+void register_writer_node(struct writer_node *wn, struct btr_node *parent,
+ struct sched *s);
+void get_btr_sample_rate(struct btr_node *btrn, int32_t *result);
+void get_btr_channels(struct btr_node *btrn, int32_t *result);
+void get_btr_sample_format(struct btr_node *btrn, int32_t *result);