anchor.diff:  	     for j fixnum from 0
   	     until (= term +M_EOI+) do
   	       (when (/= (interpret-markers image term s) +M_SOS+)
  -		 (error "Unsupported marker in the frame header"))
  +		 (error 'unsupported-jpeg-frame-marker))
   	       (setf term (decode-scan image j s)))))
   
   (defun decode-stream (stream &optional buffer &key colorspace-conversion)
     "Return image array, height, width, and number of components. Does not support
   progressive DCT-based JPEGs."
     (unless (= (read-marker stream) +M_SOI+)
  -    (error "Unrecognized JPEG format"))
  +    (error 'unrecognized-file-format))
     (let* ((image (make-descriptor))
            (marker (interpret-markers image 0 stream)))
       (cond ((= +M_SOF0+ marker)
  
positive.code:         (setf term 0)
          (cond ((= #xe0 (logand #xf0 mk)) ; APPn marker
                 (read-app s))
                (t (cond ((= mk +M_DAC+) (error "Arithmetic encoding not supported"))
                         ((= mk +M_DRI+) (read-dri image s))
                         ((= mk +M_DHT+) (read-dht image s))
                         ((= mk +M_DQT+) (read-dqt image s))
  
negative.code:                                                   ((> y ylim)
                                                     (s16ref inbuf x ylim))
                                                    (t
                                                     (error 'internal-jpeg-encoder-error))
                                                     ))))))))
  
  ;;; Returns sum of Vi*Hi
  