title: libavcodec's AVRational vs 29.9 fps
body: <p>So the AVCodecContext structure has a nice little member named time_base which is used to represent frames per second when encoding video, which is what I'm doing. time_base is an AVRational structure which consists of a numerator (num) and a denominator (den). I'm not good at math and so the only rational number I can think of for 29.9 is 29 and 9/10, which doesn't work. What should I fill num and den with?  </p>
  
  <p>p.s the answer is not 299/10</p>