[SovietsCloset] Add duration from m3u8 (#908)

Authored by: ChillingPepper

yt_dlp/extractor/common.py

@@ -2219,6 +2219,25 @@ class InfoExtractor(object):
                 last_stream_inf = {}
         return formats, subtitles
 
+    def _extract_m3u8_vod_duration(
+            self, m3u8_vod_url, video_id, note=None, errnote=None, data=None, headers={}, query={}):
+
+        m3u8_vod = self._download_webpage(
+            m3u8_vod_url, video_id,
+            note='Downloading m3u8 VOD manifest' if note is None else note,
+            errnote='Failed to download VOD manifest' if errnote is None else errnote,
+            fatal=False, data=data, headers=headers, query=query)
+
+        return self._parse_m3u8_vod_duration(m3u8_vod or '', video_id)
+
+    def _parse_m3u8_vod_duration(self, m3u8_vod, video_id):
+        if '#EXT-X-PLAYLIST-TYPE:VOD' not in m3u8_vod:
+            return None
+
+        return int(sum(
+            float(line[len('#EXTINF:'):].split(',')[0])
+            for line in m3u8_vod.splitlines() if line.startswith('#EXTINF:'))) or None
+
     @staticmethod
     def _xpath_ns(path, namespace=None):
         if not namespace: