I'm using 4 single camera USB capture devices with zoneminder. They are K-World USB2800D, about $25 each from NewEgg.
Work very well. They have composite and S-Video. I tried using them as dual cameras switching inputs but the overhead of switching barely allowed 3 fps. When using composite and S-Video on a BT8x8 PCI card for two cameras it works a lot better usually ~12 fps.
For my purposes 5 fps or above is fine.
Cheap is good, but at some point its cheaper to just buy something that works.
I am using also using these with gstreamer for a real time image processing application and on some computers there are USB issues where only one will work unless the other is plugged into a non motherboard USB port -- showstopper when using a notebook without PCMCIA. But my computer at home running ZM does not have this issue at all, not sure what is going on here.
Sensoray makes a nice four channel USB capture box (USB powered!) that installs as four /dev/video once you compile their driver, but it costs about $500
Got one for the above notebook system at work, they'd be great for ZM is the price was lower. Its model 2255S.
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