$Id$

= core profiling =

* scheduler keeps a list of usecs the process function of each element was
  running
* process functions are: loop, chain, get
* scheduler keeps a sum of all times
* each gst-element has a profile_percentage field

* when going to play
  * scheduler sets sum and all usecs in the list to 0
* when handling an element
  * remember old usecs t_old
  * take time t1
  * call elements processing function
  * take time t2
  * t_new=t2-t1
  * sum+=(t_new-t_old)
  * profile_percentage=t_new/sum;
  * should the percentage be averaged?
     * profile_percentage=(profile_percentage+(t_new/sum))/2.0;

* the profile_percentage shows how much CPU time the element uses in relation
  to the whole pipeline

= qos profiling =

* what data is needed ?
  * streamtime,propotion pairs from sinks
    draw a graph with gnuplot or similar
  * number of frames in total
  * number of frames dropped from each element that support QOS
    elements that don't support QOS wont have this information anyway

* idea1: parse data from debug log
   GST_QOS gstbasesink.c:1188:gst_base_sink_send_qos:<xvimagesink0> qos: proportion: 0.895615, diff -16437500, timestamp 0:00:09.208333333
  basesink gstbasesink.c:1542:gst_base_sink_render_object:<xvimagesink0> buffer late, dropping
  basesink gstbasesink.c:2534:gst_base_sink_change_state:<alsasink0> rendered: 1028, dropped: 0
   basesink gstbasesink.c:2534:gst_base_sink_change_state:<xvimagesink0> rendered: 598, dropped: 10

  + easy to do
  - debug log changes timing

* idea2: query data (via gst-launch)
  * add -r, --report option to gst-launch
  * send duration to get total number of frames (GST_FORMAT_DEFAULT for video is frames)
  * during playing we need to somehow listen to/capture/intercept QOS-events to record
    'streamtime,proportion' pairs
  * after EOS, send qos-queries to each element in the pipeline
    * qos-query will return:
      number of frames rendered
      number of frames dropped
    * print a nice table with the results
    
  + robust
  + also available to application
  - changes in core