What version of BI are you using? A user told me that BI5 supports ONVIF. You could try it, but you need to upgrade to hikvision's fw. Try it before upgrading the repeater. As you can see, bandwidth requirements for the camera, even at full frame and resolution is low, so if the signal is ok it should not be a problem. If you have s ynology you don't have costs: SSS on NAS has 2 device license included, so you can use it for the doorbell. Even with Synology, I highly recommend ONVIF interface, but it works in RTSP too, with less functionalities, less integration.