struct writer_node_group *setup_default_wng(void);
void print_writer_helps(int detailed);
struct writer_node *setup_writer_node(const char *arg, struct btr_node *parent);
+int get_btr_samplerate(struct btr_node *btrn, int32_t *result);
+int get_btr_channels(struct btr_node *btrn, int32_t *result);