YoutubeIE: fallback to automatic captions when subtitles aren't found (closes #843)

Also modify test_youtube_subtitles to support running the tests in any order.

test/test_youtube_subtitles.py

@@ -28,7 +28,9 @@ compat_urllib_request.install_opener(opener)
 class FakeDownloader(FileDownloader):
     def __init__(self):
         self.result = []
-        self.params = parameters
+        # Different instances of the downloader can't share the same dictionary
+        # some test set the "sublang" parameter, which would break the md5 checks.
+        self.params = dict(parameters)
     def to_screen(self, s):
         print(s)
     def trouble(self, s, tb=None):
@@ -96,6 +98,14 @@ class TestYoutubeSubtitles(unittest.TestCase):
         IE = YoutubeIE(DL)
         info_dict = IE.extract('QRS8MkLhQmM')
         self.assertEqual(info_dict, None)
+    def test_youtube_automatic_captions(self):
+        DL = FakeDownloader()
+        DL.params['writesubtitles'] = True
+        DL.params['subtitleslang'] = 'it'
+        IE = YoutubeIE(DL)
+        info_dict = IE.extract('8YoUxe5ncPo')
+        sub = info_dict[0]['subtitles'][0]
+        self.assertTrue(sub[2] is not None)
 
 if __name__ == '__main__':
     unittest.main()

youtube_dl/InfoExtractors.py

@@ -376,6 +376,34 @@ class YoutubeIE(InfoExtractor):
             return (u'Did not fetch video subtitles', None, None)
         return (None, sub_lang, sub)
 
+    def _request_automatic_caption(self, video_id, webpage):
+        """We need the webpage for getting the captions url, pass it as an
+           argument to speed up the process."""
+        sub_lang = self._downloader.params.get('subtitleslang')
+        sub_format = self._downloader.params.get('subtitlesformat')
+        self.to_screen(u'%s: Looking for automatic captions' % video_id)
+        mobj = re.search(r';ytplayer.config = ({.*?});', webpage)
+        err_msg = u'Couldn\'t find automatic captions for "%s"' % sub_lang
+        if mobj is None:
+            return [(err_msg, None, None)]
+        player_config = json.loads(mobj.group(1))
+        try:
+            args = player_config[u'args']
+            caption_url = args[u'ttsurl']
+            timestamp = args[u'timestamp']
+            params = compat_urllib_parse.urlencode({
+                'lang': 'en',
+                'tlang': sub_lang,
+                'fmt': sub_format,
+                'ts': timestamp,
+                'kind': 'asr',
+            })
+            subtitles_url = caption_url + '&' + params
+            sub = self._download_webpage(subtitles_url, video_id, u'Downloading automatic captions')
+            return [(None, sub_lang, sub)]
+        except KeyError:
+            return [(err_msg, None, None)]
+
     def _extract_subtitle(self, video_id):
         """
         Return a list with a tuple:
@@ -623,7 +651,14 @@ class YoutubeIE(InfoExtractor):
             if video_subtitles:
                 (sub_error, sub_lang, sub) = video_subtitles[0]
                 if sub_error:
-                    self._downloader.report_error(sub_error)
+                    # We try with the automatic captions
+                    video_subtitles = self._request_automatic_caption(video_id, video_webpage)
+                    (sub_error_auto, sub_lang, sub) = video_subtitles[0]
+                    if sub is not None:
+                        pass
+                    else:
+                        # We report the original error
+                        self._downloader.report_error(sub_error)
 
         if self._downloader.params.get('allsubtitles', False):
             video_subtitles = self._extract_all_subtitles(video_id)