RGBtoYUV444: 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/RGBtoYUV444 - from package: dirac

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

Error in other languages:
RGBtoYUV444: bevel nie gevind nie
RGBtoYUV444: comandă negăsită
RGBtoYUV444: comando não encontrado
RGBtoYUV444: commande introuvable
RGBtoYUV444: command not found
RGBtoYUV444: käsku ei ole
RGBtoYUV444: không tìm thấy lệnh
RGBtoYUV444: komanda nerasta
RGBtoYUV444: Kommando nicht gefunden.
RGBtoYUV444: kommandot finns inte
RGBtoYUV444: komut yok
RGBtoYUV444: nie znaleziono polecenia
RGBtoYUV444: níor aimsíodh an t-ordú
RGBtoYUV444: no se encontró la orden
RGBtoYUV444: no s'ha trobat l'ordre
RGBtoYUV444: opdracht niet gevonden
RGBtoYUV444: parancs nem található
RGBtoYUV444: perintah tidak ditemukan
RGBtoYUV444: príkaz nenájdený
RGBtoYUV444: příkaz nenalezen
RGBtoYUV444: команда не найдена
RGBtoYUV444: командата не е открита
RGBtoYUV444: 命令找不到
RGBtoYUV444: コマンドが見つかりません