DCP with mixed Audio channels output

[mrwaits]

Hi everyone,

let me start by saying that I am kind of a noob.

I've made several DCP's from MKV files with dcp-o-matic which have been ok but I seem to be facing a strange issue.

I made a DCP from a bluray source. I extracted the mkv with the only audio track I needed: DTS-HD M 5.1.
I assume makemkv gets the audio properly because it has done so before.

I doubled checked on DOM that the audio channels are correctly setup. I even isolated channels and listened to the preview (however I am limited to a stereo setup on my work computer).

I made the DCP but when I tested it on the screening venue the channels were messed up.

In dialogue scenes one actors voice would be coming from the center, but the other actor talking to him would be coming from the left.
There was a sound technician there, I'm confident the he knows what he was doing and he says the channels were coming in wrong.
I think I had o the R channel what should be Ds.

Would it make any sense that DOM might be taking the 5.1 mkv audio and converting it to a stereo DCP because the computer I am using has a stereo soundcard output? (I'm sorry if this is very stupid).

Is there anything I can run to try and see what could have gone wrong?

Thanks in advance.

[IoannisSyrogiannis]

If you still have the project, did you check the graph of the audio levels? Anything unusual?
On transcoding, did you choose any audio processor?
What is DTS-HD M? Do you mean MA? If not, what?

You write that you isolated channels and listened to the preview. What does that mean?
Was there dialogue coming from the left channel at the specific scene?
(If you isolated channels, it wouldn't matter if your output was stereo or mono. An isolated channel would have been heard.)

DCP-o-matic does no conversion other than what you set it to. Check your settings. If you have used some version (?) of the program a lot, you should be familiar with them.
My wild guess (that's the only thing I can do with that info), is that the original audio has those irregularities. Let us know.

[mrwaits]

If you still have the project, did you check the graph of the audio levels? Anything unusual?
On transcoding, did you choose any audio processor?

Checked. No irregularities.
While transcoding I did not select any audio processor.

What is DTS-HD M? Do you mean MA? If not, what?

Yes MA sorry for the typo.

IYou write that you isolated channels and listened to the preview. What does that mean?

I muted all channels (except center) and got the voice correctly coming from that channel.

I also installed Audacity had a look at the sound mxf. It has 5 channels and all seems to have been done properly.
The original audio seems ok. I also checked the MKV it does have the correct audio.



I should have added more information, my apologies.

I also should note that another film with 5.1 sound was played and all channels were used properly. I am going to try and see if the DCP server has any audio options for specific DCP's that could be messing up mine.

[Kewl]

I also installed Audacity had a look at the sound mxf. It has 5 channels and all seems to have been done properly.
The original audio seems ok. I also checked the MKV it does have the correct audio.

Five or six? If it's 5.1, it should be six.

It's also quite possible that some dialogues are panned left or right. What are the characters position on screen?

[IoannisSyrogiannis]

[...]
I muted all channels (except center) and got the voice correctly coming from that channel.
[...]

So, since you did that only for center, the question still stands:
Was there dialogue coming from the left channel at the specific scene?

Again, my impression is that those irregularities on the dialogue are at the original audio. I see no way for DCP-o-matic to partially move around audio. In the process of troubleshooting, you can rule that possibility out.
Now, for the curiosity of it, I would be happy to continue the dialogue. But, according to your input, there is no gain to examine DCP-o-matic for arbitrary mixing. You better look elsewhere.

[Carsten]

Usually you can easily see basic channel assignments when watching the audio in e.G. Audacity. You can not tell L from R or Surround Left from Surround Right, but the L/R, Center, LFE, Surrounds can clearly be identified for most typical mixes.

Bildschirmfoto 2024-10-17 um 13.43.09.png

Audacity should be able to load both the audio from the original MKV, as well as the audio MXF from the DCP created. You should be able to identify a potential problem.

There are also official Channel-Test DCPs available which play specific tracks out of specific speakers, so you can easily hear wether there is something wrong with the channel assignment in the theatre.

[mrwaits]

I also installed Audacity had a look at the sound mxf. It has 5 channels and all seems to have been done properly.
The original audio seems ok. I also checked the MKV it does have the correct audio.

Five or six? If it's 5.1, it should be six.

It's also quite possible that some dialogues are panned left or right. What are the characters position on screen?

I meant 6. (sorry!).

And yes you are right. When the sound was coming from the left the character was on the left. It happens only a few times and is normal. The issue is that only one voice of the characters was coming from the center speaker. Which was weird. Like the center channel had split? Does this make any sense at all?

[mrwaits]

Audacity should be able to load both the audio from the original MKV, as well as the audio MXF from the DCP created. You should be able to identify a potential problem.

Yeah I did. I tested both the mkv and the mxf sound file on the DCP. Looks normal (to me). Please have a look at the attached screenshot.

I'm going to try and see if the server is messing something up.


My backup plan would be to try converting the mkv with only stereo sound.
I also just saw on the DOM manual that i can "Use a Mid and Side (M/S) processor to create a centre channel".

Would you be able to help with the best way to try this option?
Should select 4 -L/C/R/Lfe as is changed by default or should I increase to 5.1?
Thanks!

[Kewl]

This looks pretty standard. I would venture to say that what you're hearing is intentional on the part of the director and mixer. And, if it's not (a dialog track wrongly routed, it happens), they were asleep at the mixing board...

[Carsten]

This looks okay to me. Either you experienced a misunderstanding in the auditorium, or their sound system is messed up. Which does happen.