The GUI states "JSON output generated by mkvmerge could not be parsed"
Adding a file in the GUI popups up an error message similar to the following ones:
Error executing mkvmerge The JSON output generated by mkvmerge could not be parsed (parser's error message: parse error - unexpected `[`; expected end of input).
Error executing mkvmerge The JSON output generated by mkvmerge could not be parsed (parser's error message: parse error - unexpected `m`).
Possible solution 1: blocked by Anti Virus programs
Several users have reported such a case, and in each case it was due to their Anti Virus program blocking or interfering with
Please configure your Anti Virus solution to exempt
mkvmerge.exe from scanning. It's located in the MKVToolNix installation folder. Then delete the MKVToolNix cache directory (make sure MKVToolNix GUI isn't running). Last start the GUI and try the operation again.
Possible solution 2: versions of mkvmerge the GUI differ
MKVToolNix GUI and mkvmerge must always be the same version. You cannot run the e.g. GUI v9.7.1 with mkvmerge v9.4.2. Verify that the
mkvtoolnix-gui executables located in the same folder have the same version number.
On Windows that version number can be found in the files' properties:
On all operating systems you can compare the version numbers output by both programs. Here's an example for Linux:
/usr/bin/mkvmerge --version /usr/bin/mkvtoolnix-gui --version
Possible solution 3: the cache is corrupted
Before deleting the cache folder, first make sure MKVToolNix GUI isn't running anymore. Then locate the cache folder and simply delete it. Then try adding the file(s) again.