theora_player: 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/theora_player - from package: theora-tools

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

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