lavfi: flag more dynamic i/o filters.

libavfilter/af_amerge.c

@@ -346,4 +346,5 @@ AVFilter avfilter_af_amerge = {
     .inputs        = NULL,
     .outputs       = amerge_outputs,
     .priv_class    = &amerge_class,
+    .flags         = AVFILTER_FLAG_DYNAMIC_INPUTS,
 };

libavfilter/avf_concat.c

@@ -419,4 +419,5 @@ AVFilter avfilter_avf_concat = {
     .inputs        = NULL,
     .outputs       = NULL,
     .priv_class    = &concat_class,
+    .flags         = AVFILTER_FLAG_DYNAMIC_INPUTS | AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };

libavfilter/f_ebur128.c

@@ -796,4 +796,5 @@ AVFilter avfilter_af_ebur128 = {
     .inputs        = ebur128_inputs,
     .outputs       = NULL,
     .priv_class    = &ebur128_class,
+    .flags         = AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };

libavfilter/src_movie.c

@@ -579,6 +579,7 @@ AVFilter avfilter_avsrc_movie = {
 
     .inputs    = NULL,
     .outputs   = NULL,
+    .flags     = AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };
 
 #endif  /* CONFIG_MOVIE_FILTER */
@@ -604,6 +605,7 @@ AVFilter avfilter_avsrc_amovie = {
     .inputs     = NULL,
     .outputs    = NULL,
     .priv_class = &amovie_class,
+    .flags      = AVFILTER_FLAG_DYNAMIC_OUTPUTS,
 };
 
 #endif /* CONFIG_AMOVIE_FILTER */