png2theora: command not found

Have You tried accessing the binary with the full path?

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/png2theora - from package: theora-tools

You may install the required package with command yum install {package}
Error in other languages:
png2theora: bevel nie gevind nie
png2theora: comandă negăsită
png2theora: comando não encontrado
png2theora: commande introuvable
png2theora: command not found
png2theora: käsku ei ole
png2theora: không tìm thấy lệnh
png2theora: komanda nerasta
png2theora: Kommando nicht gefunden.
png2theora: kommandot finns inte
png2theora: komut yok
png2theora: nie znaleziono polecenia
png2theora: níor aimsíodh an t-ordú
png2theora: no se encontró la orden
png2theora: no s'ha trobat l'ordre
png2theora: opdracht niet gevonden
png2theora: parancs nem található
png2theora: perintah tidak ditemukan
png2theora: príkaz nenájdený
png2theora: příkaz nenalezen
png2theora: команда не найдена
png2theora: командата не е открита
png2theora: 命令找不到
png2theora: コマンドが見つかりません