mp2enc: 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/mp2enc - from package: mjpegtools

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

Error in other languages:
mp2enc: bevel nie gevind nie
mp2enc: comandă negăsită
mp2enc: comando não encontrado
mp2enc: commande introuvable
mp2enc: command not found
mp2enc: käsku ei ole
mp2enc: không tìm thấy lệnh
mp2enc: komanda nerasta
mp2enc: Kommando nicht gefunden.
mp2enc: kommandot finns inte
mp2enc: komut yok
mp2enc: nie znaleziono polecenia
mp2enc: níor aimsíodh an t-ordú
mp2enc: no se encontró la orden
mp2enc: no s'ha trobat l'ordre
mp2enc: opdracht niet gevonden
mp2enc: parancs nem található
mp2enc: perintah tidak ditemukan
mp2enc: príkaz nenájdený
mp2enc: příkaz nenalezen
mp2enc: команда не найдена
mp2enc: командата не е открита
mp2enc: 命令找不到
mp2enc: コマンドが見つかりません