gmerlin_psnr: 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/gmerlin_psnr - from package: gmerlin

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

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