--- /dev/null
+--- a/libavfilter/formats.c
++++ b/libavfilter/formats.c
+@@ -110,11 +110,13 @@
+ possibly causing a lossy conversion elsewhere in the graph.
+ To avoid that, pretend that there are no common formats to force the
+ insertion of a conversion filter. */
+- if (type == AVMEDIA_TYPE_VIDEO)
++ if (type == AVMEDIA_TYPE_VIDEO) {
+ for (i = 0; i < a->nb_formats; i++) {
+ const AVPixFmtDescriptor *const adesc = av_pix_fmt_desc_get(a->formats[i]);
++ if( !adesc ) continue;
+ for (j = 0; j < b->nb_formats; j++) {
+ const AVPixFmtDescriptor *bdesc = av_pix_fmt_desc_get(b->formats[j]);
++ if( !bdesc ) continue;
+ alpha2 |= adesc->flags & bdesc->flags & AV_PIX_FMT_FLAG_ALPHA;
+ chroma2|= adesc->nb_components > 1 && bdesc->nb_components > 1;
+ if (a->formats[i] == b->formats[j]) {
+@@ -123,6 +125,7 @@
+ }
+ }
+ }
++ }
+
+ // If chroma or alpha can be lost through merging then do not merge
+ if (alpha2 > alpha1 || chroma2 > chroma1)