title: FFMPEG avformat_open_input returned error
body: <p>Sorry I have to ask this question, but I couldn't find a reference to the return codes of avformat_open_input, and I couldn't find anyone asking/answering about mine.</p>
  
  <p>After this call to the function</p>
  
  <pre><code>err = avformat_open_input(&amp;pFormatCtx, is-&gt;filename, NULL, NULL);
  </code></pre>
  
  <p>I get err = -13. What does it mean, and if anybody answers, please also share how you know which code corresponds to which error.</p>
  
  <p>UPDATE:
  OK, I finally figured out how to turn the code into a message, and the message is "Permission denied". Does anyone have an idea where the problem with this might be?</p>