Just finished setting up Hikvision monitoring today, via Hikvision API. It is much more reliable and actually offers some valid data.
Cameras: http://down.dipol.com.pl/Cctv/-Hikvision-/isapi/HIKVISION%20ISAPI_2.6-IPMD%20Service.pdf
NVRs: http://down.dipol.com.pl/Cctv/-Hikvision-/isapi/HIKVISION%20ISAPI_2.0-RaCM%20Service.pdf
No easy way of integrating with LibreNMS, though.