dirac_RGBtoYUV420: 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/dirac_RGBtoYUV420 - from package: dirac

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

Error in other languages:
dirac_RGBtoYUV420: bevel nie gevind nie
dirac_RGBtoYUV420: comandă negăsită
dirac_RGBtoYUV420: comando não encontrado
dirac_RGBtoYUV420: commande introuvable
dirac_RGBtoYUV420: command not found
dirac_RGBtoYUV420: käsku ei ole
dirac_RGBtoYUV420: không tìm thấy lệnh
dirac_RGBtoYUV420: komanda nerasta
dirac_RGBtoYUV420: Kommando nicht gefunden.
dirac_RGBtoYUV420: kommandot finns inte
dirac_RGBtoYUV420: komut yok
dirac_RGBtoYUV420: nie znaleziono polecenia
dirac_RGBtoYUV420: níor aimsíodh an t-ordú
dirac_RGBtoYUV420: no se encontró la orden
dirac_RGBtoYUV420: no s'ha trobat l'ordre
dirac_RGBtoYUV420: opdracht niet gevonden
dirac_RGBtoYUV420: parancs nem található
dirac_RGBtoYUV420: perintah tidak ditemukan
dirac_RGBtoYUV420: príkaz nenájdený
dirac_RGBtoYUV420: příkaz nenalezen
dirac_RGBtoYUV420: команда не найдена
dirac_RGBtoYUV420: командата не е открита
dirac_RGBtoYUV420: 命令找不到
dirac_RGBtoYUV420: コマンドが見つかりません