Let us see how we can fix this issue.

This Blu-ray Disc needs a library for AACS decoding

There are two scenarios that can trigger this error. They are-

Blu-ray disks are being protected by AACS and BD+ technologies.The KeyFB.cfg file is missing.

The fix for both of them requires the same steps to be undertaken. First of all, you need to check the architecture of Windows and VLC is installed on your computer. It will be helpful. Now, visit this third-party website here. You need to get the Keys Database (KEYDb.cfg) file which is the same, irrespective of your System and VLC architecture. The other file that you need is the AACS Dynamic Library (libaacs.dll) file. This depends on the architecture of VLC Media Player that you have installed. Now, you need to copy the first Keys Database file that you downloaded to the AppData Folder. For that, hit the WINKEY + R button combination on your keyboard. Now, type in %APPDATA%\ and hit Enter. Create a folder in the location opened in the File Explorer and name it as aacs.

Paste the KEYDB.cfg file inside this folder. Now, get the AACS Dynamic File that you downloaded. If you are using an x86 version of VLC Media Player on an x64 version of Windows, just navigate to the following location, C:\Program Files (x86)\VideoLAN\VLC

If you are using an x64 version of VLC Media Player on an x64 version of Windows, or x86 version of VLC Media Player on an x86 version of Windows, just navigate to the following location, Finally, paste the Dynamic Library file libaacs.dll into this location. Open VLC Media Player now and click if the error has been fixed. Note: The link to download the given files above throws an error saying the SSL Certificate for the website is invalid. You can ignore it for this website only as no malicious activities were reported in regards to it.