Fix Twitch VOD timestamps being offset by ~60 seconds

Author: Mikachu

demux/demux_timeline.c

@@ -250,6 +250,8 @@ static void switch_segment(struct demuxer *demuxer, struct virtual_source *src,
     reselect_streams(demuxer);
     if (!src->no_clip)
         demux_set_ts_offset(new->d, new->start - new->d_start);
+    else if (src->delay_open)
+        demux_set_ts_offset(new->d, new->start - new->d->start_time);
     if (!src->no_clip || !init)
         demux_seek(new->d, start_pts, flags);