+static int get_btr_value(struct btr_node *btrn, const char *cmd,
+ int32_t *result)
+{
+ char *buf = NULL;
+ int ret = btr_exec_up(btrn, cmd, &buf);
+
+ *result = 0;
+ /*
+ * Errors may happen when the decoder returns EOF before the writer had
+ * a chance to query the buffer tree for the channel count, sample rate
+ * etc.
+ */
+ if (ret < 0)
+ return ret;
+ ret = para_atoi32(buf, result);
+ assert(ret >= 0);
+ free(buf);
+ return ret;
+}
+
+/**
+ * Ask parent btr nodes for the sample rate of the current stream.
+ *
+ * \param btrn Where to start the search.
+ * \param result Filled in by this function.
+ *
+ * \return Standard.
+ */
+int get_btr_sample_rate(struct btr_node *btrn, int32_t *result)
+{
+ return get_btr_value(btrn, "sample_rate", result);
+}
+
+/**
+ * Ask parent btr nodes for the channel count of the current stream.
+ *
+ * \param btrn See \ref get_btr_sample_rate.
+ * \param result See \ref get_btr_sample_rate.
+ *
+ * \return Standard.
+ */
+int get_btr_channels(struct btr_node *btrn, int32_t *result)
+{
+ return get_btr_value(btrn, "channels", result);
+}
+
+/**
+ * Ask parent btr nodes for the number of bits per sample and the byte sex.
+ *
+ * \param btrn See \ref get_btr_sample_rate.
+ * \param result Contains the sample format as an enum sample_format type.
+ *
+ * \return Standard.
+ */
+int get_btr_sample_format(struct btr_node *btrn, int32_t *result)