On the subject of the metering display behaving erratically (as distinct from displaying incorrect values) ... standard zyn refreshes the gui at 25 fps, and to my mind that leaves the metering looking unduly sluggish.

I've noticed consistent comment along the way (LAU/LAD?) that there's no point refreshing such display elements faster than 60 or so times per second. Yoshi currently uses 50, which I quite like, but if others hate it I'm interested to hear.

On Thu, Oct 22, 2009 at 10:21:50AM +1100, cal wrote: That just depends on the algorithm driving the meter. Jkmeter refreshes at 25 Hz by default, and the peak indication doesn't look sluggish at all (the RMS one does, but that is by design). If your meter is supposed to display peak values then the algorithm than computes them should hold the max value for some time before letting it fall back, in jkmeters this is half a second. If you do that the refresh rate just determines how smooth the fallback is, and nothing else.

On Sat, Oct 24, 2009 at 05:51:19PM +1300, Chris Edwards wrote: It just determines how smoothly the display will appear. The dynamic behaviour of jkmeters (and also of the VU and PPM meters in jmeters) is very strictly defined. The values that are displayed are calculated in a way that does not depend on the display update rate, and (within reasonable limits) also not on the Jack period size. A level meter would just be useless eye-candy otherwise. There is indeed a 'window' for the RMS value, but don't imagine it as being rectangular, i.e. with all samples having the same weight. The window is more like an impulse with a slightly smoothed front (which determines how it will react to short bursts) and an exponential decay. It is the impulse response of a critically damped 2nd order filter acting on the square of the signal. The controlled fallback of the RMS indication is not artificial (as it is for the peak value), it *is* the shape of the window. Even in that case you would need a defined fallback rate. Lower peak levels should be shown only if they are not immediately following a much higher peak, otherwise the peak level will jump up and down all the time. In other words the bump-up should happen only if the current input is higher than the fallback of the previous peak. Having a visible fallback is easier on the eyes. Ciao,

On Sat, Oct 24, 2009 at 12:16:58PM +0100, Folderol wrote: Well, it's not really complicated... 'Traditional' VU meters had no active electronics at all, just a bridge rectifier and a resistor. The dynamic response was determined only by the mechanics of the meter. This means that a 'real' mechanical VU was not just a V or A meter with a different scale, it had to be engineered to have the right response. Now such a moving coil meter is just a classic mass + spring + damping system, which corresponds to a second order low pass filter. So to get the correct response from a software VU you take the absolute value of the signal and apply the low pass filter. For a VU the filter was defined in the time domain: with a step input It should reach 99% of the final value in 300ms, overshoot to between 101% and 101.5%, and finally come to rest at 100%. The overshoot means sub-critical damping, so the filter is 'ringing' (but not much). The -3dB frequency for a VU filter is around 2Hz. The filter used in jkmeter is similar, but has exactly critical damping, it does not overshoot, and the -3dB frequency is around 1Hz. The other difference is that the input to the filter is not the absolute value of the signal but the square of it. This means you can't direclty compare the 'speed'. For short signals (less than 125 ms) the K meter is faster than a VU would be, for longer ones it is a bit slower, and it also falls back slower than a VU. If anyone is interested in the exact time and frequency domain curves just ask off- list.

On Sun, Oct 25, 2009 at 07:32:37AM +1100, cal wrote: :-) That probably means you are US based, as I've *never* seen a real VU in any European public broadcast studio (the 'pirates' had them but reverted to peak meters when they becamce legal and could afford UK gear). I got my exposure to VUs by occasionally working on US manufactured desks (MCI!) and aligning Ampex multitracks...

The dynamic behaviour of jkmeters (and also of the VU and PPM meters in jmeters) is very strictly defined. The values that are displayed are calculated in a way that does not depend on the display update rate, and (within reasonable limits) also not on the Jack period size. A level meter would just be useless eye-candy otherwise. [...]