How can I remove custom thumbnail from mkv files?

[Gerff]

I'm new around here and I didn't know where to fit this thread. Anyway, I have just donwloaded a mkv file and it came with a custom thumbnail on it, which annoys me because I like to keep my TV shows folders organized. I would like to know if there's a way I can remove that thumbnail or make the default one appear instead.

[poisondeathray]

If it's just cover art, you can use mkvtoolnix (mkvmerge) to remove the attachment, remux a new mkv. If it's actually encoded in the file as an intro you can split the file (mkvtoolnix as well)

[Gerff]

Does it change the quality of the video?

[poisondeathray]

Remuxing doesn't change the quality of the video . It's like taking the audio & video out of box and putting it into another box

[Gerff]

Oh, nice. Well, thanks. It worked!

[Viper3773]

In case anyone else finds this from Google search like myself, after installing mkvtoolnix (mkvmerge), you can run this simple script to remove attachments.

https://virginsecurity.wordpress.com/2016/01/26/bulck-remove-art-cover-from-mkv-files/

@ECHO OFF
SET MKVPROEDIT="C:\mkvtoolnix-64bit-8.8.0\"
SET /P PATH="Enter folder path: "
IF EXIST %PATH:~1,-1%
(
   FOR /F "tokens=*" %%i IN ('dir /B /S %PATH%"\*.mkv"') DO (
       ECHO [+] Processing File: "%%i"
       START /D %MKVPROEDIT% /B /W mkvpropedit.exe "%%i" --delete-attachment mime-type:image/jpeg
       ECHO.
   )
)
SET /P X="Press any key to continue.."
@ECHO ON

Paste into notepad and save as a .bat file. You can then double click the .bat file and enter your folder path to remove attachments.

Note: I had to change line 2 with the path of where mkvoolnix was installed; in my case: C:\Program Files\MKVToolNix