title: opencv multi channel matrix
body: <p>I want to create a vector of matrices which each cell of a matrix is a 2 element vector.
  I tried to use this code but it gets stuck on assignment.</p>
  
  <pre><code>typedef Vec&lt;char, 2&gt; Vec2u;
  
  Mat VecMat[8];
  VecMat[0].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[1].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[2].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[3].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[4].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[5].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[6].create(FrameHeight, FrameWidth, CV_8UC2);
  VecMat[7].create(FrameHeight, FrameWidth, CV_8UC2);
  
  Vec2u elem;
  elem[0] = num1;
  elem[1] = num2;
  VecMat[2].at&lt;Vec2u&gt;(row,col) = elem;
  </code></pre>
  
  <p>Any ideas why???
  Thanks</p>