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Automatic Gain Compensation

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Re: Automatic Gain Compensation

Postby enriquesilveti » Sat Jan 02, 2016 7:07 pm

Same information from EBU r-128 tour with Florian from EBU and Thomas from TC Electronic.

Go http://www.tcelectronic.com/loudness/li ... -glossary/

We use tb-ebuloudness plug-in (http://www.toneboosters.com/tb-ebuloudness/) + RX5 and LC2n.
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Re: Automatic Gain Compensation

Postby RJHollins » Sat Jan 02, 2016 7:44 pm

Should we not distinguish a difference in 'apparent loudness' and the measurement of level [voltage] sent IN/OUT of a piece of hardware or plugin ?

A plug-in chain needs to be mindful of 'gain structure' [UNITY gain] ... what goes IN = What goes OUT. HOWEVER, internal to the plugin or hardware, we can run levels hot/cold/neutral.

This has nothing to do with 'perceived volume'.

2nd:
Automatic Gain Compensation [AGC] can be most useful. HOWEVER ... isn't there always one :roll:
A string of FX in a chain, each with AGC function, can create a level nightmare. Each plugin is trying to adapt to the output of the plug ahead of it. As the prior plug makes level changes, each following plugin is having to re-calibrate its output ... which then feeds the next plugin ... and so forth.

Then it's decided to make a change in the plugin settings, order, bypass ... whatever.

3. Consider this scenario of active AGC while RENDERING a track :o

Back in the pure analogue daze, we had a signal generator [built into console] used to generate cal tones [sine]. Also included Pink/WHITE noise.

I've been working/testing a calibration idea/technique that would provide a PRACTICAL, working solution. Using standard tools [plugs] ... still requires manual adjustment. There are plenty of variables that can influence the results [thus the testing continues], but the goal is to find a faster technique to balance a FXChain that does NOT require playing the track from start to finish. Those who run 24+ tracks understand well .... even a single stereo track for mastering can be a time consuming process.

I'm always looking for improved ways. I can confirm that this cal technique has generally worked well ... and the sonic IMPROVEMENT through a balanced chain is much noticed :mrgreen:
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Re: Automatic Gain Compensation

Postby Mannymac » Sat Jan 02, 2016 8:43 pm

Absolutely agree with you RJHollins!I would be hugely interested in hearing more about your calibration technique

One way to speed up the whole "running through" process could be in some cases/DAWS to bounce down your song to disc, which will also make the plugin go through the entire song.
Hugely depends on whatever processing you have switched on by the time you are doing this of course.
You can then delete the bounced file because you don't need it oviously.
Hope this makes some sense ;)


What I have found though is that gain staging is not talked about enough especially with people my age (I'm 25).
Most of us young ones do not yet fully understand concepts like headroom etc.
Look at the countless internet threads of people asking where that "beeping,high putched" noise comes from when going into Nebula on all the forums to proof my point.
So anything that helps people to understand gain staging etc is a good thing imho. ;)
To me any Automatic Gain control can be a useful tool for quick and dirty level setting on a single track especially before going INTO whatever chain of plugins they have. Especially with software that so closely models analog gear like the AA tools.

(Or the Softube CL1B, which is calibrated for -18dbfs as well for example.)

Now most plugins have an output knob so of course compensating for whatever gain increase or decrease your processing has caused must still be done. :mrgreen:
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Re: Automatic Gain Compensation

Postby wagz » Sun Jan 03, 2016 1:43 am

enriquesilveti wrote:
wagz wrote:I have another request. Please, add automatic gain compensation to Nebula. That would save me so much time. Thanks.


Perception of loudness is unique to each person, for that reason was developed ITU 1770. So we can add a auto gain feature that will work only for the developer/tester but not for any one and that is the reason a lot for people complain about ITU 1770 normallization.


I think that I understand your point. It makes sense. I agree with you that perception of loudness varies from one individual to another. That kind of brings me back to my other request (for numerical entry on the output knobs...or higher resolution), though. I'm not having much fun trying to balance these Nebula knobs to match the IN/OUTPUT levels.

Still, I wouldn't mind an AGC feature using some sort of standard of loudness measurement, if there is such a thing, as a starting point. It would be fine, as long as there was still a high resolution output knob...for whenever I choose to ignore what the meter says.
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Re: Automatic Gain Compensation

Postby wagz » Sun Jan 03, 2016 1:44 am

Mannymac wrote:If you want to dive deeper ito this (to me very interesting) topic of loudness and gain staging I can also recommend this brilliant article by SoundOnSound magazine

http://www.soundonsound.com/sos/feb14/a ... ss-war.htm

You need to buy the PDF for full access if you are not a subscriber which will only cost you 1,5€ or so.
It really is worth it.

For a budget friendly LUFS meter with great functionality check out
https://www.klangfreund.com/lufsmeter/

Brilliant measurement plugin with great extra functions.


Thanks, Mannymac. I'm gonna check into those. I think that there may be an LUFS meter built into my DAW. I'm going to try that thing out.
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Re: Automatic Gain Compensation

Postby RJHollins » Sun Jan 03, 2016 2:00 am

remember:

The [SHIFT]-key with Left-Mouse button allow fine adjustment setting.
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Re: Automatic Gain Compensation

Postby wagz » Sun Jan 03, 2016 2:02 am

RJHollins, I would also like to hear any info you are willing to share on streamlining the process of calibrating the chain.

Originally, I brought up this AGC thing because I wanted to ensure that the level that left each plugin (in this case, Nebula) was the same as what entered it. enriquesilveti brought up a good point, which was basically: What would be used as the standard of measurement for the AGC? I don't know the answer to that. I have just been using VU and peak meters (dBfs)to match levels.

I only know that I want things to operate easier and more efficiently. Any suggestions are welcome. I brought up a similar question with another well known mixer. He told me to mix with my heart, not my brain. LOL. I should definitely follow his advise.
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Re: Automatic Gain Compensation

Postby wagz » Sun Jan 03, 2016 2:17 am

RJHollins wrote:remember:

The [SHIFT]-key with Left-Mouse button allow fine adjustment setting.


Hmmm. I tried that. Nearly every DAW and plugin that I use operates that way. So, I'm used to adjusting the knobs that way. I still had a hard time dialing in the settings that I wanted with Nebula.
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Re: Automatic Gain Compensation

Postby RJHollins » Sun Jan 03, 2016 6:54 am

wagz wrote:RJHollins, I would also like to hear any info you are willing to share on streamlining the process of calibrating the chain.

Originally, I brought up this AGC thing because I wanted to ensure that the level that left each plugin (in this case, Nebula) was the same as what entered it. enriquesilveti brought up a good point, which was basically: What would be used as the standard of measurement for the AGC? I don't know the answer to that. I have just been using VU and peak meters (dBfs)to match levels.

I only know that I want things to operate easier and more efficiently. Any suggestions are welcome. I brought up a similar question with another well known mixer. He told me to mix with my heart, not my brain. LOL. I should definitely follow his advise.


I'm willing to open dialog/conversation toward a Gain Staging solution, and happy to share the concept I'm working on.

To begin ... There are several approaches. Each with pros/cons. Also, are dealing with 1 or 2 plugins ... or maybe a dozen or 2 ?!?

I look at the larger chains as a good challenge to balance. Let's remember, if we are using a NEBULA equalizer, it can easily take 6 instances ... H/L Shelfs with 4 bands. Throw a Console IN/OUT, maybe TAPE, extra color Pre-Amp, and some compression. There ... easy to get a list without trying.

Being VST's in a chain, of course, we don't have the screen real estate to easily see all these plugs, let alone adjust INs/OUTs.

What we deal with.

Slap an EQ on a track, crank or cut the gain of a band [shelf/bell] ... the OUTPUT level is gonna change. That change will impact every following plugin in the chain.

What get's impacted ... forget LEVEL ... it's the HARMONIC content that changes. [Nebula is DYNAMIC .... that's why we LOVES it].

However, that LOVE can mess with us.

I'm speaking of IN-ADvertant level driving into the next plugin will influence our evaluation of the track. Course, we could BYPASS all following efx ... but we knock our short-term REFERENCE out.

2nd problem happening ... we are changing a overall track volume level. Whether UP or DOWN, it CAN impact how we hear the track.

There are some useful utilities out there. 1). PERCEPTION, and 2). the free A/B JS routines from TB Audio for REAPER. I use both.
They are 2-part plugins. One at the TOP of the chain, the other at the point of measurement interest [or the end of chain ... depends].

Another useful plug is HORNET. At the TOP of the chain, it can gain stage it for [my typical] -18dB. Playing the track all the way through ... I see the final gain value, and then I pull in KLANGHELM's VU and insert after HORNET, adjusting its VU TRIM based on Hornets read. I then pull Hornet.

KLANHELM's VU are my personal choice for analogue VU meters. The ballistics are as true to hardware as I'd ever want or remember, the meters can be cal'd for any operating level, AND, it has a built in TRIM with option PEAK numeric readout and needle HOLD. It cost 9 bucks :shock:

... more to come.
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Re: Automatic Gain Compensation

Postby wagz » Sun Jan 03, 2016 7:14 am

RJHollins, are you saying that you do or do not try to maintain 0 VU when going from one part of the chain to the other? I try to maintain it not matter how many programs I run in the chain.
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