To switch between downmix on/off is so annoying.

cheers!