x264: 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 Debian possible default full paths are:

/usr/bin/x264 - from package: x264

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

Error in other languages:
x264: bevel nie gevind nie
x264: comandă negăsită
x264: comando não encontrado
x264: commande introuvable
x264: command not found
x264: käsku ei ole
x264: không tìm thấy lệnh
x264: komanda nerasta
x264: Kommando nicht gefunden.
x264: kommandot finns inte
x264: komut yok
x264: nie znaleziono polecenia
x264: níor aimsíodh an t-ordú
x264: no se encontró la orden
x264: no s'ha trobat l'ordre
x264: opdracht niet gevonden
x264: parancs nem található
x264: perintah tidak ditemukan
x264: príkaz nenájdený
x264: příkaz nenalezen
x264: команда не найдена
x264: командата не е открита
x264: 命令找不到
x264: コマンドが見つかりません