+/* Called from the main thread, from source-output.c only. The normal way to
+ * set the source reference volume is to call pa_source_set_volume(), but the
+ * flat volume logic in source-output.c needs also a function that doesn't do
+ * all the extra stuff that pa_source_set_volume() does. This function simply
+ * sets s->reference_volume and fires change notifications. */
+void pa_source_set_reference_volume_direct(pa_source *s, const pa_cvolume *volume);
+