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Offline Hanginon

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AGC
« on: May 27, 2014, 06:50:04 AM »
I've been using VDJ enough that I am now comfortable with almost all it's features. I'm a strict music only DJ (older adult music), so instead of using the Karaoke window, I run VDJ in classic mode and have a Windows Explorer file of my music opened in it's place. I use it for previewing and dragging/dropping songs to the playlines. Works excellent. It's really the same window VDJ uses to load individual files, but it is open all the time.

I try to produce the absolute best sound quality. I think the audio engine in VDJ is wonderful.

I've been using the AGC function with the default settings. Problem is, I really don't know how it works or if the settings have been optimized for Karaoke. "Like an FM radio station works" does not give me a warm fuzzy feeling since some produce horrific sound quality. Assuming I am always at my PC during my performance controlling the gain, could I get an even better sound with different settings? I freely admit the AGC might be smarter than me!

So, given all of that, how does it work? If it's operation is outside the scope of these discussions, could you please direct me to a place it is.




Offline Fabio

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Re: AGC
« Reply #1 on: May 27, 2014, 12:39:12 PM »
"Like an FM radio station works" is basically an analogy on the fact that radio stations usually have their signal turned up during the day because the sun limits their signal from propagating.  During the evening they turn it down because the sun is not there and the signal travels more easily.  Sometime if you happening to be listening to the station and they make the change abruptly, you can hear the difference in volume.  Most times you can't hear the difference...I suspect is because they make the change gradually.  The AGC is basically making the change for you...when you play a song that has certain frequencies that are too loud, it automatically brings them down to a more manageable level and conversely when some frequencies are too low, it brings them up...this helps to keep your volume levels at a certain range, the AGC has a top level and a lower level...anything that falls in the middle doesn't get changed.  It's only triggered when it goes above or below that range.  You can actually change it so that the range is smaller or larger but I find that works just fine at the default settings. This version of the AGC seems to work perfectly for me that I get complimented on my sound. On the previous version of VDJ, I had to make changes. By the way, this works regardless of whether you're playing regular mp3s or karaoke.  Basically the only difference is that you're have graphics...the AGC has no effect in the graphics.  FYI, it's not 100% effective so you still have to watch your volume levels...it's only an aid.  I found at times some songs are recorded at very high volumes that you still have to bring the volume level down...or they're recorded at very low volumes and you have to bring the volume up for those songs.  I suspect it's because the AGC is looking for certain frequencies not necessarily volume levels.   Still it works pretty well.  For example you can actually hear the difference in sound between VDJ and windows media...try pluging in headphones (you don't need to connect to your amp/mixer) to you laptop (or desktop) then play the same song via windows media player and then try it via VDJ...you should notice the difference. This is the AGC at work.


Fabio Q.
Shooting Star Karaoke

Offline Hanginon

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Re: AGC
« Reply #2 on: May 27, 2014, 03:33:28 PM »
I've been using the AGC function with the default settings. Problem is, I really don't know how it works or if the settings have been optimized for Karaoke.

I guess I need to be a bit more specific.

It looks like (at least from the advanced settings panel) that it is actually a "Dynamic Range Compressor". What I don't know is
 
1) If it's using "downward" or "upward" compression
2) What is "Enhance"?

Offline Justin

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Re: AGC
« Reply #3 on: May 27, 2014, 09:23:23 PM »
The AGC (Automatic Gain Control) basically drops the volume when it reaches the Threshold level you set. After that, it boosts the gain, attempting to keep everything level. Some hardware compressors call it "Gain Make-Up", meaning it boosts it back up to compensate for the compression.

In VDJ, I use a two-stage compression, where you of course can tweak the settings of both stages. The first stage is intended to be a slower-acting compression, just to keep the overall volume relatively even. The second stage catches the peaks (like a hard drum hit after a quiet part), and working in tandem, it generally keeps the volume even with no surprise loudness.

The "Enhance" adds back some high treble during compression. The point of this is to prevent a phenomenon called "pumping", where everything drops out every time the kick drum or bass line hits. This feature was introduced in the 1970's when Disco became popular, but it helps make the compression more transparent for most music in general.

The idea is this: You're at a gig, people are talking, other noises are happening. Your music being at a sane level and being well controlled helps to overcome this noise, and they can hear the quiet parts of a song as well since it will be brought up.

When I said it's like an FM radio station, what I actually meant was that they use heavy compression mostly to compensate for road noise, since most of their listeners are in their car. So much like road noise, the AGC feature helps overcome conversation noise at a gig. Has not much to do with the solar issues as much as just being louder (perceptually) than the next station.

Most newer music is already overly compressed as it is... but the gentle compression (with the default settings) in VDJ just helps overcome crowd noise.
-- Justin Nelson, CEO
   Next Generation Software, Inc.
   http://www.vdj.net/

Offline Hanginon

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Re: AGC
« Reply #4 on: May 28, 2014, 05:47:06 AM »
Thanks. Since I like to have the ability to get people at the bar to spill drinks in their lap, it looks like the simplest way to turn off only the second stage is to raise it's threshold from -2 db to +20 db, right?

Offline Hanginon

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Re: AGC
« Reply #5 on: June 02, 2014, 08:28:51 AM »
Wow, I guess no sense of humor here! :)

Offline Fabio

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Re: AGC
« Reply #6 on: June 02, 2014, 09:31:06 AM »
Lol...no we probably just missed the notification of your response. I've been mostly the moderator and Justin is busy working on the next version VDJ. I had to notify him privately to come and post a reply to your inquiry. I felt he needed to respond directly where I was lacking. Hopefully he answered your question.  :)
Fabio Q.
Shooting Star Karaoke

Offline Hanginon

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Re: AGC
« Reply #7 on: June 02, 2014, 06:26:38 PM »
Cool, I was afraid I might have offended someone.

I actually did cause a few spilled drinks once. I was using "another" DJ program that had a glaring fault - it's Master Volume default setting was 0 db attenuation at turn on, regardless of it's previous setting. I always do the power amps last and slowly raise their gains so there are no surprises. This one night I'm playing, power amps cranked up, rockin. For some reason I had to reboot my laptop and restart the program. I sure woke everyone up when I played that first song!

Offline vcationguy

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Re: AGC
« Reply #8 on: June 03, 2014, 10:25:48 AM »
Actually, this has been an interesting conversation.  I've learned a lot about AGC and will wear rubber pants if I'm ever at Hanginon's show so I don't get wet from spilled drinks.  lol

Offline Fabio

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Re: AGC
« Reply #9 on: June 03, 2014, 02:42:48 PM »
Quote
I actually did cause a few spilled drinks once.

Lol...yeah, you can even do that without a laptop, I've learned the hard way that when you lend your equipment to someone they're not always as careful to lower the master volume to 0 on your amp/mixer. I know I've made some people jump a few times when turning it on and volume was not lowered...the loud pop can make people jump (and sometimes duck too  ;D ).  I've come close to damaging my speakers that way.

Quote
I've learned a lot about AGC and will wear rubber pants if I'm ever at Hanginon's show so I don't get wet from spilled drinks
Make sure you wear rubber shoes too when you come to my shows...remember I take the grounding prong from my electrical plugs to prevent ground loop hum  ;)
Fabio Q.
Shooting Star Karaoke

Offline vcationguy

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Re: AGC
« Reply #10 on: June 03, 2014, 08:24:07 PM »
I thought about doing that sometimes.  I go to one place in particular that puts a buzzing sound in my speaker, I'm assuming from a bad ground.  Would it mess up my Bose L1 Compact if I did that to it?

Offline Fabio

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Re: AGC
« Reply #11 on: June 03, 2014, 09:43:03 PM »
I'd suggest doing that to a power strip not the actual Bose L1 plug, (specially if it's still under warranty).  It accomplishes the same thing.  It should be okay.  I've been doing it for years without a problem.
Fabio Q.
Shooting Star Karaoke

Offline vcationguy

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Re: AGC
« Reply #12 on: June 04, 2014, 07:24:41 AM »
I'll try that!  Thanks Fabio.

Offline Justin

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Re: AGC
« Reply #13 on: June 15, 2014, 08:35:22 AM »
I ground my equipment the Tim Allen way: break off the third prong and throw it on the ground :P
-- Justin Nelson, CEO
   Next Generation Software, Inc.
   http://www.vdj.net/

Offline Justin

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Re: AGC
« Reply #14 on: June 15, 2014, 02:38:29 PM »
If you're willing to man the slider throughout the gig, it does sound better when you turn the AGC off completely. The AGC is intended if you just want to rack up a playlist and walk away - to interact with the crowd for example. That way you don't have to jump to the mixer when a louder or softer song comes up.

However the sound quality is better with OUT the AGC feature, if you can manually keep your volume levels in check (like the old days with CDs). When I jam at home I always disable it (which I'm doing right now with Nine Inch Nails lol)... just an FYI
-- Justin Nelson, CEO
   Next Generation Software, Inc.
   http://www.vdj.net/