How does the level measurement work with Dolby Atmos (Renderer/SuperVision)?

I have searched the forum, but it seems that no one has asked this question yet. (But maybe everyone knows but me.) I would like to understand how the Atmos renderer and SuperVison built into Nundeo measures volume/level. Are there any fixed standards there? Normally with Dolby Atmos, loudness and volume are measured based on a 5.1 downmix. (DEE and DME do it this way, for example.) But how does this work with Nuendo?

I also ask because we noticed some oddities when leveling in. Apparently the renderer has a limiter built in to prevent the signal from going off scale. I can still keep up with that far.
But, for example, exactly how and when the signal is cut off is not entirely clear to me. Sometimes I can’t understand why a certain level value is displayed for a channel in SuperVison or Halo Vision, for example. Because this value often has nothing to do with the final result (for example in the Dolby Reference Player).

We have collected some results, which I can’t publish right now, because I don’t have the time.
But I will be glad to publish them if needed.

I am looking forward to new findings. :+1:

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I’m very interested in this also. This post by Mark Ayres suggests the internal renderer take it’s loudness from the 5.1.4 downmix? Trim and Downmix Editor (Dolby Atmos) Bug?

Either way, this is certainly the biggest topic that needs clarification for me. Also, while I’m here - I think it would be nice if after the ADM has been rendered, Nuendo could display a ‘loudness summary’ report? Or at least the loudness readings not to reset after export… Just for final piece of mind that loudness is within spec…

Bruce

Yes, the loudness measurement is taken from an internal 5.1 down mix (not 5.1.4; I have corrected my original post).

There is a specific internal loudness re-render bus in the Renderer for this purpose. From the manual:

Using the 5.1 loudness re-render for loudness measurement

Use the 5.1 loudness re-render for loudness measurement during postproduction. Ensure that content meets delivery specifications by returning content to your chosen DAW, using the your chosen method and loudness measurement plug-in. The loudness measurement display in the Renderer is also fed from this loudness re-render bus.

This means that if you change your downmix settings in the renderer (for instance set the surround mix to 0dB rather than -3dB) your measured loudness will change, even if you have not altered the actual Atmos mix. This takes a few minutes to get your head around.

Loudness measurement is something that you need to factor into your workflow. Personally, I get it about right then (for an album) open everything in the Album Assembler and tweak it there in context.

Mark

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Can you please tell me where I can find this passage? I can’t find it in the manual for Nuendo nor in the manual for the (external) Dolby Atmos renderer. Thank you.

Dolby_Atmos_Renderer_Guide.pdf

Page 255, bang in the middle. It’s the last part of Section 20.1 Re-render output matrix.

M

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Hi Guys

Just resurrected this one as I’m still a little unsure how to manage loudness. I think I know, but I could do with clarification

When monitoring in 7.1.4 , the renderer is not monitoring ‘true’ loudness for delivery? In order to do this, we have to set the downmix to 5.1 and manage it from there?

I have my surround trim set to 0.0db - for my current project, integrated loudness is measured the same between 5.1 and 7.14 in the renderer. However, TP is out of spec in 5.1 but well within spec in 7.1.4.

I wonder if there is a more efficient way for Nuendo to monitor loudness for delivery? If Dolby spec states that the 5.1 downmix governs the loudness, it would be nice to have an option to always display that in the renderer loudness measurement display, even when monitoring in 7.1.4?

You don’t have to “set the downmix to 5.1” - the renderer automatically monitors an internal downmix for loudness measurement. Though I am not sure why you are seeing a change in the TP measurement.

ah that IS interesting. There is definitely a discrepancy with the TP measurement then. The truth is I had a mix rejected because the TP was +0.2db. This really surprised me as I am always very careful to be within spec. I checked the project again and couldn’t replicate it, TP was well within spec. I then ran it through 5.1 downmix and the TPT jumped to +0.17db. The only other thing I have set is ‘direct render’ for 5.1 downmix.

I’ll do some more tests and try and do a screen recording to prove it.

OK I’ve isolated a short section of the song where the TP occurs and ran a direct comparison in 7.1.4 and 5.1. Both return with different loudness measurements. 5.1 has a TP of +0.17 and 7.14 a TP of -1.57. I can only think I must be doing something wrong here somewhere…

5.1:

7.1.4

Interesting and not what we want to happen! I have no solution but would love to learn about it.

“the only other thing I have set is ‘direct render’ for 5.1 downmix.”
I’m not sure what this is, I can’t find the setting for it as well. Any hints?

thanks

If you go to the ‘ADM Authoring’ window, click the settings down arrow and select ‘trim and downmix editor’. There you can change these settings. Most submission specs I’ve been given ask for these two settings (0db trim and 5.1 downmix set to ‘direct render’):

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Just to be a bit clearer as the screen shots in my earlier post were a bit small and I failed to allow for the FX tails. Here are the two loudness measurements more accurately tested, showing identical results apart from the TP.
5.1:
image
7.1.4
image

Although I’m not sure how this relates to the internal renderer but usin a dolby renderer it’s almost impossible to not get TP overs on the fold downs of a loud mix with many objects.

I tried what peak level we had to reduce our bed and object limiters to for that not to happen and it was like -10…

The Dolby recommendation is/was to limit post downmix which is simple but really stupid as any actual overs can’t be dealt with properly that way. The Atmos downmix modules really needs built in TP limiting.

Thanks for bringing this topic up again @bsoord . I had already forgotten about it. :blush:
What I can say: The display in the Atmos renderer is not reliable under certain circumstances. (And the level meters are almost useless already because of their small size.)

Unfortunately, I haven’t had the time to test it in detail yet.

These settings only refer to the metadata and are taken into account by the Dolby encoders, for example. But not by Nuendo during playback.

Hi Guys
Apologies for resurrecting this thread. I am relatively new to mixing in Atmos and am noticing a difference in the readings from Supervision/control room loudness and the renderer loudness. I am mainly looking at the LUFS here.
Problem replicable on Cubase and Nuendo, Windows and Mac.

Control room and Supervision (inserted on the master output after the renderer) always show the exact same levels. The renderer always shows a lower reading between 0.2 and 0.9 LUFS.
If I import the ADM in the Album Assembler the readings match the renderer not the control room/supervision.

What can I do to get Supervision/Control Room meters to match the renderer, as I find those meters much bigger and easier to read, but if I cannot trust them that’s a problem.

Thanks

I wonder if adjusting the settings from 7.1.4 to 5.1 would get the readings to be closer? Total guess, but I know that Dolby mentions 5.1 re-render readings for loudness analysis, and in pro tools there is also a 5.1 loudness input provided to be used with external plugins and the internal renderer: https://professionalsupport.dolby.com/s/article/What-is-the-difference-between-the-Loudness-Re-Render-and-5-1-Re-render?language=en_US

You could also try to switch the Supervision module to “Loudness Netflix” instead. I think that one is dialog-gated. Perhaps that’ll make a difference (though I see that the renderer has both gated and ‘regular’ listed).