DCP for IMAX with 12.1 sound?

[bengedlow]

Just wondering if anyone has done a DCP for IMAX with the new 12.1 sound setup?

We're just finishing an IMAX film (shot in 4, 5 & 6K), designed to go through the new laser process, but we'd like to get a look at it in a regular IMAX theatre beforehand.

And it would be grand if we could do the DCP for the non-laser theatres right here in-house. Heard great things about DCP-o-matic.


Ben

[Carsten]

I can only assume that the IMAX 12.1 is a plain 14ch/16ch DCP. IMAX masters all their IMAX laser content on their own, so I don't know how to get a foot into a laser IMAX, bypassing their mastering service.

The normal (xenon) IMAX can play ordinary (2D) DCPs with 5.1 sound. Only 3D features need a special IMAX signature to play. I don't know if IMAX also restricts asset origin that way for their laser installations. I think that it would be wise to allow Laser IMAX systems to play standard DCI trailers. So at least if your content is unencrypted and 2D, I would simply try to contact a laser IMAX site and ask them to ingest and play it.

You could create a simple Test DCP with audio 16channels, with a voice speaking 'Channel 1', 'Channel2' etc. on each channel. That way you could easily find out the channel mapping. It is possible that IMAX 12.1 uses Auro 3D or some other encoding. But for now, I doubt it and assume it is plain 13 (14/16) channel LPCM in a standard MXF.


- Carsten

[scorpio81]

Two more things. Only one projector used when playing non-IMAX content. And for features that are 30 minutes or longer, a special announcement that you are watching a non-IMAX content is shown.

[bengedlow]

Thank you Carsten, very helpful,

Normally this outfit does all their post in a high end post prod studio, and the laser version will be done in LA. I've been encouraging them to do more in-house. I did a test color-grade of a short IMAX film last spring, using FCPX, and it was comparable (visually identical) to what they later got at a high end post prod. So this time round we did a whole film with FCPX. Seems to look pretty good.

Victor Sandrasagra at EyeSteel Film was quite enthusiastic about DCP-o-matic. Very. So I wondered if we couldn't take this little project further, and output at least a 'normal' IMAX DCP in-house. (Apparently the 'normal' IMAX DCP will play on the laser system, only not using the two projectors.)

The editor just told me they also have a 5.1 mix. If I do a straight 5.1 (set accordingly in DCP-o-matic) that's a universal format right?, so it should go out into the appropriate channels at any standard 5.1 theatre (read 'normal' IMAX in this case)?

And if I try a 12 channel setup (I think it's a 12.0 they are calling it, rather than a 12.1, my mistake), you recommend choosing the DCP-o-matic '14' channels? These are the identifiers on the 12 channels:

C
L
Lsr
Lss
R
Rsr
Rss
C
L
Ls
R
Rs

I wondering if there would be a way to set DCP-o-matic to best facilitate the audio output of the 12 channels?

All ears,

Ben

[Carsten]

The DCP-o-matic 'full channel count' identifiers are generic, they don't necessarily reflect the IMAX channel assignment. E.g. they contain common HI and VI-N identifiers, but these may not exist at all in IMAX (or other general) cinemas.

To give you an idea - all 'normal' digital cinemas nowadays are very transparent as far as their audio setup goes. You create a 5.1 mix and and it will play in every cinema in the world. Even if a smaller arthouse only has a single center speaker attached, it will still be, well, 'compatible'.

IMAX is a bit special. I have never seen any technical detail on their setups, I have never seen an IMAX projectionist talking on a forum about their internal doings. There is a lot of automation going on in IMAX cinemas, and I would expect a normal 5.1 mix to play okay, as they probably want to play standard trailers without special arrangements.

However, I have no idea wether you can simply create a straight 12.1 or 12.0 mix and expect it to play with proper channel assignment. Therefore, if you have access to an IMAX cinema, I would first create a test DCP, outnumbering all 16 DCP channels, and find out if/where those channels above channel 6 play...

It is possible that the 12.1/12.0 sound setup will only be active on IMAX signed CPLs, just as the 3D will not activate without an IMAX signed CPL. In that case, your test DCP would indicate only the first 6ch, and then may stay silent from 7 to 16.

- Carsten

[bengedlow]

You are an ace Carsten!

This is very helpful.

Ironically, the local laser theatre we are doing the try out in ... just got an email back: they don't have a projectionist anymore. ??? They have the laser setup, but no projectionists. This will be interesting.

I'll call the fellows who did the mix, do my homework, and report what I find out back here.

And because it's the new laser setup we are ultimately forced to send our film as a DPX or TIFF image sequence to LA. And exported out of FCPX the DPX is washed out (when brought into Resolve to check). I finally figured out how to set Resolve to read the ProRes4444XQ (amazing how little there is in the forums about this). But notice that a TIFF or PNG or JPEG image sequence from FCPX is 'darker' than the ProRes4444XQ when brought into Resolve. While the DPX image sequence is lighter. It's crazy time.

I'll be very happy to go back to my own films (non-IMAX) the moment I can deliver this show. Grrr.

Will report back on the IMAX setup for sound ... going to go with the 5.1 on the test, because I think you are bang on: they have to play trailers, and even standard fare Hollywood in a lot of those theatres.

[bengedlow]

This is

image001.jpg (11.75 KiB) Viewed 13205 times

This is the setup I got from an IMAX theatre. Apparently even they are having trouble figuring things out –– with the new laser projectors a lot of things are changing.

I'm wondering how one could reproduce this channel layout using DCP-o-matic ... or whether it's at all possible? This is what the tech said:

"I will try to get a look later but I think this is the channel distribution from top left to bottom right 1 to 12 and SubBass shoud be include in the Mix but I not 100% sure."

[carl]

You can just set 14 channels in DoM and send whatever you like to them. The names that DoM gives to those 14 are

L
R
C
Lfe
Ls
Rs
HI
VI
Lc
Rc
BsL
BsR
DBP
DBS

so your first 6 are the same then you have

DOM HI -> IMAX Upper Center
DOM VI -> IMAX Side Left
DOM Lc -> IMAX SIde Right
DOM Rc -> IMAX Top Front Left
DOM BsL -> IMAX Top Front Right
DOM BsR -> IMAX Top Rear Left
DOM DBP -> IMAX Top Rear RIght

If those IMAX channel names prove correct we could include them in DoM as an option.

[Carsten]

What they gave you is something like room layout, not the channel assignment. Now you may try to do a quick shot with real world audio and play it through their system - but I can tell you, it will be hard to find out wether your mapping is correct by simply sitting in the auditorium and listen to that audio.

Again - fire up an audio recorder app or your iPhone, count from 1 to 16, cut into single number slices, assign these 16 short audio snips 1:1 in DOMs audio matrix, loop this 50 times, and play in the IMAX auditorium. They may also have a sound processor in the booth with VU meters and their channel labels attached, so you may be able to use that for checking as well. You could try to follow their map, but I suspect it could be very confusing to verify it in their auditorium. But it may serve as a starting point. All depends on wether they give you a chance to play your test-content in their auditorium.


Now, we would be REALLY interested to know what comes out. It seems more people are doing work for IMAX, but those commissioning these jobs seem to be unable to supply the proper target formats or instructions.


Techwise, there could be different things happening:

The sound system is operated transparently beetween 5.1 and 12/13ch mode. No special switchover sequence. That would mean, the first 6 channels would need to follow the standard 5.1 arrangement and play to L/R/C/LFE/LS/RS in order to be compatible with standard 5.1 DCPs.
Then in 12/13ch, the 'non-standard' channels could follow.

However I don't think that's what IMAX is doing. They probably have a straight-through 12/13ch mapping to the speakers in your image, but do some cross- or upmixing to all speakers when they play 5.1 (probably with the exception of the TOP speakers). This is also to exclude unwanted feedthrough of tracks like HI/VI-N that may appear in standard DCI content. They do not want these to be audible, so they at least need to disable these channels (all above channel 6) when they play standard 5.1 content. But they may also have a 7.1 mode, as their speaker layout supports it.

Whatever, you need to get to the ground of it first, and that is by playing a suitable test file. Now even with the audible number counting, your ears will have a hard time to pinpoint the directional difference e.g. between Center-Top and Right-Top. So, first visit their booth and check wether they have any visual channel indicators there to help you. I still suspect you will only have access to their full 12/13 channel setup with an IMAX signed package. They may have set it up in a way that their 'system' is able to automatically detect the audio type and switch over their audio processor accordingly.

Again, get back to us with whatever details you get to know.

- Carsten

[scorpio81]

We have IMAX5 sound (5.1 setup) and the sound processor have no any channel indicators. I believe IMAX12 sound processors also have no any indicators.