Problem with 6 channel audio in MOVs
#1
I have an ASRock ION 330 running Jaunty, using th SPDIF out for digital audio. I'm getting AC3 and DTS surround out just fine from AVIs and MKVs, but I have some 1080p trailers in MOV format which have 6 channel audio, and it only plays back in Stereo the L & R, dropping all other channels.

Codec info on playback says:
Audio: aac, 48000 Hz, 6 channels, s16

Other sources show codecs including ac3, dca, and work fine via bitstreaming.

Is this problem fixable, to deliver surround output? Is this an XBMC problem, or is there some alsa mojo that can be applied?

Thanks.
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#2
Hmmm. Edit didn't come through...

For music files (DTS & AC3), using Paplayer also drops all but L+R, while DVDPlayer bitstreams them fine.
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#3
Dortamur Wrote:I have an ASRock ION 330 running Jaunty, using th SPDIF out for digital audio. I'm getting AC3 and DTS surround out just fine from AVIs and MKVs, but I have some 1080p trailers in MOV format which have 6 channel audio, and it only plays back in Stereo the L & R, dropping all other channels.

Codec info on playback says:
Audio: aac, 48000 Hz, 6 channels, s16

Other sources show codecs including ac3, dca, and work fine via bitstreaming.

Is this problem fixable, to deliver surround output? Is this an XBMC problem, or is there some alsa mojo that can be applied?

Thanks.

With SPDIF connection you are limited to 2.0 LPCM or AC3, DTS bitstreaming due to bandwidth limitations. Mov files usually contain AAC encoded audio which can not be bitstreamed to the receiver (or if it could your receiver can not decode it).

So to achieve 5.1 multichannel LPCM you need to use hdmi connection to your receiver. I will put up a detailed guide how to do it. Just look for my thread in the next week.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.
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#4
Am I out of luck doing this with my Mac Mini which only has the mini-audio to toslink out? HDMI is passing over video only.

I am seeing the same thing, by the way. Well a little different. Any MOV file with 6 channel AAC audio I hear some channels but not all. In most cases I hear no voices in the trailers I am attempting to play.

AAC trailers in 2 channels play just fine.

Is there a known fix for the Mac Mini and these files?

Using a Mac Mini under jaunty, latest SVN just before the library went south. 6 Channel audio is working fine under DCA mkv files.

Would be a bummer if the Mac Mini is incapable of doing 6 CH AAC out under Linux, might be the jump I need to move to the Ion really.

Edit: By the way I know these trailers had working 6 channel sound when I was running XBMC under OSX, so is this a Linux limitation?
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#5
BDPNA Wrote:Am I out of luck doing this with my Mac Mini which only has the mini-audio to toslink out? HDMI is passing over video only.

I am seeing the same thing, by the way. Well a little different. Any MOV file with 6 channel AAC audio I hear some channels but not all. In most cases I hear no voices in the trailers I am attempting to play.

AAC trailers in 2 channels play just fine.

Is there a known fix for the Mac Mini and these files?

Using a Mac Mini under jaunty, latest SVN just before the library went south. 6 Channel audio is working fine under DCA mkv files.

Would be a bummer if the Mac Mini is incapable of doing 6 CH AAC out under Linux, might be the jump I need to move to the Ion really.

Edit: By the way I know these trailers had working 6 channel sound when I was running XBMC under OSX, so is this a Linux limitation?

You can't bitstream AAC audio over hdmi. I don't know about Mac mini hardware but you have to get hdmi audio working. Check your aplay -l output if you have hdmi audio device recognized.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.
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#6
So basically, there's no way to bitstream AAC 6 channel out no matter what then? Maybe it's just not possible to get 6 channel sound out of Apple MOV files with AAC sound?
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#7
Ah right! Because aac is software decoded, the SPDIF doesn't have the bandwidth for the 6 ch PCM. That makes sense. HDMI is the recommended solution - but isn't always practical or possible (in my case, all my AVRs HDMI ins are used already).

However, I still think there should be a better solution than just playing LR and dropping the rest - especially the centre which is the primary source for dialog.

The easiest would be to downmix to Stereo - not ideal if there's a Surround solution though.

Harder would be to transcode the 6 ch PCM into something that can be bitstreamed. Even if it's basic AC3, that'd be better than a stereo downmix.

I thought I read somewhere that ALSA was configurable to do this, hence my query about a magic ALSA config.
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#8
Wow, this is all pretty eye-opening to me. So why is it that DCA 6-channel audio (what MKVs use) is working fine, but not 6-channel AAC? A different way that DCA is handled over SPDIF? My mac mini handles that perfectly.

If the mac mini can't handle 6-channel AAC out of SPDIF no matter what I do, I'll just get an Asrock Ion and use the HDMI out. That is a major limitation in my book.

If there's a way to on-the-fly convert the AAC to AC-3 using Alsa, that would be fine with me, too.
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#9
Little advice, before changing your hardware for an hdmi output motherboard, check if your receiver handle 5/7 channels LPCM streams on hdmi.

I have a Yamaha sound projector with hdmi 1.3a connections but it only handles 2.0 LPCM on hdmi. It's a 5.1 receiver but it seems when is was built, more than 2 channel LPCM didn't exist.

That's lame as there's nothing in hardware part preventing such functionality, just not handled on firmware parts of the receiver.


For your .Mov multichannel AAC, just check Downmix to Stereo in xbmc audio settings. It will only downmix multichannels files that ar not bitstreamable on your hdmi, so DTS and AC3 will keep multichannels.

Regards.
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