[youtube] Extract formats from multiple DASH manifests (Closes #6093)

DASH manifest pointed by dashmpd from the video webpage and one pointed by get_video_info may
be different (namely different itag set) - some itags are missing from DASH manifest pointed by
webpage's dashmpd, some - from DASH manifest pointed by get_video_info's dashmpd).
The general idea is to take a union of itags of both DASH manifests (for example video with such
'manifest behavior' see https://github.com/rg3/youtube-dl/issues/6093).

youtube_dl/extractor/youtube.py

@@ -853,6 +853,13 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         else:
             player_url = None
 
+        dash_mpds = []
+
+        def add_dash_mpd(video_info):
+            dash_mpd = video_info.get('dashmpd')
+            if dash_mpd and dash_mpd[0] not in dash_mpds:
+                dash_mpds.append(dash_mpd[0])
+
         # Get video info
         embed_webpage = None
         if re.search(r'player-age-gate-content">', video_webpage) is not None:
@@ -873,34 +880,40 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 note='Refetching age-gated info webpage',
                 errnote='unable to download video info webpage')
             video_info = compat_parse_qs(video_info_webpage)
+            add_dash_mpd(video_info)
         else:
             age_gate = False
-            try:
-                # Try looking directly into the video webpage
-                mobj = re.search(r';ytplayer\.config\s*=\s*({.*?});', video_webpage)
-                if not mobj:
-                    raise ValueError('Could not find ytplayer.config')  # caught below
+            # Try looking directly into the video webpage
+            mobj = re.search(r';ytplayer\.config\s*=\s*({.*?});', video_webpage)
+            if mobj:
                 json_code = uppercase_escape(mobj.group(1))
                 ytplayer_config = json.loads(json_code)
                 args = ytplayer_config['args']
-                # Convert to the same format returned by compat_parse_qs
-                video_info = dict((k, [v]) for k, v in args.items())
-                if not args.get('url_encoded_fmt_stream_map'):
-                    raise ValueError('No stream_map present')  # caught below
-            except ValueError:
-                # We fallback to the get_video_info pages (used by the embed page)
-                self.report_video_info_webpage_download(video_id)
-                for el_type in ['&el=embedded', '&el=detailpage', '&el=vevo', '']:
-                    video_info_url = (
-                        '%s://www.youtube.com/get_video_info?&video_id=%s%s&ps=default&eurl=&gl=US&hl=en'
-                        % (proto, video_id, el_type))
-                    video_info_webpage = self._download_webpage(
-                        video_info_url,
-                        video_id, note=False,
-                        errnote='unable to download video info webpage')
-                    video_info = compat_parse_qs(video_info_webpage)
-                    if 'token' in video_info:
-                        break
+                if args.get('url_encoded_fmt_stream_map'):
+                    # Convert to the same format returned by compat_parse_qs
+                    video_info = dict((k, [v]) for k, v in args.items())
+                    add_dash_mpd(video_info)
+            # We also try looking in get_video_info since it may contain different dashmpd
+            # URL that points to a DASH manifest with possibly different itag set (some itags
+            # are missing from DASH manifest pointed by webpage's dashmpd, some - from DASH
+            # manifest pointed by get_video_info's dashmpd).
+            # The general idea is to take a union of itags of both DASH manifests (for example
+            # video with such 'manifest behavior' see https://github.com/rg3/youtube-dl/issues/6093)
+            self.report_video_info_webpage_download(video_id)
+            for el_type in ['&el=info', '&el=embedded', '&el=detailpage', '&el=vevo', '']:
+                video_info_url = (
+                    '%s://www.youtube.com/get_video_info?&video_id=%s%s&ps=default&eurl=&gl=US&hl=en'
+                    % (proto, video_id, el_type))
+                video_info_webpage = self._download_webpage(
+                    video_info_url,
+                    video_id, note=False,
+                    errnote='unable to download video info webpage')
+                get_video_info = compat_parse_qs(video_info_webpage)
+                add_dash_mpd(get_video_info)
+                if not video_info:
+                    video_info = get_video_info
+                if 'token' in get_video_info:
+                    break
         if 'token' not in video_info:
             if 'reason' in video_info:
                 raise ExtractorError(
@@ -1118,24 +1131,26 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
 
         # Look for the DASH manifest
         if self._downloader.params.get('youtube_include_dash_manifest', True):
-            dash_mpd = video_info.get('dashmpd')
-            if dash_mpd:
-                dash_manifest_url = dash_mpd[0]
+            for dash_manifest_url in dash_mpds:
+                dash_formats = {}
                 try:
-                    dash_formats = self._parse_dash_manifest(
-                        video_id, dash_manifest_url, player_url, age_gate)
+                    for df in self._parse_dash_manifest(
+                            video_id, dash_manifest_url, player_url, age_gate):
+                        # Do not overwrite DASH format found in some previous DASH manifest
+                        if df['format_id'] not in dash_formats:
+                            dash_formats[df['format_id']] = df
                 except (ExtractorError, KeyError) as e:
                     self.report_warning(
                         'Skipping DASH manifest: %r' % e, video_id)
-                else:
+                if dash_formats:
                     # Remove the formats we found through non-DASH, they
                     # contain less info and it can be wrong, because we use
                     # fixed values (for example the resolution). See
                     # https://github.com/rg3/youtube-dl/issues/5774 for an
                     # example.
-                    dash_keys = set(df['format_id'] for df in dash_formats)
+                    dash_keys = set(df['format_id'] for df in dash_formats.values())
                     formats = [f for f in formats if f['format_id'] not in dash_keys]
-                    formats.extend(dash_formats)
+                    formats.extend(dash_formats.values())
 
         # Check for malformed aspect ratio
         stretched_m = re.search(