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

@title{(pv-hainsworth-foote buffer proph propf threshold waittime)}


fft onset detector based on work described in

  Hainsworth, S. (2003) Techniques for the Automated Analysis of
  Musical Audio. PhD, University of Cambridge engineering dept. See
  especially p128. The Hainsworth metric is a modification of the
  Kullback Liebler distance.

The onset detector has general ability to spot spectral change, so
may have some ability to track chord changes aside from obvious
transient jolts, but there's no guarantee it won't be confused by
frequency modulation artifacts.

Hainsworth metric on it's own gives good results but Foote might be
useful in some situations: experimental.

buffer - fft buffer to read from

proph - What strength of detection signal from Hainsworth metric to use.

propf - What strength of detection signal from Foote metric to
        use. The Foote metric is normalised to [0.0,1.0]

threshold - Threshold hold level for allowing a detection

waittime - If triggered, minimum wait until a further frame can
           cause another spot (useful to stop multiple detects on
           heavy signals)

Default values in sclang are: proph=0.0, propf=0.0, threshold=1.0,
waittime=0.04.

--

Just Hainsworth metric with low threshold


@racketblock[
(with-sc3
 (lambda (fd)
   (async fd (b-alloc 0 2048 1))))
]


@racketblock[
(let* ((source (sound-in 0))
       (detect (pv-hainsworth-foote (fft* 0 source) 
				   1.0 
				   0.0
				   (mouse-x kr 0.01 1.0 1 0.1)
				   0.04)))
  (audition
   (out 0 (mul3 (sin-osc ar (mce2 440 445) 0)
		(decay (mul 0.1 detect) 0.1)
		0.1))))
]

Just Hainsworth metric, spot note transitions.


@racketblock[
(let* ((src (mul (lf-saw ar (mul-add (lf-noise0 kr 1) 90 400) 0) 0.5))
       (dtc (pv-hainsworth-foote (fft* 0 src)
				1.0
				0.0
				0.9
				0.5))
       (cmp (mul (sin-osc ar 440 0)
		 (decay (mul 0.1 dtc) 0.1))))
  (audition 
   (out 0 (mul (mce2 src cmp) 0.1))))
]

Just Foote metric.  Foote never triggers with threshold over 1.0,
threshold under mouse control.


@racketblock[
(let* ((src (sound-in 0))
       (dtc (pv-hainsworth-foote (fft* 0 src)
				0.0
				1.0
				(mouse-x kr 0.0 1.1 0 0.1)
				0.02))
       (cmp (mul (sin-osc ar 440 0)
		 (decay (mul 0.1 dtc) 0.1))))
  (audition 
   (out 0 (mul (mce2 src cmp) 0.1))))
]