diff --git a/doc/APIchanges b/doc/APIchanges
index 35c49f6ddd..87a472b679 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -22,6 +22,7 @@ API changes, most recent first:
   filter.
   Add avfilter_init_str(), deprecate avfilter_init_filter().
   Add avfilter_init_dict().
+  Add AVFilter.flags field and AVFILTER_FLAG_DYNAMIC_{INPUTS,OUTPUTS} flags.
 
 2013-xx-xx - lavfi 3.7.0 - avfilter.h
   Add AVFilter.priv_class for exporting filter options through the AVOptions API
diff --git a/libavfilter/af_amix.c b/libavfilter/af_amix.c
index f7f003b6b1..6bc74585c7 100644
--- a/libavfilter/af_amix.c
+++ b/libavfilter/af_amix.c
@@ -562,4 +562,6 @@ AVFilter avfilter_af_amix = {
 
     .inputs    = NULL,
     .outputs   = avfilter_af_amix_outputs,
+
+    .flags     = AVFILTER_FLAG_DYNAMIC_INPUTS,
 };
diff --git a/libavfilter/af_channelsplit.c b/libavfilter/af_channelsplit.c
index fcdc34eca0..fde5985bf3 100644
--- a/libavfilter/af_channelsplit.c
+++ b/libavfilter/af_channelsplit.c
@@ -149,4 +149,6 @@ AVFilter avfilter_af_channelsplit = {
 
     .inputs  = avfilter_af_channelsplit_inputs,
     .outputs = NULL,
+
+    .flags   = AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };
diff --git a/libavfilter/af_join.c b/libavfilter/af_join.c
index a06812ed32..02bc8c8f14 100644
--- a/libavfilter/af_join.c
+++ b/libavfilter/af_join.c
@@ -522,4 +522,6 @@ AVFilter avfilter_af_join = {
 
     .inputs  = NULL,
     .outputs = avfilter_af_join_outputs,
+
+    .flags   = AVFILTER_FLAG_DYNAMIC_INPUTS,
 };
diff --git a/libavfilter/avfilter.h b/libavfilter/avfilter.h
index dffb2e56d9..dd29ec0564 100644
--- a/libavfilter/avfilter.h
+++ b/libavfilter/avfilter.h
@@ -372,6 +372,19 @@ const char *avfilter_pad_get_name(const AVFilterPad *pads, int pad_idx);
  */
 enum AVMediaType avfilter_pad_get_type(const AVFilterPad *pads, int pad_idx);
 
+/**
+ * The number of the filter inputs is not determined just by AVFilter.inputs.
+ * The filter might add additional inputs during initialization depending on the
+ * options supplied to it.
+ */
+#define AVFILTER_FLAG_DYNAMIC_INPUTS        (1 << 0)
+/**
+ * The number of the filter outputs is not determined just by AVFilter.outputs.
+ * The filter might add additional outputs during initialization depending on
+ * the options supplied to it.
+ */
+#define AVFILTER_FLAG_DYNAMIC_OUTPUTS       (1 << 1)
+
 /**
  * Filter definition. This defines the pads a filter contains, and all the
  * callback functions used to interact with the filter.
@@ -394,6 +407,11 @@ typedef struct AVFilter {
      */
     const AVClass *priv_class;
 
+    /**
+     * A combination of AVFILTER_FLAG_*
+     */
+    int flags;
+
     /*****************************************************************
      * All fields below this line are not part of the public API. They
      * may not be used outside of libavfilter and can be changed and
diff --git a/libavfilter/split.c b/libavfilter/split.c
index 7e8b4cc24f..8c03de5b17 100644
--- a/libavfilter/split.c
+++ b/libavfilter/split.c
@@ -129,6 +129,8 @@ AVFilter avfilter_vf_split = {
 
     .inputs    = avfilter_vf_split_inputs,
     .outputs   = NULL,
+
+    .flags     = AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };
 
 static const AVFilterPad avfilter_af_asplit_inputs[] = {
@@ -153,4 +155,6 @@ AVFilter avfilter_af_asplit = {
 
     .inputs  = avfilter_af_asplit_inputs,
     .outputs = NULL,
+
+    .flags   = AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };