Switch between AC3 and stereo

[Johan]

I have my HTPC connected to two different TV sets.
One in my living room and one in my bedroom. In the living room I have a receiver and I want AC3 stream if present. In my bedroom I have a normal TV which can not decode AC3 and here I want normal stereo. My Idea was to have ffdshow audio to decode AC3 to stereo and Intervideo codec to pass through the AC3 to S/PDIF. I want to do this by changing the used audio codec in settings/my movies.

The problem is if I enable AC3 in ffdshow it does not matter if I choose Intervideo or ffdshow codec in MP settings, ffdshow always take control.

Is there any way I can get MP to actually choose the codec I want to use and not let windows decide which is prefered?

Another solution would be to with a simple key press or key combination (which I program in my remote) to switch the ffdshow ac3 between s/pdif or decode library (then I only use ffdshow but changes its internal settings)

Any help appreciated!