diff -Naur mplayer-b/libvo/vo_aa.c mplayer-c/libvo/vo_aa.c
--- mplayer-b/libvo/vo_aa.c	2011-03-07 10:40:02.000000000 +0200
+++ mplayer-c/libvo/vo_aa.c	2011-03-07 10:37:25.000000000 +0200
@@ -678,6 +678,9 @@
 
         /* initializing of aalib */
 
+    if (monitor_pixel_aspect == 1.0) {
+ 	monitor_pixel_aspect = 0.5;
+    }
     hidis=aa_getfirst(&aa_displayrecommended);
     if ( hidis==NULL ){
 	/* check /dev/vcsa<vt> */