title: How to create buffer, when i get RTSP stream by ffmpeg?
body: <p>I'm getting video stream from rtsp with ffmpeg on C. I'm writing it to file directly.
  I need to create 10 sec buffer, where i can hold last 10 sec video from rtsp sream. And at one moment i need to start record all video from rtsp to file (including this 10 sec buffer before).
  Can anybody tell me, how to do it?</p>