Audio Levels

Anything and everything to do with DCP-o-matic.
funkytwig
Posts: 68
Joined: Mon Jul 28, 2014 9:37 am

Audio Levels

Post by funkytwig »

Is there a manual page that explaing how to set levels in audio. I have been useing the peak level and trying to get it to be black (not orange or red). My understaning is if the Peak is below 0 you are OK but I tend to nudge the level down so it goes from orange to black.

This seems to work, when get it black to black I sometimes try going up a bit and then maybe go back to the level that was black and this time it is Orange. Same number causing diferent colours. Exacly the same level types in. This is very fustrating. So what range am i aiming for. -2 to -4 maybe.

Also what LUFS should I aim for, what is the relasionship.

TL;DR

What True/sample peak should I aim for.

What LUFS should I aim for.

What Prak is too high/low. Same question for LUFS.

Ben
Carsten
Posts: 2668
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Audio Levels

Post by Carsten »

You can go up to 0dB Peak/True Peak. Peak doesn't really matter, as long as it doesn't clip. So, Red is still okay. Just stay slightly below 0dB. The color is just a warning indicator against clipping issues. It does not indicate a proper level.

RMS and LUFS/LEQ is much more useful, as these actually represent perceived loudness. No, single numbers can not tell you how loud your piece SHOULD be. Only you, or, the mixer, or director can decide about the proper loudness. But, for typical material, LUFS and LEQ will make sure you are in the right ball park and stay below or only close to complaint level.

An easy to remember LUFS value is -20 LUFS, or 80dB LEQ. These will not always be the right level, but they make sure no ears are bleeding, and dialog will be still intelligible.

To give you an idea about number relations: -15 LUFS or around 85dB LEQ would be VERY loud. This is a typical level to which action movie trailers are mixed.

I wrote a few more things here:

https://dcpomatic.com/forum/viewtopic.p ... 3576#p3576
funkytwig
Posts: 68
Joined: Mon Jul 28, 2014 9:37 am

Re: Audio Levels

Post by funkytwig »

Thanks for this. From my perspective as someone who has done a fair amount of DCP projections DCPs are a bit all over the place so you always need to have a listen at a few places. Generally, the music at the end is the loudest but not always so setting the levels in a cinema is a bit of a nightmare.

Would be good to have guidelines about max/min RMS and LUF & /LEQ and possibly a button to set them as what seems like a good level. Specificaly guidelines when these numbers are almost probably too big/small.

You mention in the post 'while typical LUFS numbers are in the range -15 to -30' but the DCP I am working on gives me LUFS -38 with a gain of 0 (true pead -1.15) and a gain of -15 LUFS is -48 (true pead -16). To stop anything going red/orange I need to do around -4 (LUFS -37, True Peak -5). Non of this is in the -15 to -30 range.

My gut feeling is to try to get everything black and have a true peak around -5, which is what the black seems to be (on the one I am looking at at the moment). I also feel that going greater than -8DB is probably not a good idea for the reason I mentioned in the next sentence.

In terms of my experience as a projectionist, the worst thing is having a too low level as the fader is logarithmic so getting it loud enough can be tricky. Alough obviously peaking is VERRY bad.

For setup the timecode where the longest bit (both a short peak and a loud bit that is, say a second) would be very useful. That way the projectonist can go to these time codes and check.

Maybe giving 3 loudest bits would be ideal. I would write this on the outside of DCP/let the projectionist know.
Carsten
Posts: 2668
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Audio Levels

Post by Carsten »

It always depends on your material. If you have audio that has not seen compression or professional mixing, you will always end up with some peaks already approaching 0dB, while your RMS or loudness is way to low. This also happens often with stereo mixes.

Can you show us the audio level plot of your DCP? Again - peak alone is completely irrelevant for loudness. It's no problem to go close to 0/red, as long as you stay away from the 0dB true peak mark (only multiple consecutive samples hitting zero actually mean 'clipping'). I have seen many commercial DCPs hitting a true peak of exactly zero. That is what someone should always aim for to maximise dynamic range. RMS/loudness really is what expresses perceived loudness.