Combining cameras and recorders from different vendors is common, whether to control cost or to reuse existing equipment, but four things need settling in advance.

• Protocol first: confirm the camera supports ONVIF or standard RTSP, and test streaming and audio during design rather than discovering the gap on site.
• Unified time: point every device at the same NTP source, otherwise timestamps across brands cannot corroborate each other.
• Credential discipline: default accounts differ by brand. Record them at handover and change the defaults, or you create a security hole.
• Power and pinout: verify both sides support the same PoE standard (802.3af or at). Connecting a non-standard PoE device to a standards-compliant switch may deliver no power — or cause damage.
• Feature boundaries: cross-brand analytics, face matching and similar functions generally will not interoperate, so decide during design which features must stay single-vendor.

Document mixed deployments in the as-built pack — brand, model, IP, protocol, account and feature boundaries — and maintenance becomes far quicker later.