#lang scribble/manual
@(require (for-label racket))

@title{subsample-offset}


Offset from synth start within one sample.

When a synth is created from a time stamped osc-bundle, it starts
calculation at the next possible block (normally 64 samples). Using
an offset-out ugen, one can delay the audio so that it matches
sample accurately.  For some synthesis methods, one needs subsample
accuracy. subsample-offset provides the information where, within
the current sample, the synth was scheduled. It can be used to
offset envelopes or resample the audio output.

See also offset-out.

Demonstrate cubic subsample interpolation.  An impulse train that
can be moved between samples.


@racketblock[
(with-sc3
 (lambda (fd)
   (send-synth
    fd 
    "s"
    (letc ((out 0) 
	   (add-offset 0))
      (let* ((i (mul (impulse ar 2000 0) 0.3))
	     (d sample-dur)
	     (x 4)
	     (o (add (sub 1 subsample-offset) 
		     (mouse-x kr 0 add-offset 0 0.1)))
	     (r (delay-c i (mul d (add 1 x)) (mul d (add o x)))))
	(offset-out out r))))))
]

Create two pulse trains one sample apart, move one relative to the
other.  When cursor is at the left, the impulses are adjacent, on
the right, they are exactly 1 sample apart.  View this with an
oscilloscope.


@racketblock[
(with-sc3
 (lambda (fd)
   (let ((t (utc))
	 (dt (/ 1 (server-sample-rate-actual fd))))
     (send fd (bundle (+ t 0.2) 
		      (list (s-new1 "s" -1 1 1 "addOffset" 3))))
     (send fd (bundle (+ t 0.2 dt) 
		      (list (s-new1 "s" -1 1 1 "addOffset" 0)))))))
]