pelco via arduinio

Hi everyone, I apologize in advance for my English.
Help ..
I have an ip camera that supports zoom via the Pelco P and Pelco D. Protocols I would like to use the Arduinio to control the camera zoom via rs 232 3.3v (possibly in the future full PTZ)

I have a cheap camera from china (http://www.hankvision.com/chanpin/yitijixin/501.html) theoretically it supports onvif but I can not run it with any program.
description of camera connectors HD-8218G PIN definition
I know that there are projects on the net, but I am quite a novice utility and I need to do it because every now and then destroy my car and I need to record bandits.
greetings
Voyteck