lavplay: 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/lavplay - from package: mjpegtools

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

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