Meter scale

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Michiel Bouwmeester
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Joined: 04 Nov 2012 16:07

Meter scale

Post by Michiel Bouwmeester » 24 Aug 2014 10:19

Hi Bernd,

Would it be possible to make the meter scale switchable between the current scale and a 0dBFS max scale?

Grtx Michiel

Michiel Bouwmeester
Posts: 69
Joined: 04 Nov 2012 16:07

Re: Meter scale

Post by Michiel Bouwmeester » 24 Aug 2014 12:28

May be plans after today ? :D

I ask because it would make sense to have a 0dBFS scale, specially on the "master" out channel.

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radio42
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Re: Meter scale

Post by radio42 » 24 Aug 2014 21:47

No plans yet. But theoretical possible :-)

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Re: Meter scale

Post by radio42 » 28 Aug 2014 20:05

I looked at it a bit closer...
Actually the current scale is a logarithmic dB FS scale!

The only difference is that I display possible values above 0 dBFS. And this because internally I process everything in 32bit floating precision. Which allows values above 0 dB.

So a real dB FS would consider a max. output resolution and would be limited to max. value at 0 dB FS.
This would have the disadvantage that you do not see how much the output would be clipped.

So I am not sure if that is really what you want.

As for the rest (all values below 0) the current scale is identical to a dB FS scale.

Michiel Bouwmeester
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Re: Meter scale

Post by Michiel Bouwmeester » 21 Sep 2014 18:36

Ok, i understand this. It would mean (if i understand correct) only the text needs to change. The extra headroom should not be used... as 0dbfs is the maximum. (It would also make the meters look and feel the same as all the other digital meters out there)

The "over 0dfs".. that is the whole problem. In some scenarios (after DA conversion) it is all ready possible (but not wanted) to get levels above 0dbfs.. If you look at the free meter from Orban they try to show this in the reconstructed peak level.(this is the value they calculate after the DA step is made.)

If i am correct currently it is common practice/advised to setup a level of -6dbfs as max peak level (protection limiter set to this level to guard it) This does leave 6db headroom for unintended peaks in the audio that might slip through. (of course PF has no problem here, as you said due to the 32bit processing but the singal should go out to the stream of DA on a propper level)) Only problem here could be how to calibrate this (as an example) to a stream or audio output. May be a calibrate test tone or file could help here.

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radio42
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Re: Meter scale

Post by radio42 » 21 Sep 2014 19:55

Not sure what you mean by "text should not be used"?! But for the rest yes.
The "over 0dfs".. that is the whole problem...
That's exactly why I do display the over 0dB values! Otherwise you are NOT able to level the output correctly. As everything over 0dB MIGHT be clipped in the final soundcards output!
Any level at the DA stage (soundcard output) can ONLY be calculated by the soundcard.

No, I guess the "common practice of a -6dB FS" setup is simply because many people come from the analog world, where a certain "headroom" does exist.
So if you level everything to -6 dB in average you are kind of creating a headroom in the digital world.
Note, that there can not really be any 'unintended peaks in the audio'. Any DA input can also never generate a signal above 0dB. It is purely the subsequent sound processing (e.g. FX, DSPs, VSTs etc.) which might generate those peaks!

However, that has nothing to do with the shown meter scale!
Again, any level above 0dB is a candidate for clipping in the output. If I wouldn't show the levels above 0dB...you wouldn't know how much to lower the output level! That's why I do display it.
Not displaying it on a meter scale wouldn't prevent any clipping at all!

Yes, you can use a test tone to calibrate things...again...the meter scale would change things at all here.

Michiel Bouwmeester
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Re: Meter scale

Post by Michiel Bouwmeester » 21 Sep 2014 21:29

Hi Bernd,

I do understand why you display above 0db.. but it still should not be there :) 0dbfs should be the maximum and people should adjust there level to not peak at 0dbfs. That is why the -6dbfs calibration is used, exactly as you say to create headroom. The protection limiter is there to hardlimit in case the audio is louder, live show or whatever reason, specially because the software can go over the 0dfbs mark.

Any DA input can also never generate a signal above 0dB That is correct, but as you say correct the processing can easalliy push singals above due to its 32 bit architecture. By sending signals to the DA above 0dbfs the DA becomes a brickwall limiter/clipper, and this is exactly one off the problems/risks. Also a signal above 0dbfs send to an mp3 stream will get clipped by the stream encoder.. it cannot go beyond.

Would it not be better to have metering at 0dbfs max scale, with a "over" indication? That would make the metering look and feel as the industry metering and still give an indication when signals are over 0dbfs. (most do have an "over' indication) By taking away the part above 0dbfs people will aim for that, now a lot of people (specially those used to analogue) will try to max out the signal and thus (possibly) overloading the DA.

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Re: Meter scale

Post by radio42 » 21 Sep 2014 22:16

I am sorry, but I disagree.
A 0 dB FS display simply CUTS-OFF any values above it's theoretical max. value of 1.0 (when used with 32-bit float processing)!

A real 0 dB FS display only makes sense with devices having a real max. value, e.g. DA's using a 16-bit or 24-bit integer processing bit depth.

Some other questions:
a) Would you calibrate your sound just because your meter display is a 0 dB FS display?
No, you calibrate it because you want headroom.
So the meter display makes no difference. You can still use the current meter display to perfectly detect values peaking at 0 dB FS as well as you can still perfectly calibrate your audio at 0 dB FS.
The used meter display does make no difference! All values at 0 dB and below 0 dB exactly match a 0 dB FS meter display!

b) How would you differentiate a valid and non-clipped 0 dB FS value (max) from a clipped valued above 0 dB?
With a simple 0 dB FS meter you can not...that's why I don't use it.

c) Why just an 'over' indication when you can exactly display the dB value above?
I do not an advantage here, just a disadvantage. When its at +3 dB, I know, that I should at leave lover the volume (gain) by - 3 dB.
With just an over indicator its try and error.

Again: the existing meter is as exact as any other 0 dB FS meter display...it simply doesn't cut things off, but is able to display things above 0 dB - that's all.

No, they would NOT overload it more with the current level meter!
The current level meter displays ANY value at or above 0 dB FS in RED.
So if you see something RED in the current level meter, you know that....

I am really sorry, but I do not see a single advantage in your arguments to cut off (and not display) any levels above 0 dB.

Michiel Bouwmeester
Posts: 69
Joined: 04 Nov 2012 16:07

Re: Meter scale

Post by Michiel Bouwmeester » 22 Sep 2014 07:00

Hi Bernd,

I fully agree with our disagreement :) For the argument I will response, altough I understand we are "stuck" here ;)

radio42 wrote:I am sorry, but I disagree.
A 0 dB FS display simply CUTS-OFF any values above it's theoretical max. value of 1.0 (when used with 32-bit float processing)!
There should not be any signal above! Check any of the professionally used software (Nuendo, Pro tools and such) None have metering above 0dbfs.

A real 0 dB FS display only makes sense with devices having a real max. value, e.g. DA's using a 16-bit or 24-bit integer processing bit depth.

it is because of this lack of reference I would like to see meters calibrated to 0dbfs. Your meters display correct but they show something that should never be there.
A simple "over" is more then enough, in a good setup it simply should never be lit!



Some other questions:
a) Would you calibrate your sound just because your meter display is a 0 dB FS display?
No, you calibrate it because you want headroom. No you calibrate the meters and then adjust the audio processing to the propper level.
So the meter display makes no difference. You can still use the current meter display to perfectly detect values peaking at 0 dB FS as well as you can still perfectly calibrate your audio at 0 dB FS. The current meters can perfectly be used, but there is a part that should not be there. And people will try to push levels above the odb mark on the current meters... because they dont know, care or understand how they should level out. By having a visual 0dbfs max scale the instanly know it is the max. Now they believe +3 db is max.. wich it is not.. that is 3db to much. A simple "over' indication is clear for everybody: The signal is to high.

The used meter display does make no difference! All values at 0 dB and below 0 dB exactly match a 0 dB FS meter display! See the point above

b) How would you differentiate a valid and non-clipped 0 dB FS value (max) from a clipped valued above 0 dB?
With a simple 0 dB FS meter you can not...that's why I don't use it. Again, there should be no signal above 0dbfs. An over indication does the trick.

c) Why just an 'over' indication when you can exactly display the dB value above?
I do not an advantage here, just a disadvantage. When its at +3 dB, I know, that I should at leave lover the volume (gain) by - 3 dB.
With just an over indicator its try and error. For the advanced user this might be true, for 95% of the others it is not. They will all think they that they van send signal up to +3db. I have had a lot of conversations lately about meters and levels and I am shocked by the amount of people sending out at way more then 0dbfs. This is partly because they see a meter go beyond 0...

Again: the existing meter is as exact as any other 0 dB FS meter display...it simply doesn't cut things off, but is able to display things above 0 dB - that's all.

No, they would NOT overload it more with the current level meter!
The current level meter displays ANY value at or above 0 dB FS in RED.
So if you see something RED in the current level meter, you know that.... For a lot of people red is cool apparently :lol:

I am really sorry, but I do not see a single advantage in your arguments to cut off (and not display) any levels above 0 dB.

Michiel Bouwmeester
Posts: 69
Joined: 04 Nov 2012 16:07

Re: Meter scale

Post by Michiel Bouwmeester » 22 Sep 2014 14:56

radio42 wrote:
...and people will try to push levels above the 0 dB mark on the current meters
Why should that be? Do you assume any user is dump? I guess almost every user will understand, that ANY LEVEL ABOVE 0 dB MIGHT LEAD TO DISTORTION. It is that simple... people who do NOT understand this should not work for a radio station ! ;-) I agree on that... but as you know it happens a lot, specially in this time of web stations everywhere


Why?
Pretty simple: In the analog world most meter have been designed, so that the overload indicator should only lit for a few times to be perfectly leveled... That is a wrong idea.. even in the analogue world the "peaks" should be respected, but you are right... most will set it up to show an over know and then. so they do the same with a 0 dB FS meter...they increase the level, so that overload indicator only lits sometimes, but not constant. Problem is that for the not so experienced people 0db does not show as a maximum now.. +3db is the maximum, even tho it colors red on the last 3db. BUT in the digital world, this is total wrong! It should NEVER lit at all! You are right, but most digital over meters do trigger slightly before odbfs. (With most you can set where they trigger, -0,2 or -0,4dbfs)


You can only solve your problem by teaching people - that's all. This is a good point :-)
For the advanced user this might be true, for 95% of the others it is not
Now you are inconsistent with yourself!
Above you say: " in a good setup it simply should never be lit"...but a good setup requires an advanced users! That is why we have this discussion, trying to get stuff as simple as possible to have "lesser" advanced users be able to make a good setup, right? If not we can stop now. I KNOW how to setup a meter/audio chain and I dare to say that our stream is very good regarded to level and compression. It is not for me :) I am simply trying to make things beter/easier.


And as you do this 'MIC level calibration' EVERY TIME someone sits down in front of a MIC - my personal opinion is, that a level meter going above 0 dB helps.
But...as said, it is a personal taste... I fully agree that people should calibrate the mics every time they go in front of one. No argument here from me I just feel different about the "meter" matter, lets keep it at that :)

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