mediainfo: 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 - from package: mediainfo

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

On Debian possible default full paths are:

/usr/bin/mediainfo - from package: mediainfo

You may install the required package with command apt-get install {package}

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