@cclaunch
So, reading up a bit, it looks like you may need to assign that based on something like a pad id (a pad probe callback is suggested for this), but there seems to be no example of how to do that (at least from a grep of the source) and you’re right, it seems to contradict the docs. Also, if a pad id is used, the source id would be assigned by when it’s connected, which in the case of sometimes pads cannot be counted on to be identical every time.
I will investigate this on monday since it crosses purpose with what I’m doing right now. If I find all ids are 0 in my own pipeline, I’ll post here (and likewise will share my pipeline design if it works).