[youtube:tab] Extract more playlist metadata (#2069)

* Add fields modified_date, modified_timestamp
* Add field playlist_count
* [youtube:tab] Extract view_count, playlist_count, modified_date

Authored by: coletdjnz, pukkandan

1 files changed, 13 insertions, 3 deletions

diff --git a/yt_dlp/extractor/common.py b/yt_dlp/extractor/common.py
index 79f53c9c2..7c83991ea 100644
--- a/yt_dlp/extractor/common.py
+++ b/yt_dlp/extractor/common.py
@@ -243,11 +243,16 @@ class InfoExtractor(object):
     uploader:       Full name of the video uploader.
     license:        License name the video is licensed under.
     creator:        The creator of the video.
-    release_timestamp: UNIX timestamp of the moment the video was released.
-    release_date:   The date (YYYYMMDD) when the video was released.
     timestamp:      UNIX timestamp of the moment the video was uploaded
     upload_date:    Video upload date (YYYYMMDD).
-                    If not explicitly set, calculated from timestamp.
+                    If not explicitly set, calculated from timestamp
+    release_timestamp: UNIX timestamp of the moment the video was released.
+                    If it is not clear whether to use timestamp or this, use the former
+    release_date:   The date (YYYYMMDD) when the video was released.
+                    If not explicitly set, calculated from release_timestamp
+    modified_timestamp: UNIX timestamp of the moment the video was last modified.
+    modified_date:   The date (YYYYMMDD) when the video was last modified.
+                    If not explicitly set, calculated from modified_timestamp
     uploader_id:    Nickname or id of the video uploader.
     uploader_url:   Full URL to a personal webpage of the video uploader.
     channel:        Full name of the channel the video is uploaded on.
@@ -383,6 +388,11 @@ class InfoExtractor(object):
     Additionally, playlists can have "id", "title", and any other relevent
     attributes with the same semantics as videos (see above).
 
+    It can also have the following optional fields:
+
+    playlist_count: The total number of videos in a playlist. If not given,
+                    YoutubeDL tries to calculate it from "entries"
+
 
     _type "multi_video" indicates that there are multiple videos that
     form a single show, for examples multiple acts of an opera or TV episode.