mediainfo-qt: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/mediainfo-qt - from package: mediainfo-qt

You may install the required package with command yum install {package}

Error in other languages:
mediainfo-qt: bevel nie gevind nie
mediainfo-qt: comandă negăsită
mediainfo-qt: comando não encontrado
mediainfo-qt: commande introuvable
mediainfo-qt: command not found
mediainfo-qt: käsku ei ole
mediainfo-qt: không tìm thấy lệnh
mediainfo-qt: komanda nerasta
mediainfo-qt: Kommando nicht gefunden.
mediainfo-qt: kommandot finns inte
mediainfo-qt: komut yok
mediainfo-qt: nie znaleziono polecenia
mediainfo-qt: níor aimsíodh an t-ordú
mediainfo-qt: no se encontró la orden
mediainfo-qt: no s'ha trobat l'ordre
mediainfo-qt: opdracht niet gevonden
mediainfo-qt: parancs nem található
mediainfo-qt: perintah tidak ditemukan
mediainfo-qt: príkaz nenájdený
mediainfo-qt: příkaz nenalezen
mediainfo-qt: команда не найдена
mediainfo-qt: командата не е открита
mediainfo-qt: 命令找不到
mediainfo-qt: コマンドが見つかりません