qt-faststart: command not found

Have You tried accessing the binary with the full path?

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/qt-faststart - from package: libav-tools

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