diff -urN rt_v26/img.py rt_v27/img.py
--- rt_v26/img.py	2018-04-20 23:52:43.000000000 +0900
+++ rt_v27/img.py	2018-04-22 21:50:00.000000000 +0900
@@ -57,22 +57,45 @@
 	fps = dic.get('fps')
 	n = dic.get('n')
 
+	def err_recover():
+		if vc.isOpened():
+			vc.open(fn)
+			if 'img' in dic:
+				dic.pop('img')
+		if get_prop('i') != 0:
+			set_prop('i', 0)
+
+	# get_prop(7) is doubt
+	for i in range(n):
+		(ret, _) = vc.read()
+		if not ret or len(_) == 0:
+			dic['n'] = n = i
+			break
+	err_recover()
+
 	def img_idx(i):
 		i %= n # loop
-		if dic.get('i') != i:
-			set_prop('i', i)
+		if 'img' in dic and dic.get('i') != i:
+			dic.pop('img')
+			if dic.get('i')+1 != i:
+				set_prop('i', i)
 			dic['i'] = i
-			if 'img' in dic:
-				dic.pop('img')
 		if 'img' not in dic:
 			( ret, dic['img'] ) = vc.read()
+			if not ret:
+				err_recover()
+				for j in range(i+1):
+					( ret, dic['img'] ) = vc.read()
+					if not ret:
+						sys.stderr.write( 'err {} {}/{}\n'.format( fn, j, dic.get('n') ) )
+				dic['i'] = i
 		return dic.get('img')
 	dic['img_idx'] = img_idx
 
 	sec_to_i = lambda sec: int(fps * sec)
 	dic['img_sec'] = lambda sec: img_idx( sec_to_i(sec) )
 
-	dic['imgs'] = lambda : map( img_idx, range(n) ) # func
+	dic['imgs'] = lambda : ut.map_lst( img_idx, range(n) ) # func
 
 	return dic