From 531d09fb2d6bddb968dbef1fbb8b351aed85cbfa Mon Sep 17 00:00:00 2001
From: Nicolas George <george@nsup.org>
Date: Sat, 19 Feb 2022 16:13:39 +0100
Subject: [PATCH] lavfi: add ff_inoutlink_check_flow()

---
 libavfilter/avfilter.c | 8 ++++++++
 libavfilter/filters.h  | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 7362bcdab5..1f37a70179 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -1559,6 +1559,14 @@ int ff_outlink_get_status(AVFilterLink *link)
     return link->status_in;
 }
 
+int ff_inoutlink_check_flow(AVFilterLink *inlink, AVFilterLink *outlink)
+{
+    return ff_outlink_frame_wanted(outlink) ||
+           ff_inlink_check_available_frame(inlink) ||
+           inlink->status_out;
+}
+
+
 const AVClass *avfilter_get_class(void)
 {
     return &avfilter_class;
diff --git a/libavfilter/filters.h b/libavfilter/filters.h
index 1157755403..86bc49d459 100644
--- a/libavfilter/filters.h
+++ b/libavfilter/filters.h
@@ -258,4 +258,12 @@ static inline void ff_outlink_set_status(AVFilterLink *link, int status, int64_t
     } \
 } while (0)
 
+/**
+ * Check for flow control between input and output.
+ * This is necessary for filters that may produce several output frames for
+ * a single input event, otherwise they may produce them all at once,
+ * causing excessive memory consumption.
+ */
+int ff_inoutlink_check_flow(AVFilterLink *inlink, AVFilterLink *outlink);
+
 #endif /* AVFILTER_FILTERS_H */