+/** @brief Child-process half of prepare()
+ * @return Process exit code
+ *
+ * Called in subprocess to execute the decoder for a raw-format player.
+ *
+ * @todo We currently run the normalizer from here in a double-fork. This is
+ * unsatisfactory for many reasons: we can't prevent it outliving the main
+ * server and we don't adequately report its exit status.
+ */