oggdec: 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 CentOS possible default full paths are:

/usr/bin/oggdec - from package: vorbis-tools

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/oggdec - from package: vorbis-tools

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

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