mediastream: 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

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/mediastream - from package: linphone

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