Unable to Create DCPs in Anything Other than L&R Channels

Anything and everything to do with DCP-o-matic.
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RDOCINEMA
Posts: 1
Joined: Thu Jan 02, 2020 3:33 pm

Unable to Create DCPs in Anything Other than L&R Channels

Post by RDOCINEMA »

I'm new at this and I've tried looking through and reading previous posts about how to do 5.1 or 7.1 output for DCP creation on these forums but I've been unable to replicate others successes at all.

My problem comes very quickly on when trying to create a DCP film file using DCP-o-matic. I'm given video files from filmmakers and studios in many different formats but most frequently as .mov or .mp4. However, whenever I input this file into the software to create a DCP I'm ALWAYS given this displayed in the 'Audio' tab: Image

If the photo doesn't show, the problem is it ALWAYS only shows 'Content eng (aa' and ONLY has the L & R boxes checked green, with the other boxes going out for C, LFE, LS, & RS. But there are only two rows and if I check mark any of those other boxes it's just the same L & R audio that just comes out the other speakers and creates this awful echo in the theater.

Again, I'm sure this has been spoken about, but I've been unable to find any way to get it to display more options in the 'Audio' tab, no matter what kind of file I try to use. Any help would be greatly appreciated.

Carsten
Posts: 1604
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Unable to Create DCPs in Anything Other than L&R Channels

Post by Carsten »

I guess the files you receive for DCP conversion are plain stereo. So, that is what you see in the audio matrix. Creating surround audio or a center mix is usually only done by professionals, or very advanced amateurs. If all you get is stereo, it usually doesn't make much sense to try and create a surround sound DCP from it. You may give the Mid/Side Decoder a try though (under DCP->Audio). Or the Upmixer A and B (but be careful with them).

A file containing surround sound will usually come out like this (for interlaved multichannel):
Bildschirmfoto 2020-01-03 um 05.33.04.png
Bildschirmfoto 2020-01-03 um 05.33.04.png (18.16 KiB) Viewed 965 times
If you don't see input channels 1:3 to 1:6, your source file is plain stereo.


Maybe you can show us some more examples. It get's a bit more difficult if you receive the audio in separate files.


- Carsten

jproductions1
Posts: 1
Joined: Tue Jan 14, 2020 6:34 pm

Re: Unable to Create DCPs in Anything Other than L&R Channels

Post by jproductions1 »

Hi Carsten,

Reading your response and I have the same issue. I only have 2 channels of audio L,R but was thinking about using the upmix. Why are saying to be careful when using them? Is a mid/side decode safer?

Also my source file for the audio was turned up during a conversion to make it louder. When building a DCP it suggested to turn down the gain, so I did until the hint was not there. When I tested the DCP in a theatre the sound was lower than I would have liked. I made a Blu-ray from the source file and also played in a theatre and it was louder than the DCP just made. If I don't adjust the gain will it messed up the audio output in the DCP?

Last what does signed box stand for in DCP?

Carsten
Posts: 1604
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Unable to Create DCPs in Anything Other than L&R Channels

Post by Carsten »

The UpmixerA and B are experimental. You definitely need to listen to the DCP in a cinema in order to verify the result. Some material comes out strange. The Mid/Side decoder only covers the front channels and is more predictable. While in general, it is advisable to route dialog to the center channel, and e.g. music to L/R, it is technically okay to play stereo in a cinema. This is common for festivals and low to mid-budget advertising. The Mid/Side decoder usually does a nice job spreading a typical stereo mix to L/R and center.

I have found the advanced audio analysis (EBU R128/LUFS) value to be a useful tool to check loudness for a cinema presentation.

A LUFS value of around -19 to -20 should be okay for 'typical' material. -16 to -18 is bit more on the loud side, and above -21 (actually, lower than -21, as it is a negative value) is on the soft side. Nothing being wrong with loud or soft - it depends on the intention. Very often, cinemas adjust volume between preshow and main feature, so, it also depends a bit on wether your DCP will be played as preshow or main content. The LUFS value is the same unit category as the gain +/- adjustment, so, if your current LUFS value is e.g. -15 (probably too loud), try to apply a negative gain of -4dB to bring it to around -19 LUFS. These numbers are not scientific - they should get you into the right ballpark.

If you use the Mid/Side decoders or Upmixers, make sure you select 5.1 under DCP/Audio, and check the loudness/volume under DCP->Audio->show audio, since the upmixed audio level is not considered under the 'Content' ->'Audio' tab.

The 'Signed' checkbox covers a formal aspect only. It makes it possible to detect wether a genuine DCP has been modified. It is like putting a fingerprint or signature on the DCP. In a standard installation, the signature is a random one pointing to your specific DCP-o-matic installation, but since this is not a publicly available signature, in practice, it can only be traced to 'some' DCP-o-matic installation.


- Carsten

bmpte
Posts: 1
Joined: Sun Jan 26, 2020 4:18 pm

Re: Unable to Create DCPs in Anything Other than L&R Channels

Post by bmpte »

...and, btw. when I convert from stereo to DCP and I want "effect" (like trailers with megabass) ;) then:
L R C LFE Ls Rs
-12 off -16 0 -6 off
off -12 -16 0 off -6

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