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[6233638]

So this is a bit of a strange one.
I went to watch Life of Pi, which is a film that I haven't got around to converting to MKV yet, and whenever I try to play the disc Zone Switch keeps sending it to my stereo zone and not the multichannel zone.
These play to separate audio devices, so it is essential to do so.
 
The Zone Switch rule for this is the highest priority item on the list, and is as simple as possible:
It routes any file where [Channels]=>2 to the multichannel zone, and stops playback in every other zone.
 
As far as I can tell, this is only happening with discs which contain a 7.1 DTS-HD track.
Discs with a 5.1 DTS-HD track seem to be routed to the multichannel zone correctly, and films with a 7.1 DTS-HD track which have been converted to MKV (including Life of Pi now) are also being routed to the multichannel zone correctly.
What makes it even stranger is that this disc in particular only has multichannel tracks - there are no stereo tracks on the disc at all. (7.1 DTS-HD, 5.1 AC3 in other languages)

[6233638]

Actually, when searching for other 7.1 discs, I've found a couple of 5.1 discs which do this as well.
I have no idea why some discs are correctly routed to the multichannel zone, and others are routed to the stereo zone - even when the multichannel zone is currently the active zone.
So far, all of the discs I have found to have this problem are using DTS-HD.

[6233638]

Any idea what could be causing this?
Would a log file help? (not sure if it logs that sort of thing)

[RoderickGI]

I have no idea...

...but what does the audio path show you?

[6233638]

I have no idea...
...but what does the audio path show you?

It tells me that it's converting from 8 channels to 2 channels.

[RoderickGI]

Okay, so that is why it is switching to the stereo zone; because the output is in stereo! 

Now you just have to work out why MC is down mixing 7.1 to stereo for those disks. That will be much harder to work out. It could be down mixing because the stereo zone has been selected, or it could be selecting the stereo zone because the output is stereo.

I see that the audio is being up sampled to 192kHz first, which is a bit strange for a 7.1 channel audio stream, I would have thought. In some circumstances that would force MC to down mix to stereo. For example, if it thought it was outputting via S/PDIF (just an example). Can you think of anything that might be triggering the up-sampling, or have you specified that to happen?

Anything in the logs?

Of course the obvious thing to suspect is the new DTS-HD functionality in MC, but only Hendrik would be able to analyse that.

[dean70]

What happens if you put the original dtsdecoderdll.dll back in the path?

[6233638]

Okay, so that is why it is switching to the stereo zone; because the output is in stereo!  

The output is stereo because Zone Switch is incorrectly sending it to the wrong Zone.
The Stereo Video Zone mixes everything to 2 channels, the Multichannel Zone mixes everything to 6 channels.

I see that the audio is being up sampled to 192kHz first, which is a bit strange for a 7.1 channel audio stream, I would have thought.

The Stereo Video Zone resamples everything to 192kHz to ensure that audio latency has a fixed value.
If I send my DAC 192kHz for some files, and say 48kHz for others the difference when using large audio buffers can be something like 100ms, which would be noticeably out of sync.
 
The Multichannel Zone resamples everything to 96kHz for similar reasons (96kHz being the maximum rate supported by that device) and the Stereo Music Zone does not resample anything below 192kHz.

What happens if you put the original dtsdecoderdll.dll back in the path?

It is still being routed to the Stereo Video Zone and not the Multichannel Zone.
 
 
I have attached a log, though I don't know that there is anything useful in it.

[mattkhan]

The Stereo Video Zone resamples everything to 192kHz to ensure that audio latency has a fixed value.

nothing useful to add so apologies for the mild OT but curious about this comment, where does the variable latency come from? some fixed length FIR filters? why does that matter exactly? i.e. what would be out of sync here?

[6233638]

nothing useful to add so apologies for the mild OT but curious about this comment, where does the variable latency come from? some fixed length FIR filters? why does that matter exactly? i.e. what would be out of sync here?

My DAC's driver adjusts the buffer size by samples and not milliseconds.
The largest buffer size available for my DAC is 8192 samples.
 
1000 ÷ 192,000 × 8192 = 42.67ms latency
1000 ÷ 44,100 × 8192 = 185.76ms latency
 
Media Center's resampling occurs in a fraction of that time, so it is better to have it resample everything to 192kHz.

[fitbrit]

Could it be that MC is getting the channel info from a different file than the playlist it plays as the main feature?
e.g. a stereo or silent menu animation m2ts
It sounds like MC is incorrectly analysing the soundtrack somehow.

[RoderickGI]

That idea has merit and fits the observations.

There may be a short stereo track at the beginning of playback, which was removed or up mixed during conversion to MKV, so the problem went away once converted.

What happens if you play an m2ts file from the main feature directly?

[6233638]

If I play the m2ts file directly, it gets routed to the multichannel zone, as it should.
There isn't even a stereo track in it.
 
Media Center remembers the last title you picked when you play a disc, and it picked the correct one by default anyway, so it's not that it's thinking the disc is stereo from playing the wrong title.

[RoderickGI]

Okay. Bear with me.

What happens if you play an m2ts from the disk, which works correctly, then stop, eject the disk, put it back in, and play it again normally?

Does it get routed to the stereo zone?

I'm thinking that if there is no stereo track on the Blu-ray, yet zone switch selects the stereo zone, it must be acting on something external to the Blu-ray, and possibly that is related to what was played prior to playing the Blu-ray normally. If zone switch works in the above scenario, then that all but eliminates the Blu-ray as the source of the problem.