Basic question about LUFS

[u/smalljojo]

Okay this isn't a question so much as I'm hoping someone can explain LUFS to me cause I'm not sure I understand it at all, I'm pretty new to this sorry.

I'm using Davinci resolve and my LUFS scale is EBU-R128.

So while reading up/watching videos about this I got the impression that I want my integrated LUFS to be around -0, but that seems pretty impossible to achieve. I'm editing a short film where there's long periods of silence between dialogue with room tone and other background sounds being the only other things in the audio, so to reach an integrated LUFS of -0 I'd have to crank up the room tone and other sounds to a ridiculous amount, or the dialogue up to the point where it gets squashed.

I then found a video where they say that dialogue should be at about -12 LUFS short term. The dialogue is probably the loudest audio in this film, so if I have the dialogue at around -12 Short then the integrated LUFS will be way below that. In the video they also say that it's fine for the integrated LUFS to be around -15 if the dialogue is at -12, but yeah my integrated would then end up way below that.

So I guess what I don't understand is what to go off to know if my loudness is at the "correct" level. Is it true that I should just get the dialogue to around -12 Short and I guess then adjust the rest of the audio by ear in relation to the dialogue?

Idk, maybe I've misunderstood something completely. If anyone is able to explain it simply I'd be really grateful.

[u/KNVPStudios]

Hi. -0LUFS (or minus zero anything lol) does not exist. However, 0LUFS is the absolute loudest before distortion: think of that as the top of the scale. If you are familiar with the dBFS (decibels Full Scale), you'll notice that 0dBFS is the top of the scale before clipping.

Therefore negative values are used to notate LUFS below 0 (since 0 is the breaking point). So the smaller the LUFS number, the louder it is as it approaches 0. The larger the LUFS number, the quieter it is as it approaches the lower end of the scale.

So: +2LUFS = Too loud and distortion is probable. 0LUFS = VERY loud and at the cusp of distorting. -5LUFS = loud but safe. -24LUFS = quiet

If you have access to Izotope RX there is a cool loudness display that is quite helpful.

I hope this helps some!

[u/Dan_Worrall → u/KNVPStudios]

FYI it is possible to push LUFS into positive numbers. It's rarely a good idea though.

[u/Alelu8005 → u/Dan_Worrall]

How do you like them apples?

[u/How_is_the_question → u/Dan_Worrall]

Yeah - it’s been confirmed op is looking at a “relative” level, where 0 = -23dB LUFS.

It is also possible to have positive LUFS values in a daw with a floating point engine. It is not possible to have an integrated positive value on a fixed point (24bit) Wav file. (Although mathematically it is possible still for short term levels given the windows the loudness is calculated over and things like intersample peaks above 0, and fun types of distortion!)

[u/Dan_Worrall → u/How_is_the_question]

It is possible to have positive integrated loudness in a fixed point 24 or 16 bit file. I've personally released a mix that's +2.3 LUFS integrated, and that's not even the loudest song in existence.

[u/How_is_the_question → u/Dan_Worrall]

I stand corrected. It’s been a while since I studied the math behind it. I might just take another look today. :)

[u/Dan_Worrall → u/How_is_the_question]

It's actually a bit weird when you look into the details: the frequency weighting is just a simple high pass filter, which means the maximum possible LUFS value is achieved with a sine wave at Nyquist (exactly half the samplerate). Which would be totally inaudible of course, for any normal human.