http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2009-July/072472.html

--- vhook/imlib2.orig.c	2007-08-07 05:43:50.000000000 +0300
+++ vhook/imlib2.c	2009-07-07 08:20:59.935830867 +0300
@@ -84,12 +84,12 @@
     AVEvalExpr *eval_r, *eval_g, *eval_b, *eval_a;
     char *expr_R, *expr_G, *expr_B, *expr_A;
     int eval_colors;
-    double x, y;
+    double x, y, X, Y;
     char *fileImage;
     struct _CachedImage *cache;
     Imlib_Image imageOverlaid;
-    AVEvalExpr *eval_x, *eval_y;
-    char *expr_x, *expr_y;
+    AVEvalExpr *eval_x, *eval_y, *eval_X, *eval_Y;
+    char *expr_x, *expr_y, *expr_X, *expr_Y;
     int frame_number;
     int imageOverlaid_width, imageOverlaid_height;
 
@@ -123,6 +123,8 @@
         }
         ff_eval_free(ci->eval_x);
         ff_eval_free(ci->eval_y);
+        ff_eval_free(ci->eval_X);
+        ff_eval_free(ci->eval_Y);
         ff_eval_free(ci->eval_r);
         ff_eval_free(ci->eval_g);
         ff_eval_free(ci->eval_b);
@@ -130,6 +132,8 @@
 
         av_free(ci->expr_x);
         av_free(ci->expr_y);
+        av_free(ci->expr_X);
+        av_free(ci->expr_Y);
         av_free(ci->expr_R);
         av_free(ci->expr_G);
         av_free(ci->expr_B);
@@ -157,8 +161,12 @@
 
     ci->x = 0.0;
     ci->y = 0.0;
+    ci->X = 0.0;
+    ci->Y = 0.0;
     ci->expr_x = "0.0";
     ci->expr_y = "0.0";
+    ci->expr_X = "0.0";
+    ci->expr_Y = "0.0";
 
     optind = 0;
 
@@ -173,7 +181,7 @@
         imlib_add_path_to_font_path(fp);
 
 
-    while ((c = getopt(argc, argv, "R:G:B:A:C:c:f:F:t:x:y:i:")) > 0) {
+    while ((c = getopt(argc, argv, "R:G:B:A:C:c:f:F:t:x:y:i:X:Y:")) > 0) {
         switch (c) {
             case 'R':
                 ci->expr_R = av_strdup(optarg);
@@ -211,6 +219,12 @@
             case 'y':
                 ci->expr_y = av_strdup(optarg);
                 break;
+            case 'X':
+                ci->expr_X = av_strdup(optarg);
+                break;
+            case 'Y':
+                ci->expr_Y = av_strdup(optarg);
+                break;
             case 'i':
                 ci->fileImage = av_strdup(optarg);
                 break;
@@ -316,6 +330,16 @@
         ci->imageOverlaid_height = imlib_image_get_height();
     }
 
+    if (!(ci->eval_X = ff_parse(ci->expr_X, const_names, NULL, NULL, NULL, NULL, &error))){
+        av_log(NULL, AV_LOG_ERROR, "Couldn't parse X expression '%s': %s\n", ci->expr_X, error);
+        return -1;
+    }
+
+    if (!(ci->eval_Y = ff_parse(ci->expr_Y, const_names, NULL, NULL, NULL, NULL, &error))){
+        av_log(NULL, AV_LOG_ERROR, "Couldn't parse Y expression '%s': %s\n", ci->expr_Y, error);
+        return -1;
+    }
+
     if (!(ci->eval_x = ff_parse(ci->expr_x, const_names, NULL, NULL, NULL, NULL, &error))){
         av_log(NULL, AV_LOG_ERROR, "Couldn't parse x expression '%s': %s\n", ci->expr_x, error);
         return -1;
@@ -438,6 +462,8 @@
         ci->x = ff_parse_eval(ci->eval_x, const_values, ci);
         ci->y = ff_parse_eval(ci->eval_y, const_values, ci);
         y = ci->y;
+        ci->X = ff_parse_eval(ci->eval_X, const_values, ci);
+        ci->Y = ff_parse_eval(ci->eval_Y, const_values, ci);
 
         if (ci->eval_a) {
             ci->a = ff_parse_eval(ci->eval_a, const_values, ci);
@@ -464,10 +490,12 @@
         }
 
         if (ci->imageOverlaid) {
+			if (ci->X == 0) ci->X = ci->imageOverlaid_width;
+			if (ci->Y == 0) ci->Y = ci->imageOverlaid_height;
             imlib_context_set_image(image);
             imlib_blend_image_onto_image(ci->imageOverlaid, 0,
                 0, 0, ci->imageOverlaid_width, ci->imageOverlaid_height,
-                ci->x, ci->y, ci->imageOverlaid_width, ci->imageOverlaid_height);
+                ci->x, ci->y, ci->X, ci->Y);
         }
 
     }