[youtube] Improve stretch extraction and fix stretched ratio calculation (closes #28769)

youtube_dl/extractor/youtube.py

@@ -812,6 +812,11 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
             },
             'skip': 'This video does not exist.',
         },
+        {
+            # Video with incomplete 'yt:stretch=16:'
+            'url': 'https://www.youtube.com/watch?v=FRhJzUSJbGI',
+            'only_matching': True,
+        },
         {
             # Video licensed under Creative Commons
             'url': 'https://www.youtube.com/watch?v=M4gD1WSo5mA',
@@ -1717,13 +1722,16 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 for m in re.finditer(self._meta_regex('og:video:tag'), webpage)]
         for keyword in keywords:
             if keyword.startswith('yt:stretch='):
-                w, h = keyword.split('=')[1].split(':')
+                mobj = re.search(r'(\d+)\s*:\s*(\d+)', keyword)
-                w, h = int(w), int(h)
+                if mobj:
+                    # NB: float is intentional for forcing float division
+                    w, h = (float(v) for v in mobj.groups())
                     if w > 0 and h > 0:
                         ratio = w / h
                         for f in formats:
                             if f.get('vcodec') != 'none':
                                 f['stretched_ratio'] = ratio
+                        break
 
         thumbnails = []
         for container in (video_details, microformat):