Stian Selnes authored Oct 29, 2015 and Sebastian Dröge committed Nov 01, 2016

It's useful to be able to set a name pattern for GST_DEBUG_FILE so that
the same environment variable can be used for multiple processes and
still write to different files. Especially useful if these processes
run simultaneously.

%p: Replaced with PID
%r: Replaced with random number

%p is obviously useful. %r is useful when for instance running two
processes with same PID but in different containers.

https://bugzilla.gnome.org/show_bug.cgi?id=773092