5.1 Channel Placement Issues

[YouCAD.67]

I am confronting a problem which I have never experienced before.

When importing a .mov into DCP-o-matic, the program seems confused with where the audio sources are (or if they are there at all) for a 5.1 export.
I am using Davinci Resolve 19 on an M1 Mac Mini, Sonoma 14.2.1

have tried:
• exporting the full mix on a single 5.1 track
• exporting the full mix on a single 5.1 Film track
• exporting all 6 stems as mono tracks
• doing all of the above as both AAC and PCM
• doing all of the above with the Output Track setting in Davinci as both "Bus 1 (5.1)" and "All Timeline Tracks"

No matter what I do, DCP-o-matic opens the file with the same issue.

This image is the initial appearance of the channels when I first import the .mov into the program

Screenshot 2024-11-01 at 12.02.38 PM.png

This is the selection that allows for the audio that allows for the most accurate audio playback (excluding Ls and Rs, mentioned below)

Screenshot 2024-11-01 at 12.03.08 PM.png

Lfe sharing 3:1 with C is really tripping me out because it seems to be mixing them up (Lfe is playing back what should be C and vice versa), but in a peculiar way as C will only play back the low end on 3:1 and not 4:1 as I had expected if they were truly confused.

Ls and Rs aren't playing back no matter what box I check, but when I play the .mov via Quicktime on my 5.1 setup, every sound comes from every speaker it should.

And just for clarity: every channel is in the appropriate order for the full mix on a single 5.1 track, or when I try to export it all as individual mono tracks. I've double, triple, and quadruple checked this.

I would really appreciate some help here as I have exported many DCP's without trouble until now thanks to DCP-o-matic being extremely simple, but today has thrown me for a loop.

[IoannisSyrogiannis]

First of all, you should know that -by default- DCP-o-matic is down-mixing for monitoring. If you don't want it to do so, you need to let it "know" on the preferences.

It makes a difference if the audio channels are discrete or interleaved. If they are discrete, and there is no info on what is what, DCP-o-matic will map them all center and it's up to you to choose what goes where. If they are interleaved, it will most probably choose according to the mapping of the channels. From your screenshots, it seems like the audio channels are discrete.

[YouCAD.67]

Thanks for getting back to me.

In the sound preferences I have it set to my 5.1 receiver (consistent with how I've always had it) so there is no down-mixing happening there, and the audio is not discreet either.

As you can see in my second image, when I attempt to map the channels they either don't exist according to the program (Ls and Rs, which do when played back via Quicktime) or they exist in the wrong place (C and Lfe).
To reiterate: I left Ls and Rs blank to show that they don't function with any row I map them to, and I put C and Lfe on the same row because they both only play back from there, despite C playing what should be from Lfe and Lfe playing what should be from C.

In the second image, I'm using the graph as a visual representation of what works, where it works, and what doesn't.

[IoannisSyrogiannis]

7xDiscreteAudioChannels.PNG

5xInterleavedAudioChannels.PNG

Have a look at two examples.
The first, is a ProRes file with 8 discrete audio channels for L, R, C, LFE, Ls, Rs, Lt and Rt.
The second, is an MKV file with 6 interleaved channels for L, R, C, LFE, Ls, Rs.
You will notice the difference between them on where the discrete pcm files are shown separately in the list (near the content, the 1:1, 2:1, etc are not under the same group, like the "eng(ac3)" in the other case, the same happens on your examples) and there is nothing to distinguish what channel is what. DCP-o-matic will not map them, because it doesn't "understand" if the whole thing is a mono audio for eight different language streams, or four stereo, or stereo and M&E, with and without songs in the original language and so on and on...
You need to "tell" DCP-o-matic what is what. If one audio channel is C and the other LFE, you need to clarify yourself.


Almost the same if you had separate .wav files. If the files were not named on their files as L, R, etc., but instead had some kind of from Title_FinalGradeBio_3432x1716_4444XQ_LtRt_LRCLfeLsRs_210913_audio_1, ...audio_2, ...audio_3, etc. You would need to go to each file in the content list and map it yourself. If they were named in some kind of form Title_FinalGrade_L, Title_FinalGrade_R, Title_FinalGrade_C, etc. the mapping would most probably made automatically (that is my experience, but that was not without exceptions).

If, on the other hand, you had six interleaved audio channels in the same stream. You wouldn't have to do something.

I hope the demonstration helped. Best of luck.

[Kewl]

Ah yes, the infamous MOV with multiple mono audio streams for surround* rather than one multichannel stream.

Assuming your audio is L R C Lfe Ls Rs, select stream #1 for L, stream #2 for R, and so on. Just do a diagonal in the audio tab.

* AJA Ki Pro produced MOVs like that.

[YouCAD.67]

As I have stated multiple times already, the bottom second example is what plays back closest to properly.
If I just selected everything diagonally, I am going to have no Ls, no Rs, and no C playing back. It will remain as L, R, and Lfe.
That is hardly acceptable for any kind of exhibition.

[carl]

Maybe we can try to narrow down a bit where the problem is.

By mapping one of your "known good" source channels (e.g your 1:1) to L, R, C, Lfe, Ls, Rs in turn in the audio tab, can you get the channel to come out of each of your physical speakers (when previewing in DCP-o-matic)?

In other words, if you map 1:1 to L (green square only on the 1:1/L intersection) you should hear something out of the L speaker. Mapping 1:1 to R something out of R, and so on.

If that works, something funny is happening with the mapping of source channels to DCP. If that doesn't work, we have a problem with how DCP-o-matic is copying audio channels to your sound card.

We can probably do a zoom call to check this out if that's easier.

[Carsten]

It all depends on how Davinci actually flags and packs the audio tracks. You should maybe look at the master file with some media file inspector and try to find out what is actually in it.

If you can identify the tracks by listening to them in DCP-o-matic, just remap them as you need them.

[Kewl]

What does MediaInfo https://mediaarea.net/MediaInfo reports on the exports with PCM?

Also, maybe some audio channels are in the file, but they are empty. You could open the exported file in a DAW or an audio editor to visually check out the audio.

[Kewl]

I am using Davinci Resolve 19 on an M1 Mac Mini

By the way, on Apple Silicon with multichannel PCM audio via HDMI out, Lfe is channel 3 and Center is channel 4.

In Audio MIDI Setup:

Capture d’écran, le 2024-11-03 à 20.50.02.png