title: Timestamping in Gstreamer pipeline
body: <p>I have created a gstreamer pipeline with my appsrc;
  the pipeline is like this</p>
  
  <pre><code>appsrc name=src ! video/x-h264 ! decodebin ! queue ! autovideosink 
  </code></pre>
  
  <p>I have written code to run this pipeline;
  I will get h264 frames in my appsrc, and I am pushing it to decodebin. I am not receiving any timestamps in my appsrc. So I am thinking of feeding timestamps values (such that the fps will be 30fps). 
  There are two feilds in the GstBuffer Structure, the <code>timestamp</code> feild and the <code>PTS</code> feild,
  which one should I set with my timestamp. And on reference to which clock the render and decoder will check these timestamps ?</p>
  
  <p>Currently wht I am doing is creating a baseclock reference from system time, and with respect to that time I am incrementing my timestamps, and it is not working, If I set only the duration feild it plays fine, But I want to implement the timestamp logic so that the decoder can drop some frames if some comes late.. I have very little knowledge about timestamping, so I want to know more about timestamping</p>