If you want to get BOTH audio sources for the same video, you have to be careful, but there IS a way to do it. I have read posts on the interwebs stating it is NOT possible, but it IS!
This is primarily for those using HDMI inputs and wanting optical audio sources as the same time. Read ahead...
Step 1: Why Both?
I recently upgraded to this receiver, and had some audio problems. The audio quality itself was great, but my ability to specify the channels I wanted for the video were difficult.
The manual was little help.
I have 2 HDMI A/V sources I wanted, and I wanted both audio (HDMI and optical) sources from each.
1 audio source (U-verse) did NOT send surround sound audio through the HDMI cable to the receiver (cable box), and 1 audio source (PS3) will send LMCP (7.1 SS) but not everything else I wanted. Most of what I wanted was audio from the optical cable which the receiver can decode into DolbyDigital.
So, the problem with this receiver is that I wanted the video interconnections to go through HDMI (routed to the TV), but most of the audio has to go through your optic ports, AND I wanted the option to select either audio source.
NOTE: As I was writting this up, U-Verse updated their firmware for my local (first local to get it), so HDMI is passing DD SS.
Step 2: How?
The manual states you can select audio channels for your inputs. While this is true, it does not tell you that your video channels CANNOT be selected this way. So, a tricky reconfiguration is needed.
First, connect your HDMI VIDEO sources. There are 3 HDMI inputs, since this guide is focused on HDMI input, and you probably have this receiver for these inputs, this is where to start. Keep track of where you have your video source inputs. This will be useful later when switching audio. The VIDEO input will be where you select your VIDEO on the remote. Ex. if you use your BD HDMI input, then your BD remote button will select this HDMI input. Both audio and video will be on this selection as routed through the HDMI cable.
Second, connect all your audio options. There are 2 optical audio ports. Keep track of which audio sources these are for. This is where you will match them up in your settings.
Third, set each optical port source to whichever input you want. This is the important part! This is where you will tell the receiver where you want the optical audio to be routed. You will be able to select this source on your remote after designating the channel you want this routed to. I found this to be tricky. Ex. I have 2 HDMI audio sources connected. So, those buttons on my remote work as described. I also have 2 optical audio sources from those same sources routed to my receiver. I needed to find 2 OTHER audio sources, (not the HDMI sources already used).
Fourth, now you will be able to select the VIDEO source (HDMI) you want to watch, then the audio source. If you want the HDMI audio, then you need to do nothing. You selected that source! If you want the optical audio, you THEN select the audio source for it's optical audio. If you select the second audio source (optical) on your remote BEFORE selecting the video (HDMI) you will hear the audio, but see nothing.
So, if you have 2 HDMI sources and you want their 2 optical audio sources as well, you will be using a total of 4 designated sources (buttons on your remote) to get this done. This is all due to how the video is channeled in the receiver, and is not immediately obvious. Simply set the optical audio for a DIFFERENT selection and use it AFTER you select the video.
I hope this helps anyone else who has this receiver, and the same problem I had.