[youtube_live_chat] Fix download with cookies (#437)

Closes #417 

Authored by: siikamiika

yt_dlp/downloader/youtube_live_chat.py

@@ -59,6 +59,17 @@ class YoutubeLiveChatFD(FragmentFD):
             self._append_fragment(ctx, processed_fragment)
             return continuation_id, offset
 
+        def try_refresh_replay_beginning(live_chat_continuation):
+            # choose the second option that contains the unfiltered live chat replay
+            refresh_continuation_id = try_get(
+                live_chat_continuation,
+                lambda x: x['header']['liveChatHeaderRenderer']['viewSelector']['sortFilterSubMenuRenderer']['subMenuItems'][1]['continuation']['reloadContinuationData']['continuation'], str)
+            if refresh_continuation_id:
+                # no data yet but required to call _append_fragment
+                self._append_fragment(ctx, b'')
+                return refresh_continuation_id, 0
+            return parse_actions_replay(live_chat_continuation)
+
         live_offset = 0
 
         def parse_actions_live(live_chat_continuation):
@@ -90,23 +101,29 @@ class YoutubeLiveChatFD(FragmentFD):
             self._append_fragment(ctx, processed_fragment)
             return continuation_id, live_offset
 
-        if info_dict['protocol'] == 'youtube_live_chat_replay':
-            parse_actions = parse_actions_replay
-        elif info_dict['protocol'] == 'youtube_live_chat':
-            parse_actions = parse_actions_live
-
-        def download_and_parse_fragment(url, frag_index, request_data, headers):
+        def download_and_parse_fragment(url, frag_index, request_data=None, headers=None):
             count = 0
             while count <= fragment_retries:
                 try:
                     success, raw_fragment = dl_fragment(url, request_data, headers)
                     if not success:
                         return False, None, None
+                    try:
+                        data = ie._extract_yt_initial_data(video_id, raw_fragment.decode('utf-8', 'replace'))
+                    except RegexNotFoundError:
+                        data = None
+                    if not data:
                         data = json.loads(raw_fragment)
                     live_chat_continuation = try_get(
                         data,
                         lambda x: x['continuationContents']['liveChatContinuation'], dict) or {}
-                    continuation_id, offset = parse_actions(live_chat_continuation)
+                    if info_dict['protocol'] == 'youtube_live_chat_replay':
+                        if frag_index == 1:
+                            continuation_id, offset = try_refresh_replay_beginning(live_chat_continuation)
+                        else:
+                            continuation_id, offset = parse_actions_replay(live_chat_continuation)
+                    elif info_dict['protocol'] == 'youtube_live_chat':
+                        continuation_id, offset = parse_actions_live(live_chat_continuation)
                     return True, continuation_id, offset
                 except compat_urllib_error.HTTPError as err:
                     count += 1
@@ -142,8 +159,10 @@ class YoutubeLiveChatFD(FragmentFD):
         visitor_data = try_get(innertube_context, lambda x: x['client']['visitorData'], str)
         if info_dict['protocol'] == 'youtube_live_chat_replay':
             url = 'https://www.youtube.com/youtubei/v1/live_chat/get_live_chat_replay?key=' + api_key
+            chat_page_url = 'https://www.youtube.com/live_chat_replay?continuation=' + continuation_id
         elif info_dict['protocol'] == 'youtube_live_chat':
             url = 'https://www.youtube.com/youtubei/v1/live_chat/get_live_chat?key=' + api_key
+            chat_page_url = 'https://www.youtube.com/live_chat?continuation=' + continuation_id
 
         frag_index = offset = 0
         while continuation_id is not None:
@@ -159,6 +178,8 @@ class YoutubeLiveChatFD(FragmentFD):
                 fragment_request_data = json.dumps(request_data, ensure_ascii=False).encode('utf-8') + b'\n'
                 success, continuation_id, offset = download_and_parse_fragment(
                     url, frag_index, fragment_request_data, headers)
+            else:
+                success, continuation_id, offset = download_and_parse_fragment(chat_page_url, frag_index)
             if not success:
                 return False
             if test: