mattcro

Has anyone made a proper VU meter effect for the kX DSP? I mean an averaging type "loudness" meter rather than the plain peak meter (as included with standard kX installation). A quick search didn't turn up anything.

A proper VU meter will show 0 VU at something like -12dB sine wave, and is used for estimating "loudness" of signals (usually found in broadcast or tape recorders). The "attack" time is usually 300ms (ie meter takes 300ms to rise to steady state) and about 1s decay time, and approximately corresponds to the ear's dynamics response.

This could be useful for music makers using kX (most of us?), eg connected to the wave output used for monitoring. That would probably mean that a "calibrate" control is needed to take account of wave level settings in the mixer panel. Options for what level corresponds to the 0 VU point would be useful.

If nobody has previously coded a VU effect, how about someone doing it as a new effect? Is it useful enough to be a part of the kX installation or effects expansion packs? I might have a go if I can get my head around the ins and outs of effect programming (more used to microcontroller stuff!).

Matt.

Russ

Be aware that kX divides the signal by 4 to allow for more headroom in the DSP, and depending on what you are using to test the VU meter, your results may be skewed because of this. I think you will find, if you connect the Wave Generator 3 plugin to an x4 plugin, and then to the VU meter, that a -12dB sine wave will show 0.

mattcro

Yeah, I'm aware that there are a bunch of places where the wave playback amplitude will be affected - mixer sliders, other plugins... What I figured was to have a "calibrate" slider/control on the VU meter effect/plugin to account for level changes, and calibrate by playing back a sine wave of appropriate amplitude in whatever editing software you use and adjusting the VU meter to read zero. You can't properly account for the effect of filter/eq so the VU meter would have to be connected as directly as possible to the wave playback source (FXbus?), not at the epilog.

Note that I'm NOT talking about the kX "Peak" or "PeakX" meters, but a real VU meter. Such a meter is featured in SoundForge (I'm trying the demo of ver 8) and I think also available in several commercial (ie expensive) VST/DX/AU/TDM etc plugins for audio mastering.

Does the kX (software drivers or DSP code) system actually divide the signal by a factor of 4, or is that headroom built into the hardware? The ADC/DAC are 18 bits which allows 12dB headroom (over 16bit), and I think the DSP unit is 32bit integer anyway, so not much problem with headroom there.

PS I'm much more familiar with electronics and audio hardware than DSP programming, so dunno if I'll get very far with coding a VU meter...

Matt.

Russ

Another thing to note is that some of the kx mixer volumes are applied inside epilog, thus the effects of those sliders will not show up on the peak meters.

As for the signals being divided by 4, here are a couple of posts from Eugene about it:
http://www.hardwareheaven.com/showpost...02&postcount=4
http://www.hardwareheaven.com/showpost...36&postcount=8

Also, I seem to remember a discussion in the forum about why they decided to do it that way (again I think it was simply for extra overhead for programming effects, etc), but unfortunately I cannot seem to locate that thread at this time.

<edit>
Actually, I think that maybe the above thread is the same thread that I was thinking of.
i.e. Another post (by Max M.) in that same thread indicates why it was done that way:

</edit>

Lex Nahumury

Ah yes analog VU meter vs Peak meter.
An old test project of mine;
http://members.home.nl/nahutec/kxplugins/vushot.PNG
(I stopped cause I couldn't find free graphics as you can see).
Iirc, a downside was the required high timer rate
for natural-looking 'needle' movement.
(a real needle can't jump instantly from let's say -24 to -6 db).
Peak Bar meters are simpler in this respect.
Oh well, anyway it works and is possible of course.

kX's 'unity gain' (0,25x) is not an issue at all.
At least; not different from if were to write a 'normal' Peak meter.
(see basic peak implementation in kX SDK)

/LeMury

radiocolonel.it

... is that the PSP Vintage Warmer Vu-meter picture?

__________________

http://www.rossanodembech.it

mattcro

That's the kind of thing I'm looking for, LeMury. It does rather look like the PSP meter (I installed VintageMeter a few days ago), which appears to use a large set of graphics to give smooth meter movement.

I figure a bar type meter (like Peak or PeakX) would do fine for a VU meter if you retain the proper meter ballistics (attack and decay rates), like the VU meters in SoundForge. I guess it wouldn't be such a big job to change the graphical output of the PSP-like kX VU meter to the standard kX Peak or PeakX style bargraph?

Thanks for the references to DSP input/output scaling etc - I'm doing some reading up, as I've never really looked "under the hood" of the kX system...

Matt.

Lex Nahumury

>>... is that the PSP Vintage Warmer Vu-meter picture?
Yes, I used it for testing purposes only ofcourse.

>>I figure a bar type meter ... would do fine for a VU meter if you retain the proper
>>meter ballistics (attack and decay rates), like the VU meters in SoundForge.
Yes, but personaly I like the 'analog' meter type better.