Currently --Output=JSON outputs a json object if passed a single file and an array of json objects if passed 2+ files:

$ mediainfo --Output=JSON 1.mkv
{ ... }
$ mediainfo --Output=JSON 1.mkv 2.mkv
[ { ... }, { ... } ] 

This creates a problem in scripts that deal with arbitrary number of files (sometimes 1, sometimes 2+) as an object and an array of objects need to be handled differently.

Suggestion: always output an array of objects (in case of 1 file - an array with a single object).