Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO)

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To: <d@...>, <jef@...>
Cc: linux-audio-dev@lists.linuxaudio.org <linux-audio-dev@...>
Date: Tuesday, August 21, 2012 - 8:14 pm

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On Tue=2C 2012-08-21 at 11:02 +1200=2C Jeff McClintock wrote:

=2C
=20
e
=20
=2C
Aren't there a couple of misconceptions here or at least some potentialf=
or incompatibility?
The signal itself is a digital representation of a voltage modifier. Thevol=
tage has no semantic other than its value=2C it does not represent freqor g=
ain or cutoff or anything - the semantics of what happens only occursat the=
'sink/dst' of the signal.
Consider the following points:
a. 1/Oct is not a reference value=2C it is a definition for the effects of =
amodifier signal. The value of 0.0 should definitely not refer to A440.When=
a mod signal is applied to an osc then it modifies the settingof the osc. =
You set the osc to A440 and apply 0v then it has no affect.If you apply 1v =
it should output A880=2C that is 1/octave. If you want thesignal to be able=
to reduce the frequency then you transpose the osc downby a couple of octa=
ves and then set the base mod signal at 2+ve to getback to a natural tuning=
=2C you can now reduce the frequence by 1/Octave too.
Now let's have a look at those negative values with another example:
b. It should not support negative values. Let's forget about the 1/Octfor a=
minute. This defines how a mod signal is applied: if it is appliedto an os=
c or filter coff it represents 1/Octave. It can also be applied toan amplif=
ier though. If you accept negative values you will get phaseinversion and a=
relative signal gain=2C that is probably not the intentionof the modifier =
though: if you do not restrict the signal to +ve valuesthen the source of t=
he mod signal may need to understand more aboutthe semantics of the sink - =
in the case that you have 0.0 to represent A440 then does it also have to r=
epresent 0dB (or -96dB) when itis applied to an amplifier for example. This=
is excessive since in anarbitrary system where rewiring is possible then s=
ources can be audiosignals or can be mod signals so now they need to unders=
tand where they are patched to be able to deliver a correct reference. That=
is atbest difficult and at worst unmanageable.
The above is partially opinion but is based on analogue signal pathsfrom th=
e old mono/mega synths. Agreed it might be time to move on buteither way=2C=
a modifier signal of 1/Oct is based on the 1v/Oct and inthat model the mod=
ifier signal has no reference regarding frequency=2Cgain or anything else=
=2C that reference is a function of what it is beingused to modified.
Just to be complete=2C I have no objection to such signals having someimpli=
ed semantics. There will be some apps that do not have suchrestrictions and=
this will result in inconsistencies - this is a good thing though=2C proba=
bly=2C modifier signals and arbitrary routing wasalways used as a testbed t=
o generate new sounds so bring them on.
Regards=2C nick
"I had to enter a password that needed eight characters. I used "SnowWhite =
and the Seven Dwarves"=2C' Vine=2C 2011 Edinburgh Fringe (I think).
=

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On Tue=2C 2012-08-21 at 11:02 +1200=2C Jeff McClintock wrote:
&gt=3B&gt=3B &gt=3B I think the most reasonable standard for an absolute 1/=
oct
&gt=3B&gt=3B &gt=3B frequency unit is 0.0 =3D 440Hz?
&gt=3B&gt=3B
&gt=3B&gt=3B My modular plugins use a reference of 440Hz. Also parameters a=
re ranged
&gt=3B&gt=3B between 0.0 - 10.0 but can exceed that if need be. (in a modul=
ar synth=2C
&gt=3B&gt=3B everything needs to interoperate).
&gt=3B=20
&gt=3B So for frequency 5.0 is 440Hz (Middle-A). i.e. the middle of the ran=
ge -
&gt=3B 5.0=2C is the standard 'middle' key.
=20
&gt=3B While I initially thought negative values was really weird=2C on sec=
ond
&gt=3B thought having it centred about 0.0 is nicer=2C especially consideri=
ng the
&gt=3B relative uses
=20
&gt=3B Great idea though. Octaves are far more universal than western semit=
ones=2C
&gt=3B yet trivial to convert between.
&nbsp=3B &nbsp=3BAren't there a co=
uple of misconceptions here or at least some potentialfor incomp=
atibility?The signal itself is a digital represen=
tation of a voltage modifier. Thevoltage has no semantic other t=
han its value=2C it does not represent freqor gain or cutoff or =
anything - the semantics of what happens only occursat the 'sink=
/dst' of the signal.Consider the following points=
:a. 1/Oct is not a reference value=2C it is a def=
inition for the effects of amodifier signal. The value of 0.0 sh=
ould definitely not refer to A440.When a mod signal is applied t=
o an osc then it modifies the settingof the osc. You set the osc=
to A440 and apply 0v then it has no affect.If you apply 1v it s=
hould output A880=2C that is 1/octave. If you want thesignal to =
be able to reduce the frequency then you transpose the osc downb=
y a couple of octaves and then set the base mod signal at 2+ve to get=
back to a natural tuning=2C you can now reduce the frequence by 1/Octa=
ve too.Now let's have a look at those negative va=
lues with another example:b. It should not suppor=
t negative values. Let's forget about the 1/Octfor a minute. Thi=
s defines how a mod signal is applied: if it is appliedto an osc=
or filter coff it represents 1/Octave. It can also be applied toan amplifier though. If you accept negative values you will get phaseinversion and a relative signal gain=2C that is probably not the inte=
ntionof the modifier though: if you do not restrict the signal t=
o +ve valuesthen the source of the mod signal may need to unders=
tand more aboutthe semantics of the sink - in the case that you =
have 0.0 to represent&nbsp=3BA440 then does it also have to repr=
esent 0dB (or -96dB) when itis applied to an amplifier for examp=
le. This is excessive since in anarbitrary system where rewiring=
is possible then sources can be audiosignals or can be mod sign=
als so now they need to understand where&nbsp=3Bthey&nbsp=3Bare patched to be able to deliver a correct=
reference. That is atbest difficult and at worst unmanageable.=
The above is partially opinion but is based on analogue signal paths<=
div>from the old mono/mega synths. Agreed it might be time to move on buteither way=2C a modifier signal of 1/Oct is based on the 1v/Oct an=
d inthat model the modifier signal has no reference regarding fr=
equency=2Cgain or anything else=2C that reference is a function =
of what it is beingused to modified.Ju=
st to be complete=2C I have no objection to such signals having some<=
div>implied semantics. There will be some apps that do not have such<=
div>restrictions and this will result in inconsistencies - this is a good&n=
bsp=3Bthing though=2C probably=2C modifier signals and arbitrary=
routing wasalways used as a testbed to generate new sounds so b=
ring them on.Regards=2C nick=
"I had to enter a password that needed eight characters. I used "Snow<=
/div>White and the Seven Dwarves"=2C' Vine=2C 2011 Edinburgh Fringe (I=
think).
=

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Messages in current thread:
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Jeff McClintock, (Mon Aug 20, 11:02 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 12:50 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Nick Copeland, (Tue Aug 21, 8:14 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Tue Aug 21, 9:54 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 10:29 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Tue Aug 21, 11:02 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 11:50 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Thorsten Wilms, (Wed Aug 22, 8:30 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 4:43 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Wed Aug 22, 9:12 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 9:32 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Thu Aug 23, 10:56 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Thu Aug 23, 4:06 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Thu Aug 23, 4:35 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Thu Aug 23, 5:07 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 5:37 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Nick Copeland, (Wed Aug 22, 1:24 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 1:57 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 8:59 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Nick Copeland, (Tue Aug 21, 10:11 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Jens M Andreasen, (Wed Aug 22, 3:50 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 10:52 pm)