oggenc instances started in the same second generate the same serial number
Two copies of oggenc that start in the same second will generate output with the same serial number, which is a problem if the user wants to concatenate 2 or more of the output files (since all streams in a file must have unique serial numbers). These commands show the duplicate numbers:
$ dd if=/dev/urandom of=test.raw bs=4 count=44100
$ for x in {0..9} ; do oggenc -q5 --raw test.raw -o test$x.ogg; done
$ ogginfo test?.ogg |grep serial
This happens because the random number generator is only seeded using the time. XORing the time with the PID fixes this problem, though I'm not sure whether getpid() is available on all platforms.