Channel configuration seems wrong in 7.1 surround

I made a 7.1 surround mix of my feature film in Resolve and tested it in a movie theatre. In Resolve, there appear to be two options for 7.1: "surround" and "film." From what I can tell, the only difference between the two should be the side and rear channels are swapped.

E.g. L, R, C, LFE, Ls, Rs, Lsr, Rsr versus L, R, C, LFE, Lsr, Rsr, Ls, Rs

In practice, when I use 7.1 "surround" and play the file in an actual movie theatre, the channel layout is entirely different.

What I expect: L, R, C, LFE, Ls, Rs, Lsr, Rsr
What I hear in the movie theatre: L, R, L (again), R (again), Lsr, Rsr, C, LFE

While I expected only the side and rear to be swapped (since I didn't use 7.1 "film"), channels 3-8 all seem to be wrong.

Fortunately the theatre was kind enough to let me test my movie in advance while they were closed, so I could go home and rearrange my audio tracks so the dialogue only track was on channel 7 (labled Lsr in Resolve) etc. After rearranging the audio based on what I heard in the theatre, then my movie sounded fantastic in the theatre. Albeit in 5.1 instead of 7.1, because the first and third channels both went to the same speaker, and the second and fourth channels went to the same speaker. The Ls and Rs speakers in the theatre were silent for the whole movie, which was disappointing because I had specific sound effects in mind for those speakers.

I asked the theatre to play me a Hollywood movie in 7.1 while they were closed, so I could compare. The Hollywood movie sounded exactly as expected in 7.1: dialogue from front center, sound effects from the sides, music from the rear. So I don't think the movie theatre has its speakers mixed up.

Has anyone else been making their movies in 7.1 surround? I've read the manual, I've read forum threads, I've watched tutorial videos. It seems like I'm doing everything right. The audio I hear in the theatre is isolated, just going to different speakers than what I expect it to go to. And for some reason even though my audio file has 8 channels, it's only going to 6 speakers.

I've attached a DRP which I created in Resolve 17 and tested in the theatre, then updated to 18 Beta and rendered again, and tested that in the theatre to confirm the behavior is still the same when rendering from 18 Beta.

If anyone can look at my DRP and tell me what I might be doing wrong, I'd appreciate any guidance. Of course my test wav isn't going to work, but you can replace with any audio to hear what track it is meant to be on versus what track it will actually be on.

Thanks in advance for any help sorting this out.

7.1 SMPTE = L, R, C, LFE, Lss, Rss, Lsr, Rsr
7.1 Film = L, C, R, Lss, Rss, Lsr, Rsr, LFE

Channels run in pairs:
Left/Right
Centre/LFE
Left Side Surround/Right Side Surround
Left Rear Surround/Right Rear Surround

Are you delivering a DCP from the Deliver page presets or delivering audio only?

Thank you for taking the time to reply. That makes sense about the channels being in pairs, and I do hear Center and LFE next to each other, just as 7 and 8 which still confuses me because it doesn't match either of the two configurations you listed: SMPTE or Film.

I am delivering a DCP from the Deliver page presets.

Additionally, I also output a Quicktime MOV which included video as well as 8 channels of audio.

The theatre manager let me know he used the Quicktime MOV in the test, because that is apparently faster to play through the projection system than loading up a DCP. Might that impact the channel order? Since the DCP and MOV came from the same DRP in Resolve, would the channels/bus still be the same order? Or does MOV juggle the audio channels around? I've Googled this, but can't find anyone else who's asked these question or posted about having this problem.

Thanks in advance for any continued replies and guidance!

I am delivering a DCP from the Deliver page presets

Which channel configuration was selected with the DCP preset?

Options include:
Wild Track
7.1 DS
ISDF 7.1 DS
ISDF 7.1 SDDS

Since the DCP and MOV came from the same DRP in Resolve, would the channels/bus still be the same order? Or does MOV juggle the audio channels around?

AAC uses a different channel order to LPCM which follows SMPTE recommendations.

LPCM = Left, Right, Centre, LFE, Left Surround, Right Surround
AAC = Centre, Left, Right, Left Surround, Right Surround, LFE

I don't see those DS/ISDF/SDDS values anywhere. I'm using the current Resolve 18 Beta. Maybe what I'm using is not a preset. It's not the colored icons at the top like "YouTube 1080p" and "Vimeo 1080p". I don't see any DCP icons up there. When I choose Format = DCP then it shows different other settings beneath it. Codec = easyDCP, Type = 4K DCI. When I click to the Audio tab, the only option is Linear PCM. For Output Track 1 I chose "Bus 1 (7.1)".

For the Quicktime MOV, I also used Linear PCM with Output Track 1 = "Bus 1 (7.1)".

The reason I thought I knew which channel was which, is because when I set up the 7.1 bus, Resolve automatically grouped and labeled the audio tracks on my Edit page. A1 says L, A2 says R, A3 says C, etc. So I assumed any output formats would know which channel is meant to be which, because they're all linked and labeled automatically.

The audio on my timeline track "A1 L" is indeed front left. The audio on my timeline track "A7 Lsr" is actually front center when played in the theatre, though. This is what confuses me.

I can make the render sound great in the theatre, but I have to disregard Resolves labels and order my audio as: L, R, L (again), R (again), Lsr, Rsr, C, LFE. (There is no way to make audio actually go to Ls and Rs, as far as I can tell.)

I've attached a screenshot and marked the specific pieces I'm talking about.
I added the on-screen text to keep track of which audio plays through which speaker when I play my render in the theatre.

Thank you again for your replies. I suspect there is some fundamental stuff I don't understand about what I'm doing, so I greatly appreciate your help as I try to make sense of all this. Perhaps I should just ignore the labels Resolve automatically put on the tracks, if different export options will simply be juggling the channel order around anyway? I just want to make sure I know the audio I put on a track will come out of the speaker I expect it to, when I send my export to a theatre.

I don't see those DS/ISDF/SDDS values anywhere

With a Kakadu JPEG 2000 Codec preference, the Audio tab exposes a Configuration drop-down which includes the various DS/ISDCF/SDDS values. This applies both to 17.4.6 and the version 18 betas.

The audio on my timeline track "A1 L" is indeed front left. The audio on my timeline track "A7 Lsr" is actually front center when played in the theatre, though. This is what confuses me.

By which method is the deliverable QC'd outside of auditioning in the theatre? EasyDCP Player or similar?