lavfi: mark filters with dynamic number of inputs or outputs with special flags

This will be useful in avtools in the following commits.
Any other caller might also want to know this information.

6 files changed, 29 insertions, 0 deletions

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
@@ -373,6 +373,19 @@ 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,
 };