Using Midi-Keyboard with MusE

[sadko4u]

[ Side note: If you are thinking that I could look at the LV2 units, which include pre-defined "dB" and "Hertz", to determine
how exactly to display a control, forget it. They are not reliable. LSP for example uses mysterious custom units like "G" for gain, not "dB".
So LV2 units are out of the question. ]

There are several reasons why LSP uses 'G' for gain, not 'dB':

• No one plugin format allows to define the -Inf value for dB in a right way. Since dB is logarithmic value, we always are forced to assume some values below some threshold to be -Inf decibels.
• G is just a raw multiplier to the signal. It is much easier to operate with. If you need to be compatible with generic UIs, it is a good way to allow the user to set the value '0' to gain which exactly means -inf dB level.

[merlyn]

G for gain is used in engineering. G is the name of the parameter, not a unit. Gain is defined as

Gain = V_out (Volts)/V_in (Volts)

The Volts cancel out, and gain is a number. I think "pure logarithmic units" are similarly a number and not a unit.

[Tim E. Real]

Hi @sadko4u Nice to have your thoughts on this.
Yes, that is what I do with our sliders and so on.
When they reach the first position, I force the resulting log value to jump down to 0.0
Meanwhile the second position returns my selected minimum dB converted to a log value.

As I mentioned in the post after that one, I understand about the pesky -infinite dB value.
It's tricky.
If you had chosen linear dBs for your range, you would have had to specify -80 for the minimum.
You could then maybe cut off the sound completely at this one special value of -80, but that would make things awkward.
The -80 would supposed to be a minimum and the app would dutifully show that value as the lower slider value,
not knowing that it really should have replaced it with -infinity.

Tricky.

Still, VST and some LADSPA plugins somehow manage all of this in linear ranges without even having a 'logarithmic' property.
Possibly because the range is just linear 0.0 to 1.0, and at 0.0 they cut the sound off completely ?

(Sorry, I didn't mean to pick on the awesome LSP suite, it was just one random example of the challenges faced.)

[Tim E. Real]

Still, VST and some LADSPA plugins somehow manage all of this in linear ranges without even having a 'logarithmic' property.
Possibly because the range is just linear 0.0 to 1.0, and at 0.0 they cut the sound off completely ?

So, with a range of 0.0 to 1.0, how does a VST host know what text to display for lower and upper ranges and the value, for dB controls?

Ah yes, well, VST has a trick up its sleeve.
You don't compose this text yourself !
VST tells you what text to display, by using a function that gives you a text string containing all the necessary text.

Great, except... It's a really awkward system.
The text cannot even be separated into various components that we could put into our sliders' spin box 'buddies', or other places.

QTractor uses that VST text string.
Open a VST generic UI in QTractor and you can see how awkward this is.
You are forced to adjust a slider or spin box while looking at this piece of text in a separate label.
I can only imagine QTractor's author must have been as befuddled as I would be.
And yes, I am considering using that text in MusE. (There really is no choice, the given text must be used.)

Tricky tricky tricky...