DCP with 7.1

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Vsevolod
Posts: 7
Joined: Mon Mar 04, 2019 7:37 am

DCP with 7.1

Post by Vsevolod » Fri Mar 15, 2019 2:52 pm

Hello! I will have the first experience with showing my movie in the cinema and thank your program! Many people praise DCP-o-Matic!

I have a few questions:

1) The most important question: I mixed my movie in 5.1 and now the cinema gives the right to use the surround sound in 7.1. I use the DTS Neural upmix plugin to mix 5.1 to 7.1 for my own satisfaction. It looks like this:

Image

But when I load into DCP-o-Matic, the default option is 5.1. I switched in the settings to 8-5.1 / HI / VI. And now my channels look like this. Is this the correct channel order after using the up-mix plugin?

Image

2) Which format is better to use for DCP. I read that DNxHR 12bit. I can use it. Anything else?

3) Explain to me how the order of channels in the DCP in the cinema itself is established? Is there a danger if I use the standard LRCLFELsRs, and in the cinema it is installed: LRLsRsCLFE. Or any digital cinema and trailers come in the standard first version? What do I need to know in order not to be mistaken with this?

Thank you! :)

Carsten
Posts: 1161
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: DCP with 7.1

Post by Carsten » Tue Mar 19, 2019 5:30 pm

Hi,

I don't think an automatic upmix from 5.1 to 7.1 makes good use of separate backsurrounds. It may sound a little bit more 'vivid' for music or athmospheric sounds in the surrounds. On the other hand, it doesn't hurt, so...

To use 7.1, you need to setup the audio channel number to twelve, as BSL and BSR go to channels 11 and 12 (7-10 are left free, at least if you don't use HI/VI-N in 7+8). So, in the audio matrix, you will have a gap of 4 channels between Surround Right and BackSurroundLeft. 8 channels is for 5.1 +HI/VI-N.


It is no problem though, to play a 5.1 mix on a 7.1 system (it needs to be setup for 5.1 though, so the projectionist uses the 5.1 preset on the sound processor). Cinema sound processors will not 'upmix' 5.1 to 7.1 themselves, they will only play Left and Right surround through the back surround channels as well (which is different from what the DTS neural upmix plugin does).

If you set your DCP audio channels to 12 - 7.1+HI/VI-N (don't know how that comes out in your localization), you will see the proper channel labels and order beyond 5.1 in the audio matrix. All cinemas use the same DCP channel order you can see in the audio matrix.

If you work in Windows, DNxHR is probably your best choice. On a Mac, I would choose Prores.

- Carsten

Vsevolod
Posts: 7
Joined: Mon Mar 04, 2019 7:37 am

Re: DCP with 7.1

Post by Vsevolod » Thu Mar 21, 2019 12:58 pm

Thanks for the extended answer, Carsten!

It looks like that, right?

Image

Yesterday I successfully passed the test in the cinema! I compiled DCP thanks to DCP-o-Matic! And I really liked the sound of my mix. Thank you very much for the excellent program! :D

Image

I used DNxHD RGB 444 and tried different bit rates (125, 175, 240).

Please tell me which bitrate is best used for short films, so that there are no artifacts, different red, yellow lines and distorted text? Some argue that over 200 in budget cinemas may appear artifacts. Thanks!

Carsten
Posts: 1161
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: DCP with 7.1

Post by Carsten » Thu Mar 21, 2019 3:29 pm

Yup, Audiomatris is correct like this.

JPEG2000 as used in digital cinema has lot's of 'spare room' in the compression rate. There is a technical limit per spec at 250MBit/s, but, some dominant servers may already stutter or stop around that peak data rate. I usually set my installations to 230MBit/s in prefs and then never think about it again. This is not necessarily an average or typical datarate for your DCP - finally, your content complexity influences the actual datarate in the file.

When you look at commercial, even high budget mainstream DCPs, you rarely see the highest data rates - for what reason ever.

Note that the spec limit of 250MBIt/s is the same also for 4k or 3D (24/48fps).

The only reason to use lower settings like 150 MBit/s is if you want to save storage space or transmission bandwidth. E.g. if you could use a 16GB usb stick, and the first version comes out slightly larger. So, 150 to 230 MBit/s is usually okay, and real content will only rarely max out to these numbers.

More than 250MBit/s would only be useful for higher frame rate DCPs, but then you have to make sure for each and every location and screen wether the servers are capable of supporting that. This has nothing to do with Interop vs. SMPTE capability. There are many SMPTE compliant servers/projectors out there that will not support more than 240MBit/s and/or higher frame rates.


- Carsten

Vsevolod
Posts: 7
Joined: Mon Mar 04, 2019 7:37 am

Re: DCP with 7.1

Post by Vsevolod » Fri Mar 22, 2019 3:53 am

Thank you very much, Carsten! :D I will try to keep the bitrate within reason.

And the last question that interests me concerns this magic DCP software!

My film is divided into 6 short episodes of 5-7 minutes. Would it be right and safe to convert each episode in a new DCP? The disadvantage of this method is that projectionists can confuse the order of episodes.

Or can I convert 6 videos and 6 audio tracks in one DCP in the correct order? And is it possible with the help of DCP-o-Matic? If so, how? Thanks again!

Carsten
Posts: 1161
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: DCP with 7.1

Post by Carsten » Fri Mar 22, 2019 10:20 am

No problem:
Bildschirmfoto 2019-03-22 um 11.17.06.png
Bildschirmfoto 2019-03-22 um 11.17.06.png (171.76 KiB) Viewed 37 times
Projectionist will usually create a playlist where they can line up multiple DCPs for playout. Yes, if you're unlucky, they could mix the order.
So, if there is no reason to play any of your episodes out of order intentionally, just make a single DCP out of them.

- Carsten

Vsevolod
Posts: 7
Joined: Mon Mar 04, 2019 7:37 am

Re: DCP with 7.1

Post by Vsevolod » Fri Mar 22, 2019 12:42 pm

Thanks for the great help, Carsten! In my case, I have 6 separate audio tracks with 6 channels for each episode.

First I add "Episode1.mov - then the next track Episode1.wav, Episode2.mov -Episode2.wav and so on ... Do I understand you correctly?

Carsten
Posts: 1161
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: DCP with 7.1

Post by Carsten » Fri Mar 22, 2019 1:07 pm

You don't need to follow a specific order during import - you can arrange everything later in timeline view and under Timing/Trimming.

But, yes, it is a bit fiddly. I usually recommend to add composite video+audio files for that reason. Would be worse if you had split the 7.1 audio into 8 separate channel files as well. Are you sure your audio files sync up properly with the videos?

- Carsten

Vsevolod
Posts: 7
Joined: Mon Mar 04, 2019 7:37 am

Re: DCP with 7.1

Post by Vsevolod » Sat Mar 23, 2019 2:46 am

I appreciate you, Carsten! Yes, I performed the post audio stage on my own. This is my training project. Everything is very accurate and neatly synchronized. I separately export the video, and from another DAW audio track (PCM 6 channels). Perhaps I could merge them without re-encoding?

Can I set the video sequence (3-4sec) 16+ in the time and trimming window before each episode without affecting the video and audio?

Carsten
Posts: 1161
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: DCP with 7.1

Post by Carsten » Sat Mar 23, 2019 8:05 am

If the audio is coming from a separate process, and you are doing the final conversion yourself, there is probably no reason to reunite video and audio. Except you want to have another more common master format (like DNxHD with audio).

It's no problem to space audio and video to separate the episodes. Just alter the starting point for both video and audio by the same amount, if video and audio for each episode start exactly aligned. Empty spaces will be filled with black and silence automatically.

- Carsten

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