What software for an IP video surveillance system for 50 cameras should I choose?

Question

CCTV

the task is to build a video surveillance system for 50 cameras with a possible expansion further.
There is already a system for 40 Axis cameras - a server on CentOS writes to the archive on motion using motion, security watches cameras using the zoneminder client. The existing disadvantages are high load on the server and low recording resolution, motion does not want to write more than 640x480 to any and does not understand rtsp. Migration to a more convenient solution is planned.
Tell me the software for the server:
- understands rtsp
- writes an archive based on the movement in the frame
- supports a resolution of 800x600 and higher
- a client for the security post
- preferably free, in extreme cases inexpensive
You can even have separate software for recording and software for viewing real-time streams.

Answer 1

We use the Line program, with almost no complaints
www.devline.ru/ip-videonabljudenie/line_ip.html

Answer 2

Of the good - probably Milestone. Or a separate piece of hardware like Synology. Will work with a bang.
Alternatively, you can use the software from Axis itself.

Answer 3

ZoneMinder
https://zoneminder.com/ Bluecherry https://www.bluecherrydvr.com/ https://github.com/bluecherrydvr