[Csnd] RMS feedback system help
| Date | 2014-08-06 11:55 |
| From | Askwazzup |
| Subject | [Csnd] RMS feedback system help |
Hello friends!
For the past few months i concentrated on learning a bit of supercollider,
and now that i'm back to learning csound again, i feel i'm a bit rusty.
This is an example from the floss manual, it is supposed to lower the amount
of feedback when it gets too high, but there are a few places where i'm not
sure what's going on:
------------------------------------------------------------------------------------------------------------------------------------------------------
giSine ftgen 0, 0, 2^10, 10, 1 ;table with a sine wave
instr 1
a3 init 0
kamp linseg 0, 1.5, 0.2, 1.5, 0 ;envelope for initial input
asnd poscil kamp, 440, giSine ;initial input
if p4 == 1 then ;choose between two sines ...
adel1 poscil 0.0523, 0.023, giSine
adel2 poscil 0.073, 0.023, giSine,.5
else ;or a random movement for the delay lines
adel1 randi 0.05, 0.1, 2
adel2 randi 0.08, 0.2, 2
endif
a0 delayr 1 ;delay line of 1 second
a1 deltapi adel1 + 0.1 ;first reading
a2 deltapi adel2 + 0.1 ;second reading
*krms rms a3 ;rms measurement
printk 1,
delayw asnd + exp(-krms) * a3 ;feedback depending on rms++
a3 reson -(a1+a2), 3000, 7000, 2 ;calculate a3*
aout linen a1/3, 1, p3, 1 ;apply fade in and fade out
outs aout, aout
endin
----------------------------------------------------------------------------------------------------------------------------------------------------
On this line:
*delayw asnd + exp(-krms) * a3 *
1) a3 is being used, but at the start of the instrument it's initialized to
0, is that how it's supposed to work? First time the delayw is modified by
+0, and then whatever comes out of the reson filter?
2) Also, i'm not really sure how does delayw work? In the manual it says it
writes to a digital delay line. What is a digital delay line?
On this line:
*a3 reson -(a1+a2), 3000, 7000, 2*
3) Why is (a1+a2) with a minus sign?
--
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|
| Date | 2014-08-06 17:40 |
| From | Andres Cabrera |
| Subject | Re: [Csnd] RMS feedback system help |
Hi,
On Wed, Aug 6, 2014 at 5:55 AM, Askwazzup <aistiskaikaris@mail.com> wrote: 1) a3 is being used, but at the start of the instrument it's initialized to init works only at init time, i.e. when the note starts, so only the first control pass will have 0s for a3, the next pass it will have the previous value of a3 (because it hasn't been rewritten by the reson line (so this in fact delays a3 by one control block, which is a bit unusual as the behavior changes if you change ksmps, not sure if this is deliberate) 2) Also, i'm not really sure how does delayw work? In the manual it says it It's a delay line made of digital samples. Digital delay lines work like analog ones, where you have a "read" head and a "write" head, that's why you have two opcodes. You can hide this inside a single opcode like vdelay3.
It looks like the purpose is to invert the phase so that it cancels the input signal in: delayw asnd + exp(-krms) * a3 But with filtering and the ksmps delay, you can't really predict that it will cancel... Cheers, Andrés
|
| Date | 2014-08-06 19:12 |
| From | Askwazzup |
| Subject | [Csnd] Re: RMS feedback system help |
Thank you Andres! -- View this message in context: http://csound.1045644.n5.nabble.com/RMS-feedback-system-help-tp5736633p5736656.html Sent from the Csound - General mailing list archive at Nabble.com. |