[IIINeOIIINL]

There may be a problem with OS X or XBMC that makes audio work for some and not others, but it seems the first thing to check would be all the settings. Given that there are so many settings that affect audio, it seems to me people have been pretty sketchy about what their settings are.

Surround sound audio (AC3 and DTS) is working for me on a Mac mini with OS X 10.8.2 (Mountain Lion), and XBMC 12 (Frodo RC3), with audio going out optically. The receiver's DTS icon lights up (for DTS) and I hear surround sound. Maybe some people for whom it is not working would like to report their settings the same way, or try these settings, and maybe a pattern will emerge.

XBMC, Settings > System > Audio Output
Audio Output - Optical/Coax
Speaker Configuration - 5.1
Boost volume level on downmix - Off
Output stereo to all speakers - Off
Dolby Digital (AC3) capable receiver - On
DTS capable receiver - On
Audio output device - Built-in Output

OS X, System Preferences > Sound > Output
Digital Out - Optical digital-out port

Audio Midi Setup > Built-in Output > Output
Source - Digital Out (not actually a setting, just info in the window)
Format - 44100.0 Hz 2ch-24bit Integer

I don't profess to understand the settings and don't know which are important; I more or less come to them by trial and error. Maybe it will help someone.

Another thought, I don't know if a bad optical cable is a possibility?

I Can confirm this too, using the exact same settings like above.
I even cannot select more then 2 speakers in the Audio Midi setup, I don't know if this is a ML 10.8.2 bug or something I'm not seeing here.
Strangely Dolby Digital 5.1 and DTS are working, but sometimes I got the idea that its not function properly, when I'm watching a moviescene with only people talking and after that some special effects or music, the volume difference are big. I don't know if this something depending on the audiomixer of the moviecreators or a wrong config in XBMC or ML.

[houser]

[quote='Glorious1' pid='1310596' dateline='1359069102']

Audio output device - Built-in Output

Thanx for reply!

If I use that setting, sound comes out of the speaker of the Mac Pro.
I need to set it to optical out to get sound out of my Mac Pro (works on xbmc 11 Eden).

If I set output to optical out in 12rc3 , xbmc starts to stutter and will not boot after quit.
Opening XBMC 11 Eden and setting it to another audio output makes 12rc3 boot again.

When starting XBMC 11 Eden, there is another output device called "default output" which works just fine.
That output is never visible on my system, using XBMC 12 Frodo rc3

This is on a Mac Pro, using ML. 10.8.2

Hope this helps

[Glorious1]

I Can confirm this too, using the exact same settings like above.
I even cannot select more then 2 speakers in the Audio Midi setup, I don't know if this is a ML 10.8.2 bug or something I'm not seeing here.
Strangely Dolby Digital 5.1 and DTS are working, but sometimes . . .

I think only two speakers are supposed to show when you choose 'Speaker Configuration' in Audio Midi Setup. That's the way it is for me and the output is fine. It seems like you got surround sound to work. I don't know if the volume differences are another problem or that's the way the film sound was designed?

@ houser - Are you sure you're not mixing up two settings in XBMC?
at the top: Audio Output - Optical/Coax
and at the bottom: Audio output device - Built-in Output

It does sound like you're having some strange experiences. Hopefully someone who understands the whole sound system can sort this out at some point.

[houser]

@ houser - Are you sure you're not mixing up two settings in XBMC?
at the top: Audio Output - Optical/Coax
and at the bottom: Audio output device - Built-in Output

Thanx Glorious1!

I am pretty sure I am not mixing up anything at all.
Behaviour is however still exactly as the Original Topic starter covers and the song remains the same..

[Memphiz]

Optical is only 2.0 channels. DTS and AC3 is encoded in these 2 channels and get decoded to 5.1 by the receiver. Its not a bug of OSX its how the standard for optical is. You can either transfer 2.0 PCM sound (stereo) or encoded formats which uses these 2 channels for transmitting encoded multichannel data.

[Glorious1]

@ houser - Are you sure you're not mixing up two settings in XBMC?
at the top: Audio Output - Optical/Coax
and at the bottom: Audio output device - Built-in Output

Thanx Glorious1!

I am pretty sure I am not mixing up anything at all.
Behaviour is however still exactly as the Original Topic starter covers and the song remains the same..

If, as you say, you are really seeing and able to choose a device called "optical out" under XBMC >
Settings > System > Audio output > Audio output device
and not under
Settings > System > Audio output > Audio output,
then I suspect something is screwed up in Audio Midi Setup. By default there is no device called "optical out" there. Do you have one? If so, you must have created it. FYI, here is my Audio Midi Setup window. I did not create any device here. You shouldn't need to I don't think.

[houser]

If, as you say, you are really seeing and able to choose a device called "optical out" under XBMC >
Settings > System > Audio output > Audio output device
and not under
Settings > System > Audio output > Audio output,
then I suspect something is screwed up in Audio Midi Setup. By default there is no device called "optical out" there. Do you have one? If so, you must have created it. FYI, here is my Audio Midi Setup window. I did not create any device here. You shouldn't need to I don't think.

OK

Edit:
See from your sig that you have an Macmini. I would guess your "built-in output" is then an optical out?

If so, you probably don't have the problem outlined in this thread?

On a Mac Pro, the "built-in output" is the speaker output.

FYI see pic if you are interested FWIW:
On a Mac Pro under 10.8.xx you have some more audio options by default:

[Glorious1]

No, I'm definitely using optical out. That's the only connection to the receiver in the system. The HDMI goes to the TV only and that is a dead end. And no, I don't have the problem listed in this thread.

OK, I didn't realize you had a Mac Pro and that has some different options. Still, I don't see a device called "optical out". I would think there would have to be such a device for you to select it in XBMC under "Audio output device". In my case, when I scroll through the options in XBMC for that setting, it shows only the devices listed in Audio Midi Setup.

I'm guessing here, but it seems System Preferences > Sound allows you to select a "device" for sound. In my case that is called "Digital Out", and it is targeted for the optical digital-out port. Then, Audio Midi Setup uses that as a source to a new device for actual output. In my case that device is called "Built-in Output". That is what I need to choose in XBMC under "Audio output device". It doesn't make a lot of sense, but these things rarely do.

So if you find a device in Sound preferences that uses the optical port, select that, then in Audio Midi Setup find the output device that uses that as a source, select that, then in XBMC select that under 'Audio output device', maybe there's a chance it will work.

In case it helps, I'll post all the other two audio setting pics:

(I changed the XBMC Speaker Configuration to 2.0; it doesn't make a difference apparently what that is set to. I guess that's because, as Memphiz, it goes out as 2 channels and is decoded by the receiver anyway.)

[Memphiz]

Speaker Configuration only is taken into account when receiver is able to receive LPCM (which is only available on HDMI). Not sure if we could force speaker configuration to 2.0 whenever optical is set - DDDamian would have an answer to that i guess.

[DDDamian]

If Optical is set, multichannel LPCM is sent as 2.0. The multichannel LPCM setting should be disabled by default if optical is chosen. As Memphiz states, normal SPDIF (optical/coax) standards only allow 2.0 LPCM and surround must be sent over two channels, then decoded at the receiver end.

Passthrough (encoded) formats basically ignore the speaker count, which is why surround is heard no matter the speaker setting. Auto-forcing the actual speaker setting to 2.0 for optical would make sense, just not currently done. It's only forced internally.

This is how it should work - if you see otherwise report it here. I don't have any Apple gear and the code for Apple (CoreAudio) is different than the platform I use.

[Glorious1]

Thanks very much Memphiz and DDDamian; I guess that explains why it doesn't matter what I set XBMC's Speaker Configuration to when sending out optical. Just one question. Wikipedia's article on LPCM (http://en.wikipedia.org/wiki/Linear_puls...modulation) has this line:

"RF64 container format (defined in 2007) uses LPCM and also allows non-PCM bitstream storage: various compression formats contained in the RF64 file as data bursts (Dolby E, Dolby AC3, DTS, MPEG-1/MPEG-2 Audio) can be "disguised" as PCM linear."

Is this what is happening when we send AC3 or DTS out on the 2-channel optical port, and what you mean when you refer to LPCM?

[DDDamian]

Essentially yes. What we call around here passthrough formats (encoded data) are typically sent in data packets with defined headers and packet sizes. Sometimes these are arrayed as headers and data bursts.

PCM (or a variant LPCM) is the standard for raw pulse-code modulation, basically amplitude over time. Formats like mp3 (frequency over time) or FLAC (losslessly compressed PCM) and sometimes encoded formats are decoded to PCM for playback.

Ultimately inside receivers everything gets converted to PCM, so digital audio is largely about compression fomats, bitdepths and samplerates, and lossless/lossy formats, all ending up as PCM eventually.

[baalin]

I have been having very similar issues in that sound did not work for some videos with MP3 based sound tracks, MP3 files would not play, and no sound while streaming Pandora over airplay from my iphone/ipad.

My settings (No idea how to set the midi stuff):
Mac OS X 10.8.2
XBMC, Settings > System > Audio Output
Audio Output - HDMI
Speaker Configuration - 7.1
Boost volume level on downmix - On
Output stereo to all speakers - On
Dolby Digital (AC3) capable receiver - On
DTS capable receiver - On
Audio output device - HDMI

OS X, System Preferences > Sound > Output
Digital Out - HDMI

I did notice that if I changed the Speaker configuration in xmbc from 7.1 to 5.1, I have sound from Pandora over Airplay.

[Memphiz]

finder->applications->utilities>audio midi setup

ensure to set the speakers to 7.1 there too.

[houser]

Just spend a lot of time testing all possible variations on settings on the ML 10.8.2 and rc3 combo and the problem outlined in OP seems to be 100% reproducible
at least on my system ( Mac Pro 3,1) and AFAIK.

The one thing that might possibly be useful ( but probably not) was that I managed to have stereo PCM audio working for a while
out the coaxial digital by setting the output to Airplay (?).
Could not reproduce it after more tests though. Perhaps my computer was just confused there for a bit after all the settings tweaking

Will someone be kind enough to post in this thread if there is a nightly worth testing in this regard? I am subscribed and happy to test it when you guys have time to look at it.

thanx again and keep it up!