anchor.diff:  	(wcursor rec) (cdr (chunk-queue rec))))
   
   (defclass audio-stream-record (stream-record)
  -  ())
  +  ((compression-code :accessor compression-code)
  +   (number-of-channels :accessor number-of-channels)
  +   (sample-rate :accessor sample-rate)
  +   (average-bytes-per-second :accessor average-bytes-per-second)
  +   (block-align :accessor block-align)
  +   (significant-bits-per-sample :accessor significant-bits-per-sample)
  +   (extra-format-bytes :accessor extra-format-bytes)
  +   (extra-bytes :accessor extra-bytes)))
   
   (defmethod shared-initialize :after ((rec audio-stream-record) slots &key &allow-other-keys)
     (declare (ignorable slots))
  
positive.code: 	 (error 'unsupported-avi-file-format))
         (cond ((and (string-equal (fcc-type rec) "vids") (string-equal (fcc-handler rec) "mjpg"))
  	      (change-class rec 'mjpeg-stream-record))
  	     ((string-equal (fcc-type rec) "auds") (change-class rec 'audio-stream-record)))
         (return-from read-avi-stream-info rec))
    (error 'malformed-avi-file-format))
  
  
negative.code:   (setf (cdr (last (chunk-queue rec))) (chunk-queue rec)
  	(rcursor rec) (chunk-queue rec)
  	(wcursor rec) (cdr (chunk-queue rec))))
  
  (defmethod read-audio-stream-header ((rec audio-stream-record) stream)
    (loop for chunk = (riff:read-riff-chunk stream)
       when (string-equal (riff:riff-chunk-id chunk) "strf") do
         (flexi-streams:with-input-from-sequence (is (riff:riff-chunk-data chunk))
  	(setf (compression-code rec) (riff:read-u2 is)
  	     (number-of-channels rec) (riff:read-u2 is)
  	     (sample-rate rec) (riff:read-u4 is)
  	     (average-bytes-per-second rec) (riff:read-u4 is)
  	     (block-align rec) (riff:read-u2 is)
  	     (significant-bits-per-sample rec) (riff:read-u2 is))
         (unless (eql (compression-code rec) 1)
  	 (setf (extra-format-bytes rec) (riff:read-u2 is)
  	       (extra-bytes rec) (make-array (extra-format-bytes rec) :element-type (stream-element-type is)))
  	 (read-sequence (extra-bytes rec) is)))
         (return)))
  
  (defclass video-stream ()
    ((filename :accessor filename :initarg :filename :initform nil)))
  