diff --git a/DIDLLite.py b/DIDLLite.py
index b8a9dbe..5fcdbb7 100644
--- a/DIDLLite.py
+++ b/DIDLLite.py
@@ -60,10 +60,36 @@ class Resource(object):
 		root.text = self.data
 
 		for i in self.attrs:
-			root.attrib[self.validattrs[i]] = str(self.attrs[i])
+			attr = self.validattrs[i]
+			value = self.attrs[i]
+			funname = 'format_%s' % attr
+			if hasattr(self, funname):
+				value = getattr(self, funname)(value)
+			else:
+				value = str(value)
+			assert isinstance(value, basestring), \
+			    'value is not a string: %s' % `value`
+			root.attrib[attr] = value
 
 		return root
 
+	@staticmethod
+	def format_duration(s):
+		if isinstance(s, basestring):
+			return s
+
+		# assume it is a number
+		s = abs(s)
+		secs = int(s)
+		frac = s - secs
+		minutes, secs = divmod(secs, 60)
+		hours, minutes = divmod(minutes, 60)
+		if frac:
+			frac = ('%.2f' % frac)[1:]
+		else:
+			frac = ''
+		return '%d:%02d:%02d%s' % (hours, minutes, secs, frac)
+
 class ResourceList(list):
 	'''Special class to not overwrite mimetypes that already exist.'''
 	def __init__(self, *args, **kwargs):
@@ -119,6 +145,8 @@ class Object(object):
 		    self.title)
 
 	def checkUpdate(self):
+		# It's tempting to call doUpdate here, but each object has to
+		# decide that.
 		pass
 
 	def toElement(self):
@@ -137,10 +165,11 @@ class Object(object):
 
 		if self.res is not None:
 			try:
-				for res in iter(self.res):
-					root.append(res.toElement())
-			except TypeError:
-				root.append(self.res.toElement())
+				resiter = iter(self.res)
+			except TypeError, x:
+				resiter = [ self.res ]
+			for res in resiter:
+				root.append(res.toElement())
 
 		if self.writeStatus is not None:
 			SubElement(root, 'upnp:writeStatus').text = self.writeStatus
@@ -159,9 +188,10 @@ class Item(Object):
 	refID = None
 	needupdate = True
 
-	def doUpdate(self):
-		# Update parent container
+	def doUpdate(self, child=False):
 		Container.doUpdate(self.cd[self.parentID])
+		# do NOT update parent container per 2.2.9 for
+		# ContainerUpdateID changes
 
 	def toElement(self):
 
@@ -325,11 +355,7 @@ class Container(Object, list):
 
 		raise NotImplementedError
 
-	def sort(self, fun=None):
-		if fun is None:
-			return list.sort(self, lambda x, y: cmp(x.title,
-			    y.title))
-
+	def sort(self, fun=lambda x, y: cmp(x.title, y.title)):
 		return list.sort(self, fun)
 
 	def doUpdate(self):
@@ -372,7 +398,12 @@ class Container(Object, list):
 				args = (children[i], )
 			else:
 				args = ()
-			#print 'i:', `i`, `isdict`, `args`, `self`
+			try:
+				#print 'i:', `i`, `isdict`, `args`, `self`
+				pass
+			except UnicodeEncodeError:
+				print 'i decode error'
+
 			klass, name, args, kwargs = self.createObject(i, *args)
 			if klass is not None:
 				self.cd.addItem(self.id, klass, name, *args,