fftools/ffmpeg_filter: reject filtergraphs with zero outputs

Nothing useful can be done with them currently.

1 files changed, 6 insertions, 0 deletions

diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index 4f7565e44e..54c7ed1f5c 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -845,6 +845,12 @@ FilterGraph *fg_create(char *graph_desc)
         ofilter->name      = describe_filter_link(fg, cur, 0);
     }
 
+    if (!fg->nb_outputs) {
+        av_log(fg, AV_LOG_FATAL, "A filtergraph has zero outputs, this is not supported\n");
+        ret = AVERROR(ENOSYS);
+        goto fail;
+    }
+
 fail:
     avfilter_inout_free(&inputs);
     avfilter_inout_free(&outputs);