I am remuxing a series of German TV shows from .avi to mkv, including subtitles. The subs are in the form of an .idx file and a .sub file. Episodes 1-11 have all worked without any issues, but episode 12 is giving me the message “The file xyz.idx’ was not recognized as a supported format (exit code: 2).” I have searched for this problem, and the answers I found referred to missing language codes. I have compared the language codes in the idx files that worked, with the one that isn’t working, and I can’t see any difference. Can anyone help me with this?
I am using MkvToolnix v82.0 and Windows 10.
EDIT: After making this post it occurred to me that the files I was remuxing had names which were much longer than I would ever use myself. I wondered if this could be causing problems. I shortened all the file names and now it is working. Is the length of filenames an known issue with MkvToolNix?