Question to the developers. Now that there is a HDMI Mac Mini (not to mention audio-out enabled DisplayPort Macs), should a video with a DTS-HD or Dolby TrueHD track output the bitstream data correctly to a receiver that can decode that data properly? If not, what will it take to get that feature in Plex? Do you just need the hardware?
A mere 3 weeks after I bought a new Mac Mini....I just didn't think apple had it in them.
I’m very curious about this, too. Should have my new mini any day now, so I hope this is the beginning of HD audio on Macs! 
For what it is worth, a CNET review says this:
For audio, the HDMI and Mini DisplayPorts both support uncompressed eight-channel audio, similar to the most recent MacBooks. We confirmed that the HDMI also supports Dolby Digital 5.1 audio by passing it through a receiver. You also get standard analog/digital in and out jacks.
I already received my new Mac mini. The CNET reviewer is correct - when outputting audio via HDMI, the OS uses multichannel PCM. DTS and Dolby Digital passthrough both work as expected.
What about TRUEHD, etc.?
Looks like bad news regarding lossless audio. Below is from a thread on the AVS Forums:
Normal DTS and AC3 bitstreaming work fine, which is no surprise, so that’s good.
Here’s what I tested, all using Bluray rips in MKV container.
PLEX, movie with TrueHD track:
The audio doesn’t play at all, no sound.
PLEX, movie with DTS-MA track:
Plex attemps to bitstream the audio as regular DTS, audio is choppy, the receiver shows a DTS intermittently flashing, it doesn’t work.
PLEX, movie with native 5.1 PCM track (Full Metal Jacket Bluray):
The audio is bitstreamed as AC3 5.1. Say what! This is surprising. I tripled checked, receiver is getting a Dolby Digital bitstream, the file definitely has a PCM audio track. I guess Plex encodes the 5.1 PCM into 5.1 AC3 and bitstreams it.
XBMC, movie with TrueHD track:
This is sent as 2-channel PCM, only the Left and Right are audible and mapped directly, no center channel therefore no dialog is audible.
XBMC, movie with DTS-MA track:
The DTS core track is extracted and bitstreamed to the receiver, the receiver shows DTS and plays correctly, but it is not DTS-MA.
XBMC, movie with native 5.1 PCM track (Full Metal Jacket Bluray):
This is sent as 2-channel PCM, only the Left and Right are audible and mapped directly, no center channel therefore no dialog is audible.
http://www.avsforum.com/avs-vb/showthread.php?p=18797292
The software needs to catch up with the hardware. I think the hardware allows it, but Plex does not yet. From reading around.
I don't think ffmpeg supports TrueHD decoding yet, I may be able to get it to pass through raw via HDMI to your receiver.
I believe DTS-MA contains a core DTS track plus extra fidelity info, but there's obviously a bug somewhere in Plex or ffmpeg preventing us extracting the DTS core track. WIP.
Yup, that's exactly what we do. Works with AAC/FLAC 5.1 as well. Although now with HDMI audio we can send the raw PCM.
XBMC has a different OS X audio module, so has a different set of problems. I think ours is better (but I would given I wrote it ;)).
Basically our HDMI support will be limited until I get my hands on one of the new Minis, which will be when I can afford to upgrade. So hang on tight! In the meantime, 5.1 PCM transcoding works well for any format ffmpeg supports.
-Ryan
Thanks Ryan, this is all good information. I know that I had not been considering a Mini (or Plex) due to the lack of HDMI but now that it's available it's good to see that there will be some consideration down the road for at least doing bitstreaming of the raw HD audio tracks if the hardware can support it.
This brings up another question, would there also eventually be the capability to have Plex automatically select an HD audio track if it is present? Like a lot of people I have been ripping my BD library to .mkv. I keep the original uncompressed HD audio track (DTS-MA, TrueHD or PCM) as well as a Dolby 5.1 track for compatibility purposes. It would be nice if Plex eventually had a preference to select the HD track automatically, whether it is track 1, track 2, etc.
hello, i woes in Apple store today with this problem , they said the 5.1 or 7.1 pcm is working as long You have the right software .
i have mac mini hdmi didnt opened the box yet , this weekend i will install Windows 7 and try to use power DVd 10 with works perfectly on m,y pc with hd sound card when i set to pcm output .... will se if i can test the m2ts files with LPCM and PCM or HD dolby ...im planing to turn the mac mini into XBMC set in the living room .
will post the tests this weekend
Good stuff. I have tested Windows 7 with Arcsoft TMT3 on Mac Mini 2010 and a blu-ray rip of Dark Knight but could NOT get HD audio to bitstream to my AV amp.
When you output LPCM rather than bitsteaming to AV Amp how you know you are actually receiving Hi-Def audio?
So it looks like the hardware is ready and willing we just need the OS/drivers and most importantly SOFTWARE that will make all of this happen! :)
I am now being told by someone who is very knowledgeable about HTPC hardware running under Windows that it is **impossible** for the C2D CPU coupled with the Nvidia 830 graphics card to accomplish this. How did you verify you actually got bitstream output as opposed to PCM output?
It’s a Geforce 320M.
I'm being told that it won't support bitstreaming of HD audio over HDMI either, apparently none of the currently available Nvidia GPU/chipsets can do it.
Sorry guys, my previous post should have said "could NOT get it working".
I have corrected my post.
Does that leave the possibility of Hi-Def Audio software decoding passing LPCM to the AV receiver?
I'm not sure. I don't think that a public decoder for DTS-MA exists yet. In any event it looks like we won't be getting HD audio from the Mac Mini any time soon.
I am sure that is the case. It is going to take new drivers and software to make it happen. I would not agree that they can't do it, they cannot do it given the current state of drivers. However, it could well be impossible if the firmware on the 320M can't be changed.
Yes, there are different ways to get from here to there, but, none of them are going to happen soon. At least I don't give it much chance any time soon. But I don't really care that much personally, DD 5.1, DTS, DTS-ES is fine by me. YMMV!
