Did something change with audio analysis?

Anything and everything to do with DCP-o-matic.
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Joined: Fri Nov 29, 2019 11:07 pm

Did something change with audio analysis?

Post by dillonjamescole » Thu Feb 06, 2020 9:33 pm

I have used DCP-o-matic to convert dozens of .mkv files ripped from Blu-rays over the years. Anytime in the past I've analyzed the audio from one of these files, I never had a the True Peak line be red to warn me the audio was too loud.

But, today I'm trying to demonstrate to a local filmmaker where his audio levels should be in a film he's working on. The film is in 5.1. I'm using DCP-o-matic to analyze the audio from several different .mkv files ripped from Blu-rays to give him a visual example of what professionally mastered levels look like before his next test screening and they're all showing the true peak as being a lot higher than I thought they would be - true peaks louder than -3dB. I've looked at the audio from Blu-ray rips of The Lighthouse, Coco, Groundhog Day, Labyrinth, and a couple others to make sure I had good variation in genre. But after analysis, the true peak is always louder than -3dB. I don't remember it being this way using previous versions of DCP-o-matic.

Does that seem right? Maybe I'm just misremembering, but I could've sworn that most of the center track would hang out around -10dB for most of the feature.

I'm using program version 2.14.23. 2018 15" MacBook Pro - 2.4GHz i7 6-core processor.

Thanks for any help!

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Re: Did something change with audio analysis?

Post by Carsten » Fri Feb 07, 2020 12:22 am

Hmm. What would be wrong with TP hitting -3dB (or even 0dB)? I understand you haven't seen this before with your selection of content, but there is no legal requirement for leveling this kind of material. I have seen TP slightly above the 0dB line, and even that is perfectly legal.
Keep in mind, neither sample peak nor true peak is a an actual indicator for program loudness. RMS or LUFS is a much better indicator.
The red color in DCP-o-matic does not indicate an actual problem. Only clipped signals are an issue. The red color only indicates that one should probably have a look before you start conversion.

That said, I don't know if Carl changed something in the code that would result in different TP levels between earlier and current versions. I can easily check it, though, as I have many different previous versions installed on my machine. I do remember though that Carl and I negotiated about the threshold levels where the colors yellow and red would appear, but that would not have changed anything about the actual numbers.

This is the analysis of the Bluray 'Cheyenne - This Must Be The Place', which is not actually known as a 'loud' movie.
As you can see, the overall LUFS value of -28dB indicates rather low loudness. Yet, TP is at -1.65dB. DCP-o-matic 2.14.25

Bildschirmfoto 2020-02-07 um 01.27.54.png
Bildschirmfoto 2020-02-07 um 01.27.54.png (172.88 KiB) Viewed 113 times
This second screenshot is from a dialog-driven arthouse movie, again, Bluray. Note TP hitting -0.04dB, close to max.

Bildschirmfoto 2020-02-07 um 01.39.48.png
Bildschirmfoto 2020-02-07 um 01.39.48.png (161.94 KiB) Viewed 110 times
I tested both files with DCP-o-matic 2.10.5 and 2.14.25, and the values are identical.

- Carsten

Posts: 5
Joined: Fri Nov 29, 2019 11:07 pm

Re: Did something change with audio analysis?

Post by dillonjamescole » Fri Feb 07, 2020 4:22 pm


Your reply has provided excellent insight. Thank you very much!


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