I would like to create a sound signal one sample value at a time by means of a loop. The process should run like this:
- Ask for the start values of x_old and v_old.
- Calculate x_new and v_new from x_old and v_old by means of certain recursive relations.
- Export x_new as the current audio sample value.
- Rename x_new and v_new to x_old and v_old .
- Goto 2.
The loop should take exactly one sample time long, so that one sample value is produced during one sample time.
Is there a way to do this in Csound?
Looks like this kind of implicit loop will do the trick?:
<CsoundSynthesizer>
<CsOptions>
-odac
</CsOptions>
<CsInstruments>
sr = 44100
ksmps = 1
nchnls = 2
0dbfs = 1
instr 1
kf = 440
kres timeinsts
aOut = sin(2*$M_PI*kf*kres)
outs aOut, aOut
endin
</CsInstruments>
<CsScore>
i 1 0 6
</CsScore>
</CsoundSynthesizer>
yes, ksmps = 1 is the key 
<CsoundSynthesizer>
<CsOptions>
-o dac
</CsOptions>
<CsInstruments>
sr = 44100
ksmps = 1
nchnls = 2
0dbfs = 1
instr 1
;steps of 1 sample time
kdelta_t = 1/sr
;input R/m
ka = 7643021
;measuring time passed
kres timeinsts
if kres < 0.0001 then
kx_old = 1.0
kv_old = 0
else
kx_new = kx_old + kv_old*kdelta_t
kv_new = kv_old + -1*ka*kx_old*kdelta_t
kx_old = kx_new
kv_old = kv_new
endif
;correction of amplitude drift
kx_old limit kx_old, -1, 1
aOut = kx_old
outs aOut, aOut
endin
</CsInstruments>
<CsScore>
i 1 0 5
</CsScore>
</CsoundSynthesizer>
The above was what I planned to do, and it’s working now by giving a harmonic signal except for one thing: the amplitude keeps on rising if not checked by limiting the signal (as I have done here by means of the limit opcode). Why doesn’t the amplitude stay at the starting value?
From a quick glance it seems that you have feedback with multiplication. This line is causing the blowup:
kv_new = kv_old + -1*ka*kx_old*kdelta_t
add and printk under it and see how it grows…
kv_new = kv_old + -1*ka*kx_old*kdelta_t
printk .2, kv_new
I’m trying to do something similar as this: https://evgenii.com/blog/programming-harmonic-oscillator/ (see 3. and further)
But I don’t have the moving picture and I’m using Csound. There is also feedback on the web application but no blowup there…
Looks interesting. I don’t have time to delve into it right now, but I’m sure it’s just a simple mistake in your code. That line is clearly a problem.
Problem solved with sr = 300000000 and “Render to file” which gives a wav file with a nice constant harmonic signal with hardly any distortion (no limiting needed any more):
Begin of signal:
End of signal:
