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10-20-2021, 01:01 PM
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#1
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Human being with feelings
Join Date: Feb 2012
Location: Sweden
Posts: 1,206
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Reacomp's threshold is 3dB off?
I'm in a phase where I'm measuring up my main plugins tools and stuff. Right now mostly dynamic tools, compressors and stuff.
I got 3-4 different methods going to measure them all up, so I can also cross-reference results if any of them shows ambigous results.
Turns out, when I set Reacomp's threshold to -20, the threshold actually resides at -17dBFS. I'm using attack 1ms, release manual 50ms, ratio 4:1, knee off, RMS size 1ms, and no filters or precomp enabled. '
At first I thought there must be something wrong, but I crossreferenced all methods and they all show the same thing. They all also indicated no soft knee at all was measurable. Rock hard knee. Unusually rock hard actually.
Then I looked at the gain reduction meter in Reacomps GUI, set the threshold to -20 again, and sent a -17dBFS 1kHz sine tone through Reacomp, and even Reacomp's own GR meter confirms that it starts compressing first at -17dBFS, no matter how steep you set the ratio. Doesn't start at -20. With a static sine tone at -17dBFS, the GR meter compresses 0,1dB.
Also it doesn't have anything to do with sending a stereo tone (both channels) or a mono tone through it. It shows the same either way. (a stereo tone would be 3dB higher to the compressor if it is using a mono sum process to read the level, which I don't think it does).
Now I'm not this nitpicky just to be a nerdy nitpicker. I find Reacomp a great and useful tool and I will continue to think so and still use it alot. But I can't help but being a little curious as to why this is. I wouldn't be so bold as to yell "Bug" quite yet though.
If anyone would care to confirm this is the case for you too, please let us know. Or if this is not true for you (in which case I probably won't believe you :P). I'm on Win, Reaper 6.38.
And further, why does this happen? Like I said, I don't mind if it does, because I'll just set the threshold to compensate. But something in me says this wasn't the intention of the makers.
Thanks for any input
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There are only two kinds of people in the world: those who entertain, and those who are absurd.
- Britney Spears
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10-20-2021, 01:13 PM
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#2
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Human being with feelings
Join Date: Dec 2012
Posts: 7,295
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RMS is not peak. A 1K tone has exactly 1ms period, so we’d expect it to integrate to half the square of two times the peak, which works to pretty close to -3db.
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10-20-2021, 01:16 PM
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#3
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Human being with feelings
Join Date: Sep 2008
Location: Sweden
Posts: 7,432
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I don't know how you are testing, but I did the following:
Track 1, sine wave 1 kHz at -18 dB peak, no master se
Track 2, receives from Track 1, polarity inverted
Track 3, receives from Track 1, has ReaComp with pre-comp = attack = 0, release 100 ms, ratio 2, knee 0, lo-hi 0-20kHz, RMS size 0.0 ms
This nulls perfectly when threshold is at -18.0 (and above). It does not null fully when threshold is at -18.1 (or below).
So I would say that there is something with your testing. Probably that you have attack and RMS size not set to zero.
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// MVHMF
I never always did the right thing, but all I did wasn't wrong...
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10-20-2021, 01:20 PM
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#4
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Human being with feelings
Join Date: Feb 2012
Location: Sweden
Posts: 1,206
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Quote:
Originally Posted by ashcat_lt
RMS is not peak. A 1K tone has exactly 1ms period, so we’d expect it to integrate to half the square of two times the peak, which works to pretty close to -3db.
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Ah. So we are to understand Reacomp's threshold setting refers to RMS?
I could buy that. But I'd have to include that most compressors I've tried out - using the test methods above (not just looking at the GUI metering) - uses peak as their threshold level. Most start reducing volume at very close to the set threshold value.
In light of that, makes me uncertain still what to think ..
__________________
There are only two kinds of people in the world: those who entertain, and those who are absurd.
- Britney Spears
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10-20-2021, 01:28 PM
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#5
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Human being with feelings
Join Date: Sep 2008
Location: Sweden
Posts: 7,432
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Quote:
Originally Posted by Colox
Ah. So we are to understand Reacomp's threshold setting refers to RMS?
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No it doesn't, see my null test. But the RMS size setting affects the compressor's behavior, which is why the threshold is only exact when RMS size is 0 (again, see my null test described above).
__________________
// MVHMF
I never always did the right thing, but all I did wasn't wrong...
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10-20-2021, 02:06 PM
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#6
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Human being with feelings
Join Date: Feb 2012
Location: Sweden
Posts: 1,206
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Quote:
Originally Posted by Fabian
I don't know how you are testing...
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Yeah, should've meantioned my methods in detail but didn't want to make 1st post wall of text. My testing involves tools like DDMF Plugindoctor, Compressor Measurement Toolbox, and different combinations of rendering and cancelling original signal out. Not your way (below) though.
Quote:
Originally Posted by Fabian
.. but I did the following:
Track 1, sine wave 1 kHz at -18 dB peak, no master se
Track 2, receives from Track 1, polarity inverted
Track 3, receives from Track 1, has ReaComp with pre-comp = attack = 0, release 100 ms, ratio 2, knee 0, lo-hi 0-20kHz, RMS size 0.0 ms
This nulls perfectly when threshold is at -18.0 (and above). It does not null fully when threshold is at -18.1 (or below).
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I confirm that.
I tested it with RMS=1ms. Any lower tends to cause too much distortion on lowend material for my liking.
Quote:
Originally Posted by Fabian
So I would say that there is something with your testing. Probably that you have attack and RMS size not set to zero.
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Yes, I seldom use an attack time lower than 2ms, and 1 for RMS. I was testing it close to how I use it normally. Lower attack than 1 usually cuts into the original waveform so eagerly that it muddies up. That's also true for many compressors.
Writing this response, making screenshots, I noted that the attack time does have a significant impact on the level of the threshold in Reacomp. Setting the attacktime to higher than 0, raises the threshold level. This is not too common for compressors (tried alot lately). Many of them maintain the threshold level still. But it does still make sense theoretically.
Here's a screenshot of Plugindoctor with Reacomp set to 0ms attack time and threshold = -20. It's slightly higher than -20.
And here the same settings but attack time 2ms.
Above (2ms attack and RMS 1ms) the threshold both raises up and also "softknees". It makes sense to think "it takes some extra time for the compressor to fully enable the volume reduction", but the fact is most other compressors don't do that. Tried so many the last week. They commonly softknees when softknee is enabled. Don't have enough measurements or thought enough as to argue why this is. But there's much of where my thoughts about this came from. Seems the attack/RMS influences the threshold level of Reacomp.
Also, a screenshot from CMT, confirming the threshold averages on -17 when the setting on Reacomp is on -20 (using attack time 2ms):
I'm not making a querulant argument about it, I just felt like showing I didn't come to this impression lightly, however misinterpreted it might be
If you don't mind, would you set threshold to -20, attack to about 2, RMS to 1, and put a -17dBFS tone through it, and look at the GR meter while you very the tone volume input? It should show indicate compression starting at ~17. Just to see what I saw.
This helped me get a better picture of what's going on with Reacomp
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- Britney Spears
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