nd = background + current/NBackFrames ;
0092     next(video);
0093 <span class="keyword">end</span>
0094 flipper = 256*ones(height, width).*mask;
0095 <span class="keyword">if</span> (strcmp(opt1,<span class="string">'neg'</span>) == 1)        <span class="comment">%make sure our fly will be a bright spot</span>
0096     background = -background+flipper;
0097 <span class="keyword">end</span>
0098 
0099 
0100 <span class="comment">%seek to StartFrame for tracking</span>
0101 seek(video,StartFrame);
0102 disp