This is the code:
try:
s = check_output(['mediainfo', '--Inform=General;%Format%', filename]) # Gets the output from mediainfo
When running it, I get
subprocess.CalledProcessError: Command '['mediainfo', '--Inform=General;%Format%', 'xyz']' returned non-zero exit status 1
When running mediainfo --Inform='Video;%Format%' s03e07.mkv
in a terminal, I get the desired output though, so what's going on here?