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.

1 files changed, 2 insertions, 0 deletions

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,
 };