The problem there is video: you can only assign one HDMI input per source. For my Blu-ray Audio discs (or concert videos), I need to be able to see video, and there is no way to assign the HDMI input from the Oppo to both Blu-ray and CD.
Set 7.1 to CD input and select CD then hit the option button on the remote hop down to video select and choose the right HDMI source. This is how i have watched tour de france while listening to music. (I used XLR stereo instead of 7.1 though)
Edit: if you have an older marantz remote or logitech harmony or such you can (still i think) stay on the hdmi input and just toggle 7.1 on or off.
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