[bagofcrap24]

I asked about seeing if it will let you adjust the volume to try and identify weather it is the pi that is not passing the 5.1 audio through or if it's your receiver that doesn't know what to do with what it's receiving.

There is no audio with 5.1, but there is audio in 2.0. The 2.0 is definitively passing the audio through. There is no sound in the 5.1 and therefore no volume to adjust.

Now that I think of it, I am not 100% positive that the 2.0 audio I checked was AC3, but I think so and will double check tonight. All my 5.1 audio is AC3.

At the risk of being the guy in the saying "he who is half wise is completely stupid", I think that the relevant part of the log runs about 100 lines starting just before line 1100, part of which (the OMX lines) I have excerpted here:

Sorry I didn't realise you had posted a log already
Not sure if this is an important line to tell what is happening

Code:

1139 00:33:17 444.043945 T:2547647568   DEBUG: COMXAudio::PortSettingsChanged - bits:0 mode:0 channels:0 srate:0 passthrough

I would read that as it is passing through nothing.
Incidentally I have just checked a 5.1 ac3 test video and that is passing through fine for me.
Do you have a sample file or anything

Edit: Ignore this, just compared with one of my logs which appears almost identical.