I use ZoneMinder for various reasons, but mostly because it’s free and from my point of view the only free open source system for video surveillance which is worth your time and money if you donate.
I would like to share with you my experience.How I got a significant low CPU usage from a third party JPEG library, which I use on my CentOS 5 installation with ZoneMinder.This library is well written to optimize the JPEG processing power of the CPU.
I use Intel(R) Xeon(TM) CPU 2.80GHz on DELL PowerEdge 2800. Before using this JPEG library my CPU usage for 6 Y-Cam White cameras was around 90% in MoDetect mode.After installing this libraries I saw a significant decrease on system time with more then 80% less.
The deal is very straight forward just install the JPEG lib from here or here.After that do a full reboot on the machine and check the CPU usage when ZoneMinder runs.If you don’t see an improvement , you might want to try remove any other JPEG libs you have on the node.