--- libmpcodecs/vf_filmdint.c-save2	Sun Dec  7 19:18:09 2003
+++ libmpcodecs/vf_filmdint.c	Mon Dec  8 01:23:08 2003
@@ -1136,6 +1136,7 @@
     int dropped_fields = 0;
     double start_time, diff_time;
     char prev_chflag = p->chflag;
+    int keep_rate;
 
     if (!p->planes[0][0]) init(p, mpi);
 
@@ -1180,22 +1181,25 @@
     p->diff_time += diff_time - start_time;
     breaks = p->inframes ? find_breaks(p, s) : 2;
     p->inframes++;
+    keep_rate = 4*p->in_inc == p->out_dec;
 
     switch (breaks) {
       case 0:
       case 8:
       case 9:
       case 10:
-	if (p->notout < p->num_fields && p->iosync < 2*p->in_inc)
+	if (!keep_rate && p->notout < p->num_fields && p->iosync < 2*p->in_inc)
 	    break;
 	if (p->notout < p->num_fields)
 	    dropped_fields = -2;
       case 4:
-	if (p->iosync >= -2*p->in_inc)
+	if (keep_rate || p->iosync >= -2*p->in_inc)
 	    show_fields = (4<<p->num_fields)-1;
 	break;
       case 3:
-	if (p->iosync > 0) {
+	if (keep_rate)
+	    show_fields = 2;
+	else if (p->iosync > 0) {
 	    if (p->notout >= p->num_fields && p->iosync > 2*p->in_inc) {
 		show_fields = 4; /* prev odd only */
 		if (p->num_fields > 1)
@@ -1226,7 +1230,9 @@
 	    break;
 	}
       default:
-	if (p->notout >= p->num_fields &&
+	if (keep_rate)
+	    show_fields = 3 << (breaks & 1);
+	else if (p->notout >= p->num_fields &&
 	    p->iosync >= (breaks == 1 ? -p->in_inc :
 			  p->in_inc << (p->num_fields == 1))) {
 	    show_fields = (1 << (2 + p->num_fields)) - (1<<breaks);
@@ -1404,6 +1410,11 @@
 	if (args_remain) {
 	    mp_msg(MSGT_VFILTER, MSGL_FATAL,
 		   "filmdint: unknown suboption: %s\n", args_remain);
+	    return 0;
+	}
+	if (p->out_dec < p->in_inc) {
+	    mp_msg(MSGT_VFILTER, MSGL_FATAL,
+		   "filmdint: increasing the frame rate is not supported\n");
 	    return 0;
 	}
     }