anchor.diff:         (write-char (code-char ,(as-octet l3)) s)
          (write-char (code-char ,(as-octet l4)) s))))
   
  +;;;; Atom names/ids
   (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")
  
positive.code: (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")
  
negative.code: (defclass atom-xid  (atom-skip) ()) ; NOTE: it's actually "xid#\Space"
  
  (defclass mp4-container-atom (mp4-atom)
    ((tree :accessor tree :documentation "Note: this is ONLY set for the ROOT atom"))
    (:documentation "An atom that 'contains' other atoms"))
  
  (defmethod initialize-instance :after ((me mp4-container-atom) &key mp4-file &allow-other-keys)
    (declare #.utils:*standard-optimize-settings*)
  