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For general discussion related FlowStone

Re: AGC to keep audio energy to some target level

Postby ElCuco » Sun May 24, 2015 8:23 pm

martinvicanek wrote:The original idea of the device was to avoid clipping, so it will only reduce, not increase volume automatically. I thought about adding a Reset button, but that would be the same as turning up the Volume knob which is already there. Would it make sense to add an option for automatic gain build-up at some (adjustable) rate like 0.1 dB per second? It would go on until it hits the limit, gain is reduced, starts to creep up again, and so on? Is there a better way?


https://www.youtube.com/watch?v=EJ7Pu93x_gk
A correct one need ACG + LIMITER

Your control level is nice martin but is slow, and not provide anyway to recover the volume :(
Again a correct system should target signal to some specific level, for sure preferred in LUFS not in dbfs
I love your example, you think is possible speedup the process?

idea of recover level at 01.db per second, is ultra slow.
About how prevent clip again, I think signal shoul be metered before apply any increase, in that way you not increase unlimited making audio clip again. Meter before make audio go up is needed.
That's work? What you think?
Can be done this with lufs not with dbsfs ?

And I think a compressor/limiter is needed for handle audio with that under little range.........but out of that range use your method for up and down the level.
I think something like this Frankestein work.

What you think?
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Re: AGC to keep audio energy to some target level

Postby ElCuco » Sun May 24, 2015 8:42 pm

Check this example, do veryell but sound really bad.
MMM I think should be some combination of this with your example.
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Re: AGC to keep audio energy to some target level

Postby MyCo » Sun May 24, 2015 9:35 pm

Just a classic AGC...
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Re: AGC to keep audio energy to some target level

Postby ElCuco » Mon May 25, 2015 11:37 am

Wow Myco, you construct this?
Is very accurate, super clean sound and soft work, is very good. :shock:

Anyway with AMP to 0db the audio clip.
And some times audio sound very distorted and I have to move the amp knob and that stop the distortion and back all to normal.
I testing this a lot, when this troubles not happen, wow is very good.
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Re: AGC to keep audio energy to some target level

Postby MyCo » Mon May 25, 2015 1:40 pm

The distortion could happen when the measured amplitude in the Envelope follower drops very low (the input is just above noise floor). In that case when a spike come in, it is amplified a lot more than necessary due to the attack time. You can look at the dB output in the attached schematic. When you hear the distortion, the readout should read very low.

BTW: when you want to try out a ridiculous advanced AGC, try this chrome plugin:
https://chrome.google.com/webstore/deta ... odgcoklfio
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Re: AGC to keep audio energy to some target level

Postby martinvicanek » Mon May 25, 2015 3:45 pm

Yes, MyCo, that's a better approach to AGC. There will be some slight distortion from the envelope follower ripples, noticeable for low frequency input at short attack/decay settings. Moreover, if you set target level to 0 dB it will clip because (1) the envelope follower does not quite measure the peak level and (2) clipping occurs at 0.99 not 1.0. But that's really only nitpicking, the schematic does its job well for reasonable settings.
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Re: AGC to keep audio energy to some target level

Postby ElCuco » Tue May 26, 2015 11:51 am

Myco you are right, that google plugin do the job in a perfect way, will be nice your AGC can do the same. :D a single knob or slider for adjust all.
Will be usefull for you the source code of that chrome extension?
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Re: AGC to keep audio energy to some target level

Postby MyCo » Tue May 26, 2015 5:37 pm

I've been working on the Chrome plugin, so I know the real source. However, I'm not allowed to talk about how it works...
BTW: The JavaScript source is pretty useless, as it is just compiler output.
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Re: AGC to keep audio energy to some target level

Postby ElCuco » Wed May 27, 2015 12:06 am

Oh!
Mmmm bad news, so we never see something working in similar way in Flowstone.............well not with my knowledge lol.
Myco, can do something for improve your FSM , please!
:mrgreen:
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Re: AGC to keep audio energy to some target level

Postby mrking » Sat May 30, 2015 10:54 pm

AGC, myco design is not correct, first -40 noisefloor is not used as standard, also adding -40 won't make any difference, also 0 dB doesn't make any sense????? just few over cpu cycles... If you ask me, you can try FOLDBACK waveform design with limiter, that's what your after, I don't think you probably understood AGC , when AGC used in MOBILE, ADVANCED CARS, Limiters are not used, AGC is actually automatically kind of LIMITER/EXPANDER.


I am into sound reinforcement business 25+ years of experience as manufacturer, advanced level technician, etc and I don't think you understand yourself what your asking. AGC is different it's kind Automatic Gain adjuster, but NOT NOISEFLOOR. GAIN is magnitude of power . Noisefloor is dynamic range. Hope you understood. Anyhow foldback with limiter, this way it won't clip as well limiter (up/down) will perfectly adjust It, use BRICKWALL for that purpose.



Myco make something this:
dBFS input detect values assume -80 dB. Automatic gain, in*(in^2). Rather sound clips limit gain, remember ur doubling power. Brickwall. So values dont exceed and limits automatically. That would be AGC
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