1 files changed, 18 insertions, 1 deletions
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index d00b14b86..c0325f054 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -925,6 +925,21 @@ def determine_ext(url, default_ext='unknown_video'):
     guess = url.partition('?')[0].rpartition('.')[2]
     if re.match(r'^[A-Za-z0-9]+$', guess):
         return guess
+    elif guess.rstrip('/') in (
+            'mp4', 'm4a', 'm4p', 'm4b', 'm4r', 'm4v', 'aac',
+            'flv', 'f4v', 'f4a', 'f4b',
+            'webm', 'ogg', 'ogv', 'oga', 'ogx', 'spx', 'opus',
+            'mkv', 'mka', 'mk3d',
+            'avi', 'divx',
+            'mov',
+            'asf', 'wmv', 'wma',
+            '3gp', '3g2',
+            'mp3',
+            'flac',
+            'ape',
+            'wav',
+            'f4f', 'f4m', 'm3u8', 'smil'):
+        return guess.rstrip('/')
     else:
         return default_ext
 
@@ -1668,7 +1683,9 @@ def urlencode_postdata(*args, **kargs):
 
 
 def encode_dict(d, encoding='utf-8'):
-    return dict((k.encode(encoding), v.encode(encoding)) for k, v in d.items())
+    def encode(v):
+        return v.encode(encoding) if isinstance(v, compat_basestring) else v
+    return dict((encode(k), encode(v)) for k, v in d.items())
 
 
 US_RATINGS = {