title: CTC: What is the difference between space and blank?
body: <p>In the 2006 <a href="https://www.cs.toronto.edu/~graves/icml_2006.pdf" rel="nofollow noreferrer">article</a> about Connectionist Temporal Classification, Alex Graves &amp; co. introduced a model of decoding speech with <em>27</em> labels: 26 for the alphabet letters and one for <strong>blank</strong>, meaning no label (which I understand to be <strong>silence</strong>).</p>
  
  <p>However, I am seeing a lot of implementations of CTC that use <em>28</em> labels, one being the <strong>blank</strong> and another one being <strong>space</strong>. So far, I haven't been able to find an explanation for the need to use both these labels and, to me, they represent the same thing.</p>
  
  <p>Could you please explain the difference between blank and space in the context of CTC and why there's a need for both these labels?</p>