anchor.diff:                       (status-stream *standard-output*))
     (let* ((compute-available (make-string-hash-table))
            (host-args (make-string-hash-table))
  -         (work-queue (sort (frame-files directory) #'<
  -                           :key #'frame-number))
  +         (work-queue (sort-frames (frame-files directory)))
            (semaphore (sb-thread:make-semaphore :count 0))
            (n (length work-queue))
            (i 0))
  
positive.code: 
  
  (defun frame-number (item)
    (parse-integer (ppcre:regex-replace "^.*-([0-9]+).pov$" (namestring item) "\\1")))
  
  (defun net-render (&key
                       (directory *robray-tmp-directory*)
  
negative.code: (defun animate-encode (&key
                           (directory *robray-tmp-directory*)
                           (frames-per-second *frames-per-second*)
                           (pad 15)
                           (output-file "robray.mp4")
                           (video-codec "libx264"))
    ;; pad
    (let* ((images (directory  (concatenate 'string directory "/frame-*.png")))
           (last-frame-number (frame-number (car (last (sort-frames images))))))
      (map nil #'delete-file (directory  (concatenate 'string directory "/vframe-*.png")))
      (loop for file in images
         for n = (frame-number file)
         do (sb-ext:run-program "ln"
                                (list "-v"
                                      (namestring file)
                                      (format nil "vframe-~D.png" n))
                                :search t :wait t :directory directory
                                :output *standard-output*))
      (loop
         for i from 1 below pad
         for n = (+ i last-frame-number)
         ;until (zerop (mod n frames-per-second))
         do
           (sb-ext:run-program "cp"
                               (list "-v"
                                     (format nil "frame-~D.png" last-frame-number)
                                     (format nil "vframe-~D.png" n))
                               :search t :wait t :directory directory
                               :output *standard-output*)))
    ;; avconv -f image2 -r 30 -i frame-%d.png foo.mp4
    (let ((args (list "-f" "image2"
                      "-r" (write-to-string frames-per-second)
                      "-i" "vframe-%d.png"
                      "-codec:v" video-codec
                      "-loglevel" "warning"
                      "-y"
                      output-file)))
      (format t "~&avconv ~{~A ~}" args)
      (sb-ext:run-program "avconv"
                          args
                          :search t :wait t :directory directory
                          :output *standard-output*)
      (map nil #'delete-file (directory  (concatenate 'string directory "/vframe-*.png")))
      (format t "~&done")))
  
  
  (defun animate-render (&key
  