amp>u[t]</samp> is the current image. The current image can also be referenced by <samp>s</samp>. If the sequence number exceeds the length of the sequence, the count is wrapped. Thus in a 3-image sequence,  <samp>u[-1]</samp>, <samp>u[2]</samp>, and <samp>u[5]</samp> all refer to the same (third) image.</p>

<p>As an example, we form an image by averaging the first image and third images (the second (index 1) image is ignored and just junked):</p>

<pre class="p-3 mb-2 text-body-secondary bg-body-tertiary 