So whenever analogue equipment needs to work with digital equipment it is configured so that 0dB in the analogue domain is at some (hopefully calibrated and consistent) level below 0dB in the digital domain. The actual value is

Just a note: I personally don't like VUs in the digital domain.

I prefer Bob Katz' K metering system (K12, K14, K20) with well defined headrooms. Check out this page for a detailed description on the K metering system: http://www.digido.com/level-practices-part-2-includes-the-k-system.html Note that many commercial software vendors ship analyzer plugins using the K system, i.e. RME's DigiCheck. I'd suggest to go for this, too.

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Fons Fons Adriaensen wrote: You are not changing the signal, you are changing the amount of headroom the VU meter has. http://www.reference.com/browse/wiki/Headroom To put it simply, 0dB on analogue equipment is indicating the optimal level. There is an amount of headroom above that level before distortion will occur. In the digital domain 0dB is the absolute maximum level and distortion occurs at this point.. So whenever analogue equipment needs to work with digital equipment it is configured so that 0dB in the analogue domain is at some (hopefully calibrated and consistent) level below 0dB in the digital domain. The actual value is arbitrary and depends part on preference and part on the quality of your analogue gear. So if you elect to have 9dB of headroom on you analogue gear, then you'd select -9dB on the plugin, and then VU metering 0dB will have the peak metering -9dB. - -18 to -9 is common, but I've seen all sorts of things. I can't reproduce that. A clue may help. (distro, arch, kernel, soundcard, host etc). The plugins have been built on ubuntu studio (hardy) x64 and tested on ubuntu jaunty (x64), Arch linux (x64) & AV linux (x32). Correct since this plugin isn't in the analogue domain. It's a simulant. It does convey the 'perceived volume' of a signal better than a peak meter and does help if you are mixing to tape. please advise where this standard is. AFAIK there are just algorithms that simulate the behaviour of electronic RC circuits with varying degrees of success, and yes I have a munge. Sorry if it disturbs you. Apart from the relative phase difference between the left and right channels. With the demise of vinyl the importance of phase has been lost too to some extent so it doesn't surprise me you don't what this meter is for or what it's trying to tell you. On vinyl out of phase signals make the needle go up and down instead of side to side, this makes the needle bounce out of the groove. Worse still is what happens when you have low frequency out of phase sounds. The wave length (on the vinyl) is large enough for the cutter to go through the vinyl... => This is why everything below 200Hz is mono'd for vinyl during mastering in case you were wondering. A quick guide to interpreting the phase meter: * A mix that never goes +/- 20 is too mono. Pan something. Create some space with reverb. etc * A mix that spends all it's time between +/- 45 is as 'wide' as you want to get. You should able to see some variety in there of course, ie a verse and a chorus should be different widths. * If the phase meter spends any time over +/- 55 then audible cancellation will occur if the mix is mono'd or listened to from a distance. * Any travel over +/- 60 is trouble, there is something out of phase in the mix. although this may sound great with your head between the speakers it's going to suck when heard anywhere else. * If the meters stays at +/- 90 then the whole mix is out of phase :) regards, Fraser _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev(a)lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev

On Sun, 2009-08-23 at 18:26 +0200, Ralf Mardorf wrote: Of course they read different things! They are measuring different things! The VU is a slow response meter (300ms integration time IIRC)intended to (badly) track perceived volume, the meters on (most) DAWs are closer to digital peak meters intended to monitor absolute peak levels. Both are useful and both have a place. The differences each time you play are why we leave the thick end of 20db of headroom between 0 VU and 0dbFS, you should (in a production environment) never be going anywhere near 0dbFS (there is no need for it in the age of 20+ bit ADC noise floors). Why is it dangerous? it tells you something about RMS levels which you would not otherwise know (peak reading meters provide little guidance as to perceived volume). Now, I don't know about this particular implementation (I don't have an LV2 host to hand), but a good implementation of a VU would not be an inherently bad thing to have available. Regards, Dan.

The key is that every stage has to have a known calibration, which is actually fairly common with professional cards.

Lets say your card is aligned so that 0dbFS = +18dbu (EBU standard), then 0Vu = +4dbu = - 14dbFS, so a software VU calibrated for 0Vu = -14dbFs should read the same as an external Vu calibrated for +4dbu = 0Vu. If it does not then either a calibration setting is off somewhere or one of the meters is faulty.

actually fairly common with professional cards.

VU meter: Maybe you should call it 'analogVUemu'.