.tidx is Thumbnail index
Key Features: .TIDX File Extension
What is an .TIDX file?
The tidx file extension is mainly related to AACS (Advanced Access Content System), a multimedia protection system for Blu-ray Disc. These *.tidx files are used for thumbnail indexes.
Example: menu.tidx, mark.tidx
This tidx file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.