title: ffmpeg capture streams in sync
body: <p>I'd like to capture multiple real-time video streams arriving on rtp protocol, using ffmpeg. When I initiate the recording, by issuing the <code>ffmpeg  &lt;command line parameters&gt;</code> command, it always takes a while for the connection to built up and the actual recording to begin. This might be more than 2 seconds in certain cases, which cause a constant time difference at the replay. </p>
  
  <p>How can I extract the information containing the time of the first actually recorded frame from ffmpeg? If it's not possible with ffmpeg without editing the source (which I did, and would like to avoid for other reasons), is there any similar multi-platform open-source tool which could be used?</p>