#!/usr/bin/sbcl --noinform
; If you haven't already, read about sbcl #! processing at
; http://sbcl.sf.net/manual/Unix_002dstyle-Command-Line-Protocol.html

; NOTE: This is obsolete!  Mplayer since 1.0_rc2 has a scaletempo audio filter.

; Usage: fastplay <factor> <mplayer-args ...>
;    eg: fastplay 2.1 moviefile.avi


(defun intersperse (thing list)
  "Put thing between each of the elements in list.
  (intersperse '|,| '(1 2 3)) => (1 |,| 2 |,| 3)"
  (rest (mapcan (lambda (x) (list thing x)) list)))

(defun decompose-to-factors-in-range (n min max)
  (cond ((< n min) (cons min (decompose-to-factors-in-range (* n min) min max)))
        ((> n max) (cons max (decompose-to-factors-in-range (* n min) min max)))
        (t (list n))))

(defun factor-to-semitones (factor) (* -12 (log factor 2)))

(defun tap-pitch-decorate (factor &key (path "/usr/lib/ladspa/tap_pitch.so")
                                       (dry  -40) 
                                       (wet    0))
  (format nil "ladspa=~A:tap_pitch:~A:0:~A:~A"
          path (factor-to-semitones factor) dry wet))

(defun build-tap-pitch-filter-chain (factor)
  (apply #'concatenate 'string
    (intersperse "," (mapcar #'tap-pitch-decorate
                             (decompose-to-factors-in-range factor 1/2 2)))))

(defun fastplay (factor &rest args)
  (sb-ext:run-program
    "mplayer" (append (list "-af" (build-tap-pitch-filter-chain
                                    (read-from-string factor))
                            "-speed" (format nil "~A" factor))
                      args)
    :output t
    :search t))

(apply #'fastplay (nthcdr 2 *posix-argv*))