xvidtune: 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/xvidtune - from package: xorg-x11-apps

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

On Debian possible default full paths are:

/usr/bin/xvidtune - from package: x11-xserver-utils

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

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