diff --git a/libavfilter/filters.h b/libavfilter/filters.h
index 86bc49d459..69411d3aa7 100644
--- a/libavfilter/filters.h
+++ b/libavfilter/filters.h
@@ -266,4 +266,19 @@ static inline void ff_outlink_set_status(AVFilterLink *link, int status, int64_t
  */
 int ff_inoutlink_check_flow(AVFilterLink *inlink, AVFilterLink *outlink);
 
+/**
+ * Compute the boundary index for a slice when work of size total is split
+ * into nb_jobs slices. Returns the first index of slice jobnr, so the slice
+ * jobnr covers [ff_slice_pos(total, jobnr, nb_jobs),
+ * ff_slice_pos(total, jobnr + 1, nb_jobs)).
+ *
+ * The multiplication is performed in 64bit to avoid signed overflow of the
+ * total * jobnr intermediate that would occur for large dimensions and many
+ * slice threads.
+ */
+static inline int ff_slice_pos(int total, int jobnr, int nb_jobs)
+{
+    return (int)((int64_t)total * jobnr / nb_jobs);
+}
+
 #endif /* AVFILTER_FILTERS_H */