Science in School

Science Day at Gerbert d'Orlhac school:

The desire to ask 'what would happen if?' is an innate quality that we all share. In many instances, satisfying this curiosity will require experiments to be designed and carried out, a process that is fundamental to almost all fields of research and innovation.

Experimentation is very much a hands-on activity that at school is usually associated with lessons in science and technology. Indeed, of the few memories we have of our lessons at school, many would involve some kind of science experiment such as growing crystals, building a radio, or looking at plants through a microsope.

We are "the innovation partners" - a group of people passionate about kindling the passion for science in schools

Gstreamer for Real Time priority tasks..

Since the support for Real-Time has been getting better and better in
linux, I propose that gstreamer should take advantage of this.
This would help pipelines with elements having time-critical or heavy
load where there is a demand for guaranteed cpu access.
This could be achieved by giving higher scheduling priority to such
plugins over others.

Hence, my proposal is to have a property called "priority" for all
elements. Then, pipelines like the following one could be launched:

gst-launch videotestsrc ! ffmpegcolorspace prio=90 ! xvimagesink

Here, the thread containing ffmpegcolorspace's buffer processing
method will get a higher priority than the rest.

Another example would be a camera capture plugin, where there is a
demand to capture frames with high accuracy.

A layered priority is also possible, as below.
gst-launch cameracapture prio=90 ! queue ! ffmpegcolorspace
prio=50 ! queue ! ffenc_h264 prio=50 ! ...


Implementation (I am sure there could be better ways, but this is what I tried):
----------------------------------------------------------------------------------------------------------------
The files modified are enclosed.

1. I installed a new property called prio in gst-object.c, after the
usual "name" property, in the method gst_object_class_init
Also, added a new field called _prio in gstobject class.
now all elements have prio property.


2. In gstpads.c, method gst_pad_push_event (GstPad * pad, GstEvent
* event) method of gstpads.c,

GstObject* objPar = (GstObject*) GST_OBJECT_PARENT (pad);
if(objPar->_prio!=0){
printf("########### Setting priority of '%s' running in
thread %x to %d ######## \n",
objPar->name,
pthread_self(),
objPar->_prio);

struct sched_param param;
memset(&param, 0, sizeof(sched_param));
param.sched_priority = objPar->_prio;
if(sched_setscheduler(0, SCHED_FIFO, &param) == -1) {
printf("error in setting priority >>>>>>>>>>> \n");
}
}

This applies priorities to the threads where the element's
processing function runs.


Questions
---------------
- Is such a mechanism of different priorities useful ?
I am testing some pipelines on machines that have high loads, and see
good improvement in the overall speed of the pipeline, compared to no
priority case.
However, it needs to be seen if it introduces additional complexity.
Has anybody tested something like this?
Please give some suggestions...

-Rosh