ebml_validator: 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/ebml_validator - from package: mkvtoolnix

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

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