theora_encode: 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_encode - from package: theora-tools

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

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