;; Strobe effect - holds frames for choppy look
;; @param frame_rate float [1, 60] default 12

(define-effect strobe
  ((frame_rate 12))
  (let* ((held (state-get 'held nil))
         (held-until (state-get 'held-until 0))
         (frame-duration (/ 1 frame_rate)))
    (if (or (= held nil) (>= t held-until))
        (begin
          (state-set 'held (copy frame))
          (state-set 'held-until (+ t frame-duration))
          frame)
        held)))