Unable to get multi-channel audio

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Level 1

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Unable to get multi-channel audio

Hi,

I have a fairly new Mac Mini which I bought a couple of months ago (running 10.8.2). Up until now, I've just been playing the audio through my HDMI cable to my TV, which in turn runs to my Sony receiver by toslink, today I finally had some time to set up my surround and I can't get it to work.

At first I just assumed my Mac knew that my TV can't process digital signal, but now that I've gone directly to my receiver from my Mac by optical I've realised the fault is somewhere else. This makes sense as my TV is also brand new and quite a high spec. (Samsung UE40D6100)

My receiver is capable of Multi Channel, but no matter what I do in the AudioMidi setup, all the multi channel options are greyed out.

This is true for both my HDMI output and my Digital Optical. On looking at my system profiler I can now understand why I can't have multi channel on HDMI (see screenshot). That's OK as long as I can use digital optical. My receiver doesn't have any HDMI ports anyway.

I've trawled the web but there just seems to be a lot of people asking the questions and no answers?

Can anybody help?

Thanks.

(oh dear, i've just seen 'audio' is the most popular tag on tickets. That doesn't bode well. Certainly marries with what I saw on the web today)

Mac mini (Mid 2011), OS X Mountain Lion (10.8.2), 8GB RAM. Sony receiver with DD&DTS

Posted on Nov 17, 2012 4:57 PM

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Answer 1

LousyFool

Level 4

2,678 points

Nov 19, 2012 4:33 AM in response to _xstoph_

This might not help you since you don't have an HDMI input on your receiver, so you can't test, but anyway:

I have the surround options also greyed out, but magically I do have surround sound via HDMI, and it's not only the ProLogic thingy that's coded into the stereo signal but sounds like AC3.

However, I'd also be interested in hearing from an expert what's (not) happening...

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Answer 2

_xstoph_ Author

Level 1

0 points

Nov 19, 2012 5:19 AM in response to LousyFool

Well what I've discovered in researching this is that the MacMini won't output multi-channel audio over Optical, only HDMI.

My receiver can receive multi-channel by Optical, but as I have to run it via my TV which the Mac knows only has two speakers, it greys out the options. It's quite frustrating because I think (I could be wrong, I'm not an audio expert yet) that it would be technically possible for the signal to be passed through my TV to my receiver if only the Mac would allow it. If only there was a way to override the Mac not offering the choice.

What I suspect is happening in your case is the encoded multi channel signal is being passed to your receiver by HDMI within the two channels, and your receiver is decoding it and giving you surround. There's a chance that might sound very wrong to an expert though :-)

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Answer 3

LousyFool

Level 4

2,678 points

Nov 19, 2012 5:34 AM in response to _xstoph_

Well, HDMI can transport up to 8 discrete channels, so AC3 is a piece of cake for it, no limit to "encoded within two channels" such as ProLogic...

I'm not sure why you have to feed the optical cable into the TV first, why not straight into the receiver? If you want 5.1 or so, the receiver is the only one able. Being a "real Mac", the Mini should put multichannel audio out over optical as well, or where do you have your info from?

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Answer 4

_xstoph_ Author

Level 1

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Nov 22, 2012 5:59 AM in response to LousyFool

I am feeding the optical to my receiver. I have my Mac connected by HDMI to my TV, and my TV connected via optical to my receiver. I also have my Mac connected directly to my receiver by optical.

I read somewhere that Mac's only output multi-channel by HDMI, but because I have to run my HDMI to my TV not my amp, I figured it was only sending two-channel.

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Answer 5

LousyFool

Level 4

2,678 points

Nov 22, 2012 6:17 AM in response to _xstoph_

Okay, so let's try to wrap this up:

- The Mini sends multichannel audio not via optical but only via HDMI. (Ignore the greyed-out options in Audio MIDI Setup, but have it set to 2ch-24bit Integer.)

- Your receiver has no HDMI in, only optical.

- Instead, you're feeding HDMI into your TV, and from the TV optical to the receiver, hoping the TV will route the multichannel audio through to the receiver; practically, the TV to work as a "format converter" HDMI -> optical.

- Except, it doesn't work.

Well, now you can blame either one:

- Apple for not enabling multichannel audio via optical, or

- Samsung for their TV not having an audio converter included, or

- your good self for owning a receiver without HDMI in.

Whatever, unless you overlooked a thing in the TV's manual or you're willing to invest more $$$, I guess you'll be stuck with 2 channel audio... sorry...

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