There are several parts of the camera synchronization task.
- Camera should receive synchronizing event. It can be done by either special hardware inputs or just over the network. It most cases if you want to syncronize 2 or more networked cameras you do not need extra wires, so the network sycnchronizatrion is the most convinient. But sometimes you would like to be able to trigger the camera without the network - i.e. from some contact closure.
- Camera should be able to start image acquisition process when required - generally not possible with most CMOS sensors. /this used with "external trigger" in FPGA API? - Spectr/
- And (in some cases) camera should be able to precisely keep time, so in-sync state of two or more cameras will last longer.