title: How much data was transmitted at a specific sink
body: <p>Having implemented a strange framework, I have to know how many bytes will be delivered at a specific tcpsink, before actually transmitting the data. (A rather large amount of data, actually. Some 100 megabytes.)</p>
  
  <ul>
  <li><p>I have separated audio and video data files (say Vorbis, AAC, Theora and h.264) and my "daemon" acts as a webservice that muxes the data together as requested. </p></li>
  <li><p>Unfortunately I need to deliver a correct Content-Length header and of cause there is no way of knowing the actual data amount that will be delivered unless you play the muxing process through at least once.</p></li>
  </ul>
  
  <p>My question is: Can I e.g. put an fakesink at the end of the pipe at the first run and query it, how many bytes it received? How would I query that?</p>
  
  <p>By now I use an fdsink and count the bytes I read, but I guess there is a better way. Is there a better way? :)</p>