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;;; rubber.scm: rubber-sound stretches or contracts a sound (in time)
;;; (rubber-sound 1.5) makes it 50% longer
;;; rubber-sound looks for stable portions and either inserts or deletes periods
;;; period length is determined via autocorrelation
(provide 'snd-rubber.scm)
(define zeros-checked 8)
(define extension 10.0)
(define show-details #f)
;;; remove anything below 16Hz
;;; extend (src by 1/extension)
;;; collect upward zero-crossings
;;; collect weights for each across next zeros-checked crossings
;;; sort by least weight
;;; ramp (out or in) and check if done
(define rubber-sound
;; prepare sound (get rid of low freqs, resample)
(let ()
(define* (add-named-mark samp name snd chn)
(let ((m (add-mark samp snd chn)))
(set! (mark-name m) name)
m))
(define* (derumble-sound snd chn)
(let ((old-length (framples snd chn)))
(let ((fftlen (floor (expt 2 (ceiling (log (min old-length (srate snd)) 2)))))
(flt-env (list 0.0 0.0 (/ (* 2 16.0) (srate snd)) 0.0 (/ (* 2 20.0) (srate snd)) 1.0 1.0 1.0)))
(filter-sound flt-env fftlen snd chn)
(set! (framples snd chn) old-length))))
(define* (sample-sound snd chn)
(if (not (= extension 1.0))
(src-sound (/ 1.0 extension) 1.0 snd chn)))
(define* (unsample-sound snd chn)
;; undo earlier interpolation
(if (not (= extension 1.0))
(src-sound extension 1.0 snd chn)))
(define (crossings)
;; return number of upward zero crossings that don't look like silence
(let ((sr0 (make-sampler 0)))
(do ((samp0 (next-sample sr0))
(crosses 0)
(len (framples))
(sum 0.0)
(last-cross 0)
(silence (* extension .001))
(i 0 (+ i 1)))
((= i len)
crosses)
(let ((samp1 (next-sample sr0)))
(if (and (<= samp0 0.0)
(> samp1 0.0)
(> (- i last-cross) 4)
(> sum silence))
(begin
(set! crosses (+ crosses 1))
(set! last-cross i)
(set! sum 0.0)))
(set! sum (+ sum (abs samp0)))
(set! samp0 samp1)))))
(define (env-add s0 s1 samps)
(let ((data (make-float-vector samps))
(x 1.0)
(xinc (/ 1.0 samps))
(sr0 (make-sampler (floor s0)))
(sr1 (make-sampler (floor s1))))
(do ((i 0 (+ i 1)))
((= i samps))
(set! (data i) (+ (* x (next-sample sr0))
(* (- 1.0 x) (next-sample sr1))))
(set! x (+ x xinc)))
data))
(lambda* (stretch snd chn)
(as-one-edit
(lambda ()
(derumble-sound snd chn)
(sample-sound snd chn)
(let ((crosses (crossings)))
(let ((cross-samples (make-float-vector crosses))
(cross-weights (make-float-vector crosses))
(cross-marks (make-float-vector crosses))
(cross-periods (make-float-vector crosses)))
(let ((sr0 (make-sampler 0 snd chn))) ;; get cross points (sample numbers)
(do ((samp0 (next-sample sr0))
(len (framples))
(sum 0.0)
(last-cross 0)
(cross 0)
(silence (* extension .001))
(i 0 (+ i 1)))
((= i len))
(let ((samp1 (next-sample sr0)))
(if (and (<= samp0 0.0)
(> samp1 0.0)
(> (- i last-cross) 40)
(> sum silence))
(begin
(set! last-cross i)
(set! sum 0.0)
(set! (cross-samples cross) i)
(set! cross (+ cross 1))))
(set! sum (+ sum (abs samp0)))
(set! samp0 samp1))))
;; now run through crosses getting period match info
(do ((i 0 (+ i 1)))
((= i (- crosses 1)))
(let ((start (floor (cross-samples i)))
(autolen 0))
(let ((fftlen (floor (expt 2 (ceiling (log (* extension (/ (srate snd) 40.0)) 2))))))
(let ((len4 (/ fftlen 4))
(data (samples (floor start) fftlen)))
(autocorrelate data)
(set! autolen 0)
(do ((happy #f)
(j 1 (+ 1 j)))
((or happy (= j len4)))
(when (and (< (data j) (data (+ j 1)))
(> (data (+ j 1)) (data (+ j 2))))
(set! autolen (* j 2))
(set! happy #t)))))
(let* ((next-start (+ start autolen))
(min-i (+ i 1))
(min-samps (floor (abs (- (cross-samples min-i) next-start))))
(mink (min crosses (+ i zeros-checked))))
(do ((k (+ i 2) (+ k 1)))
((= k mink))
(let ((dist (floor (abs (- (cross-samples k) next-start)))))
(if (< dist min-samps)
(begin
(set! min-samps dist)
(set! min-i k)))))
(let ((current-mark min-i)
(current-min 0.0))
(let ((ampsum (make-one-pole 1.0 -1.0))
(diffsum (make-one-pole 1.0 -1.0)))
(do ((sr0 (make-sampler (floor start)))
(sr1 (make-sampler (floor (cross-samples current-mark))))
(samp0 0.0)
(i 0 (+ i 1)))
((= i autolen))
(set! samp0 (next-sample sr0))
(one-pole ampsum (abs samp0))
(one-pole diffsum (abs (- (next-sample sr1) samp0))))
(set! diffsum (one-pole diffsum 0.0))
(set! ampsum (one-pole ampsum 0.0))
(set! current-min (if (= diffsum 0.0) 0.0 (/ diffsum ampsum))))
(set! min-samps (round (* 0.5 current-min)))
(do ((top (min (- crosses 1) current-mark (+ i zeros-checked)))
(k (+ i 1) (+ k 1))
(wgt 0.0 0.0))
((= k top))
(let ((ampsum (make-one-pole 1.0 -1.0))
(diffsum (make-one-pole 1.0 -1.0)))
(do ((sr0 (make-sampler (floor start)))
(sr1 (make-sampler (floor (cross-samples k))))
(samp0 0.0)
(i 0 (+ i 1)))
((= i autolen))
(set! samp0 (next-sample sr0))
(one-pole ampsum (abs samp0))
(one-pole diffsum (abs (- (next-sample sr1) samp0))))
(set! diffsum (one-pole diffsum 0.0))
(set! ampsum (one-pole ampsum 0.0))
(set! wgt (if (= diffsum 0.0) 0.0 (/ diffsum ampsum))))
(if (< wgt min-samps)
(begin
(set! min-samps (floor wgt))
(set! min-i k))))
(if (not (= current-mark min-i))
(set! (cross-weights i) 1000.0) ; these are confused, so effectively erase them
(begin
(set! (cross-weights i) current-min)
(set! (cross-marks i) current-mark)
(set! (cross-periods i) (- (cross-samples current-mark) (cross-samples i)))
))))))
;; now sort weights to scatter the changes as evenly as possible
(let ((len (framples snd chn)))
(let ((adding (> stretch 1.0))
(samps (floor (* (abs (- stretch 1.0)) len)))
(weights (length cross-weights)))
(let ((needed-samps (if adding samps (min len (* samps 2))))
(handled 0)
(mult 1)
(curs 0)
(eds (make-float-vector weights)))
(do ((best-mark -1 -1)
(old-handled handled handled))
((or (= curs weights) (>= handled needed-samps)))
;; need to find (more than) enough splice points to delete samps
(let ((cur 0)
(curmin (cross-weights 0))
(len (length cross-weights)))
(do ((i 0 (+ i 1)))
((= i len))
(if (< (cross-weights i) curmin)
(begin
(set! cur i)
(set! curmin (cross-weights i)))))
(set! best-mark cur))
(set! handled (+ handled (floor (cross-periods best-mark))))
(if (or (< handled needed-samps)
(< (- handled needed-samps) (- needed-samps old-handled)))
(begin
(set! (eds curs) best-mark)
(set! curs (+ 1 curs))))
(set! (cross-weights best-mark) 1000.0))
(if (>= curs weights)
(set! mult (ceiling (/ needed-samps handled))))
(do ((changed-len 0)
(weights (length cross-weights))
(i 0 (+ i 1)))
((or (= i curs)
(> changed-len samps))
(if show-details
(snd-print (format #f "wanted: ~D, got ~D~%" (floor samps) (floor changed-len)))))
(let* ((best-mark (floor (eds i)))
(beg (floor (cross-samples best-mark)))
(next-beg (floor (cross-samples (floor (cross-marks best-mark)))))
(len (floor (cross-periods best-mark))))
(when (> len 0)
(if adding
(let ((new-samps
(env-add beg next-beg len)))
(if show-details
(add-named-mark beg (format #f "~D:~D" i (floor (/ len extension)))))
(insert-samples beg len new-samps)
(if (> mult 1)
(do ((k 1 (+ k 1)))
((= k mult))
(insert-samples (+ beg (* k len)) len new-samps)))
(set! changed-len (+ changed-len (* mult len)))
(do ((j 0 (+ 1 j)))
((= j weights))
(let ((curbeg (floor (cross-samples j))))
(if (> curbeg beg)
(set! (cross-samples j) (+ curbeg len))))))
(begin
(if (>= beg (framples))
(snd-print (format #f "trouble at ~D: ~D of ~D~%" i beg (framples))))
(if show-details
(add-named-mark (- beg 1) (format #f "~D:~D" i (floor (/ len extension)))))
(delete-samples beg len)
(set! changed-len (+ changed-len len))
(do ((end (+ beg len))
(j 0 (+ 1 j)))
((= j weights))
(let ((curbeg (floor (cross-samples j))))
(if (> curbeg beg)
(if (< curbeg end)
(set! (cross-periods j) 0)
(set! (cross-samples j) (- curbeg len)))))))))))
)))))
;; and return to original srate
(unsample-sound snd chn)
(if show-details
(snd-print (format #f "~A -> ~A (~A)~%" (framples snd chn 0) (framples snd chn) (floor (* stretch (framples snd chn 0))))))
) ; end of as-one-edit thunk
(format #f "rubber-sound ~A" stretch)))))
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