The GXV3504 is a grandstream 4 port video encoder. It takes an analog stream and encodes it to ip video accessible on the LAN through tcp/ip ethernet.
path is: /snapshot/view0.jpg
there are four channels view0, view1, view2, and view3 respectively.
Resolution is 704x480px (seems to be standard for analog camera encoders)
It works in Zoneminder at about 2fps. Less if you use >2 cameras.
I have a number of these used, and they have done poorly. Hardware has failed over time. I recommend finding a different video encoder, unless you get this free. Use with caution.
They have a telnet interface where you can reboot, and change settings.
Try a better name brand.