You could perhaps mean seveal things with this question so I'm not quite sure how to answer it accurately. But if you simply wish to connect the videosignal and audiosignal separately then that is indeed possible with the Pioneer BDP-LX55. You can read about it in the user manual.
I've tested this player at home and it's very simple to do. My current Oppo player have the same capability. Again, make sure you consult the manual. This way your TV will recieve the videosignal and the Onkyo/Emotiva the audiosignal, independently of one another. One of the advantages of doing this is also that each HDMI cable only has to do one task, as oppose to video and audio being transferred through the same cable. In theory it may bring improvements over the latter option.
In other words, for this you will simply need two HDMI cables. When connected this way your Onkyo receiver will not carry out any video switching or processing duties. Audio only.