title: How to send a pointer on a callback function which is encapsulated in a class
body: <p>I'm actually coding a program in C++ using the library PortAudio.
  This library is using a callback function tu manage audio input and output.
  In C++, I implemented this callback function in my class "Audio" and I can't send it to Pa_OpenDefaultStream(). The compiler says "this argument is incompatible with parameter of type PaStreamCallback*" with this line :</p>
  
  <pre><code>Pa_OpenDefaultStream(&amp;this-&gt;_stream, 1, 2, paFloat32, this-&gt;_sampleRate, this-&gt;_framesPerBuffer, callbackFunction, NULL);
  </code></pre>
  
  <p>When I use C, sending my callbackFunction like this works well.
  How can I send my callback function to this OpenDefaultStream function ?</p>