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