rsc3/doc/help/ugen/io/in-feedback.help.scm

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2022-08-24 13:53:18 +00:00
;; (in-feedback num-channels bus)
;; Read signal from a bus without erasing it, audio rate.
;; The output (out) ugens overwrite data on the bus, giving this bus a
;; new timestamp so that any input (in) ugen can check if the data was
;; written within the current cycle. The next cycle this data is still
;; there, but in case of audio one normally doesn't want an in ugen to
;; read it again, as it might cause feedback.
;; This is the reason why in ar checks the timestamp and ignores
;; everything that was not written within this cycle. This means that
;; nodes can only read data from a bus that was written by a
;; preceeding node when using the in ar ugen which overwrites the old
;; data. This is good for audio, but for control data it is more
;; convenient to be able to read a bus from any place in the node
;; order.
;; This is why in kr behaves differently and reads also data with a
;; timestamp that is one cycle old. Now in some cases we want to be
;; able to read audio from a bus independant of the current node
;; order, which is the use of inFeedback. The delay introduced by
;; this is at a maximum one block size, which equals about 0.0014 sec
;; at the default block size and sample rate.
;; Audio feedback modulation.
(let ((f (mul-add (in-feedback 1 0) 1300 300)))
(audition (out 0 (mul (sin-osc ar f 0) 0.4))))
;; Evaluate these in either order and hear both tones.
(let ((b (add num-input-buses num-output-buses)))
(audition (out 0 (in-feedback 1 b))))
(let ((b (add num-input-buses num-output-buses)))
(audition (mrg2 (out b (mul (sin-osc ar 440 0) 0.1))
(out 0 (mul (sin-osc ar 660 0) 0.1)))))
;; Doubters consult this.
(let ((b (add num-input-buses num-output-buses)))
(audition (out 0 (in 1 ar b))))
;; Resonator, see localout for variant.
(let* ((b (add num-input-buses num-output-buses))
(p (in-feedback 1 b))
(i (impulse ar 1 0))
(d (delay-c (add i (mul p 0.995))
1
(sub (recip 440) (recip control-rate)))))
(audition (mrg2 (offset-out b d) (offset-out 0 p))))
;; Compare with oscillator.
(audition (out 1 (mul (sin-osc ar 440 0) 0.2)))