diff --git a/libavutil/tree.c b/libavutil/tree.c
index cce1d31090..0781453685 100644
--- a/libavutil/tree.c
+++ b/libavutil/tree.c
@@ -136,10 +136,11 @@ void av_tree_destroy(AVTreeNode *t){
 }
 
 #if 0
-void av_tree_enumerate(AVTreeNode *t, void *opaque, int (*f)(void *opaque, void *elem)){
-    int v= f(opaque, t->elem);
-    if(v>=0) av_tree_enumerate(t->child[0], opaque, f);
-    if(v<=0) av_tree_enumerate(t->child[1], opaque, f);
+void av_tree_enumerate(AVTreeNode *t, void *opaque, int (*cmp)(void *opaque, void *elem), int (*enu)(void *opaque, void *elem)){
+    int v= cmp ? cmp(opaque, t->elem) : 0;
+    if(v>=0) av_tree_enumerate(t->child[0], opaque, cmp, enu);
+    if(v==0) enu(opaque, t->elem);
+    if(v<=0) av_tree_enumerate(t->child[1], opaque, cmp, enu);
 }
 #endif