mpeg3cat: 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/mpeg3cat - from package: mpeg3-utils

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

Error in other languages:
mpeg3cat: bevel nie gevind nie
mpeg3cat: comandă negăsită
mpeg3cat: comando não encontrado
mpeg3cat: commande introuvable
mpeg3cat: command not found
mpeg3cat: käsku ei ole
mpeg3cat: không tìm thấy lệnh
mpeg3cat: komanda nerasta
mpeg3cat: Kommando nicht gefunden.
mpeg3cat: kommandot finns inte
mpeg3cat: komut yok
mpeg3cat: nie znaleziono polecenia
mpeg3cat: níor aimsíodh an t-ordú
mpeg3cat: no se encontró la orden
mpeg3cat: no s'ha trobat l'ordre
mpeg3cat: opdracht niet gevonden
mpeg3cat: parancs nem található
mpeg3cat: perintah tidak ditemukan
mpeg3cat: príkaz nenájdený
mpeg3cat: příkaz nenalezen
mpeg3cat: команда не найдена
mpeg3cat: командата не е открита
mpeg3cat: 命令找不到
mpeg3cat: コマンドが見つかりません