dc1394_vloopback: 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/dc1394_vloopback - from package: libdc1394-tools

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

Error in other languages:
dc1394_vloopback: bevel nie gevind nie
dc1394_vloopback: comandă negăsită
dc1394_vloopback: comando não encontrado
dc1394_vloopback: commande introuvable
dc1394_vloopback: command not found
dc1394_vloopback: käsku ei ole
dc1394_vloopback: không tìm thấy lệnh
dc1394_vloopback: komanda nerasta
dc1394_vloopback: Kommando nicht gefunden.
dc1394_vloopback: kommandot finns inte
dc1394_vloopback: komut yok
dc1394_vloopback: nie znaleziono polecenia
dc1394_vloopback: níor aimsíodh an t-ordú
dc1394_vloopback: no se encontró la orden
dc1394_vloopback: no s'ha trobat l'ordre
dc1394_vloopback: opdracht niet gevonden
dc1394_vloopback: parancs nem található
dc1394_vloopback: perintah tidak ditemukan
dc1394_vloopback: príkaz nenájdený
dc1394_vloopback: příkaz nenalezen
dc1394_vloopback: команда не найдена
dc1394_vloopback: командата не е открита
dc1394_vloopback: 命令找不到
dc1394_vloopback: コマンドが見つかりません