avfilter: Deduplicate default video inputs/outputs

Lots of video filters use a very simple input or output:
An array with a single AVFilterPad whose name is "default"
and whose type is AVMEDIA_TYPE_VIDEO; everything else is unset.

Given that we never use pointer equality for inputs or outputs*,
we can simply use a single AVFilterPad instead of dozens; this
even saves .data.rel.ro (8312B here) as well as relocations.

*: In fact, several filters (like the filters in vf_lut.c)
already use the same outputs; furthermore, ff_filter_alloc()
duplicates the input and output pads so that we do not even
work with the pads directly.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/libavfilter/video.c b/libavfilter/video.c
index 7683ef6fd4..42eeb98c28 100644
--- a/libavfilter/video.c
+++ b/libavfilter/video.c
@@ -33,6 +33,13 @@
 #include "internal.h"
 #include "video.h"
 
+const AVFilterPad ff_video_default_filterpad[1] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    }
+};
+
 AVFrame *ff_null_get_video_buffer(AVFilterLink *link, int w, int h)
 {
     return ff_get_video_buffer(link->dst->outputs[0], w, h);