Yes, I have you thoroughly misunderstood.
You have wrote:
"so i right click on the video file in the playlist ... updated the playlist title info by selecting the information tag ... i click save after the updated ... but it seems it can not save the updated title info to the video file ... because i see the same title info after i reopen the video file...
i like to ask how i can save the updated title info into the video file?"
"Title" is for me the name of a video object, for example, "Bartoli in Italy" and not the name of the video file.
The name of a video file may be, for example, "Bartoli.mp4".
But you have with "title" the column heading "Title" in the playlist meant.
The VLC checks for the entry in the "Title" column, whether he finds a title information for the object.
A title information can be in the object file, typical for the tags in the MP3 files, or in the playlist.
For videos can record such information only a few formats.
If no title information was found, the VLC wearing the file name.
You have title information for your video files written, which must now be removed:
- You make a right click on the video file in the playlist,
- updated the playlist title info by selecting for "Title" to nothing (""),
- click save after the updated,
- save a new playlist.
greeting