anchor.diff:  (defconstant* +itunes-track-n+        (mk-mp4-atom-type #\t  #\r #\k #\n) "octet: yet another track number")
   (defconstant* +itunes-writer+         (mk-mp4-atom-type #xa9 #\w #\r #\t) "text: who wrote the song")
   (defconstant* +itunes-year+           (mk-mp4-atom-type #xa9 #\d #\a #\y) "text: year album was released")
  +
   (defconstant* +itunes-ilst-data+      (mk-mp4-atom-type #\d #\a #\t #\a)  "carries the actual data under an ilst atom")
   
   (defconstant* +m4-ftyp+               (mk-mp4-atom-type #\f #\t #\y #\p) "This should be the first atom type found in file")
  
positive.code:        (write-char (code-char ,(as-octet l3)) s)
         (write-char (code-char ,(as-octet l4)) s))))
  
  (defconstant* +root+                  (mk-mp4-atom-type #\R #\O #\O #\T)  "fake root for tree")
  (defconstant* +itunes-album+          (mk-mp4-atom-type #xa9 #\a #\l #\b) "text: album name")
  (defconstant* +itunes-album-artist+   (mk-mp4-atom-type #\a  #\A #\R #\T) "text: album artist")
  
negative.code:   (with-mp4-atom-slots (me)
      (stream-seek mp4-file (- atom-size 8) :current)))
  
  ;;; Atoms we need to implement someday... maybe
  (defclass atom----- (atom-skip) ())
  (defclass atom-akID (atom-skip) ())
  (defclass atom-apID (atom-skip) ())
  