9 <span class="keyword">if</span> (nargin == 2)
0020     numFrames = lf - ff + 1 - startAt + 1;
0021 <span class="keyword">end</span>
0022 <span class="keyword">if</span> ((startAt &lt; ff) || startAt &gt; lf)
0023     error(<span class="string">'btk:CropAcquisiton'</span>,<span class="string">'Invalid index.'</span>);
0024 <span class="keyword">elseif</span> (numFrames &gt; lf - startAt + 1)
0025     error(<span class="string">'btk:CropAcquisiton'</span>,<span class="string">'Incorrect number of frames spe