diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 30a63fa62c..c2a50221a8 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -26,6 +26,12 @@
  */
 void av_register_all(void)
 {
+    static int inited = 0;
+    
+    if (inited != 0)
+        return;
+    inited = 1;
+
     avcodec_init();
     avcodec_register_all();