Peak and metering

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Alexandre Garacotche

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Peak and metering

PostFri Jul 13, 2018 2:03 pm

Hello,
I have something bizarre.
I have an audio file with a peak @ 0db (absolute 0). When put on a track in Davinci Resolve, it goes without any interaction (no change of volume, eq or whatsoever) into the master bus. I raised the master bus down to -5 (I assume it is db).
Then I exported wave 32bit.

I imported the resulted file into a daw and I noticed there, that the peak is still @0db !
So I have a couple of questions :
1) is track metering in db ? is the leveler in db too ? Does the 0 present on top each channel represent an absolute 0db or is that some kind of K-system which allow +5, or +10 db to go over the 0 (which then represents some kind of indicative threeshold) ?
2) is there some sort of channel sumup when going to the master.
3) is there some kind of normalizing at export time ? (which would then make sense)

Thanks.
Alex
Last edited by Alexandre Garacotche on Fri Jul 13, 2018 2:49 pm, edited 1 time in total.
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Alexandre Garacotche

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Re: Peak and metering

PostFri Jul 13, 2018 2:29 pm

I am editing my first post here.
I noticed that the track being at 0 (no change of volume), the master being raised down at -5, the view meter of the master still shows the peak going all the way up to the top. I need to raised the master down to -12 to see the peak @ around -2db.

That proves that the 0db of each individual channel is not absolute.
Maybe it is in the docs, I am looking at it now, but this is important to know.

Maybe there is a relation to the metering marks of the channel's view meter and the actual leveler ones, for which 0db is at around -10,2 db on the view meter.
Image

I doubt that but then we have no indication of how high our peaks are.
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Reynaud Venter

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Re: Peak and metering

PostFri Jul 13, 2018 3:22 pm

Generate a 1kHz sinusoidal tone referenced to 0dBFS with the Fairlight Oscillator.
Patch the Oscillator to a Mono Audio Track's input, and route the Mono Audio Track (A1) to a Mono Main Buss (M1).

The Source Mono Audio Track (A1) Fader will be at its default position of 0dB (as indicated by its associated 0.0 value), and the corresponding Channel Metering will represent the source signal's peak value as 0dBFS.

Reduce the Mono Main Buss (M1) fader by 5dB, resulting in its fader level reading being indicated as -5.0

The corresponding Mono Main Buss (M1) metering will represent the resulting signal's peak value as -5dBFS.

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Alexandre Garacotche

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Re: Peak and metering

PostMon Jul 16, 2018 7:49 am

Thank you Reynaud,
But what you are suggesting does not fix the initial problem, merely try to see if we have the same phenomena with a bus.
Nevermind.
Also I noticed another problem. I have a Stereo track and a mono track both going to the master, the master being @ -5db. when exporting a clip audio only to fix some pops into a DAW. The clip that is on the stereo track is raised down by 5db (normal because of the master reduction) BUT the clip on the mono track does not get the reduction.
I use Davinci Resolve 14. I have seen there is a lot of improvement being done on the 15, I will upgrade after this project and see if theses bugs has been fixed.
Thanks anyway.
Alex
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Charles Bennett

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Re: Peak and metering

PostMon Jul 16, 2018 11:48 am

The white mark where the fader sits does not relate to the meter scale. It is merely an indication of the unity gain point of the fader. At this point the volume of the audio is unchanged from the original file. With an oscillator on a mono track showing -10db and the pan centralised, the stereo master should show -13db on both legs as this takes into account the pan law which appears as a default of -3db. If you pan the oscillator track hard left or right you will see the the master legs rise to -10db.
The top of the meter scale is not 0vu it is 0dbfs. 0vu is normally around -14dbfs to -18dbfs in a DAW. 0dbfs is therefore +14vu to +18vu.
Rather than using the faders to give you a proper working level, use clip gain instead. There is no normalisation on export. As to the level not changing when rendering a track and bringing it back into Resolve, are you rendering using the individual clip option? If you are it uses the original clip audio not any changes you have made. This is normal.
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Alexandre Garacotche

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Re: Peak and metering

PostMon Jul 16, 2018 4:02 pm

Thank you for these precisions.

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