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 Debian possible default full paths are:

/usr/bin/RGBtoYUV420 - from package: dirac

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

Error in other languages:
RGBtoYUV420: bevel nie gevind nie
RGBtoYUV420: comandă negăsită
RGBtoYUV420: comando não encontrado
RGBtoYUV420: commande introuvable
RGBtoYUV420: command not found
RGBtoYUV420: käsku ei ole
RGBtoYUV420: không tìm thấy lệnh
RGBtoYUV420: komanda nerasta
RGBtoYUV420: Kommando nicht gefunden.
RGBtoYUV420: kommandot finns inte
RGBtoYUV420: komut yok
RGBtoYUV420: nie znaleziono polecenia
RGBtoYUV420: níor aimsíodh an t-ordú
RGBtoYUV420: no se encontró la orden
RGBtoYUV420: no s'ha trobat l'ordre
RGBtoYUV420: opdracht niet gevonden
RGBtoYUV420: parancs nem található
RGBtoYUV420: perintah tidak ditemukan
RGBtoYUV420: príkaz nenájdený
RGBtoYUV420: příkaz nenalezen
RGBtoYUV420: команда не найдена
RGBtoYUV420: командата не е открита
RGBtoYUV420: 命令找不到
RGBtoYUV420: コマンドが見つかりません