[PD] audio send recieve feedback quirk
fbar at footils.org
Fri Feb 9 11:27:58 CET 2007
padawan12 hat gesagt: // padawan12 wrote:
> I found this behaviour slightly surprising, but on reflection it makes sense.
> Pd doesn't seem to check deeply into subpatches when looking for DSP feedback
> I started making a simple waveguide synth and decided, for a change, to work on
> the feedback mechanism inside another subpatch. I kept getting DSP loop error
> even though the signal path contains a [s~] and unique matching [r~]. Making
> the feedback loop require a [send~] and [receive~] in the outermost block seems
> to defeat the use of smaller blocksizes in subpatches.
I'm away from Pd so I cannot check your patch, but your description
sounds like you're getting your execution order wrong by trying to
force a certain order through subpatches although you have a feedback-delay
You need to be aware that subpatches are evaluated in the order, the
signal cords specify.
Everything in [pd sig1~] will be calculated before everything in
sig2~. But if you have a *feedback'd* delwrite~ in sig1~, fed from a
delread~ in sig2~, then you'll get a dsp loop, because while it's okay
to have the delwrite~ before the delread~ in the DSP graph (and
actually it's wanted normally), with feedback you also have a read
(catch~ or receive~) before the write (throw~ or send~) and in
combination this is not possible in Pd as in the end it would be the
same as this loop:
[r~ a] [r~ b]
[s~ b] [s~ a]
or [a~]X[b~]. Which should come first?
Also see these two book excerpts:
Frank Barknecht _ ______footils.org_ __goto10.org__
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