Keep video IDs verbatim if possible (Closes #571)

3 files changed, 21 insertions, 11 deletions

diff --git a/test/test_utils.py b/test/test_utils.py
index fd8190f51..8afc30370 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -79,6 +79,11 @@ class TestUtil(unittest.TestCase):
         self.assertTrue(sanitize_filename('-', restricted=True) != '')
         self.assertTrue(sanitize_filename(':', restricted=True) != '')
 
+    def test_sanitize_ids(self):
+        self.assertEquals(sanitize_filename('_n_cd26wFpw', is_id=True), '_n_cd26wFpw')
+        self.assertEquals(sanitize_filename('_BD_eEpuzXw', is_id=True), '_BD_eEpuzXw')
+        self.assertEquals(sanitize_filename('N0Y__7-UOdI', is_id=True), 'N0Y__7-UOdI')
+
     def test_ordered_set(self):
         self.assertEqual(orderedSet([1, 1, 2, 3, 4, 4, 5, 6, 7, 3, 5]), [1, 2, 3, 4, 5, 6, 7])
         self.assertEqual(orderedSet([]), [])
diff --git a/youtube_dl/FileDownloader.py b/youtube_dl/FileDownloader.py
index 48c8eb126..c471cc160 100644
--- a/youtube_dl/FileDownloader.py
+++ b/youtube_dl/FileDownloader.py
@@ -334,8 +334,11 @@ class FileDownloader(object):
             template_dict['epoch'] = int(time.time())
             template_dict['autonumber'] = u'%05d' % self._num_downloads
 
-            template_dict = dict((key, u'NA' if val is None else val) for key, val in template_dict.items())
-            template_dict = dict((k, sanitize_filename(compat_str(v), self.params.get('restrictfilenames'))) for k,v in template_dict.items())
+            sanitize = lambda k,v: sanitize_filename(
+                u'NA' if v is None else compat_str(v),
+                restricted=self.params.get('restrictfilenames'),
+                is_id=(k==u'id'))
+            template_dict = dict((k, sanitize(k, v)) for k,v in template_dict.items())
 
             filename = self.params['outtmpl'] % template_dict
             return filename
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 7f73b8476..4dcf18991 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -317,9 +317,10 @@ def timeconvert(timestr):
         timestamp = email.utils.mktime_tz(timetuple)
     return timestamp
 
-def sanitize_filename(s, restricted=False):
+def sanitize_filename(s, restricted=False, is_id=False):
     """Sanitizes a string so it could be used as part of a filename.
     If restricted is set, use a stricter subset of allowed characters.
+    Set is_id if this is not an arbitrary string, but an ID that should be kept if possible
     """
     def replace_insane(char):
         if char == '?' or ord(char) < 32 or ord(char) == 127:
@@ -337,14 +338,15 @@ def sanitize_filename(s, restricted=False):
         return char
 
     result = u''.join(map(replace_insane, s))
-    while '__' in result:
-        result = result.replace('__', '_')
-    result = result.strip('_')
-    # Common case of "Foreign band name - English song title"
-    if restricted and result.startswith('-_'):
-        result = result[2:]
-    if not result:
-        result = '_'
+    if not is_id:
+        while '__' in result:
+            result = result.replace('__', '_')
+        result = result.strip('_')
+        # Common case of "Foreign band name - English song title"
+        if restricted and result.startswith('-_'):
+            result = result[2:]
+        if not result:
+            result = '_'
     return result
 
 def orderedSet(iterable):