If you have ever tried to pull a doorbell camera feed into Frigate, a Synology NVR, or Home Assistant, you have probably discovered that "it has a camera" and "it has a video stream I can use" are two different claims. Here is the gap, and how to plan around it.
Battery doorbells usually have no stream at all
This is the most important thing to know and it is rarely on the box. A battery doorbell spends almost all of its time in a low-power sleep state. It wakes on PIR motion or on a button press, records a short clip, and goes back to sleep.
A continuous RTSP stream is incompatible with that. It requires the Wi-Fi radio and the encoder to be live permanently, which would flatten the battery in hours. So battery doorbells generally offer: event clips through the vendor app, and sometimes a live view on demand through the vendor app while the device happens to be awake.
If your plan is "24/7 recording to my NVR", a battery doorbell is the wrong hardware, not a misconfigured one.
Wired doorbells: RTSP and ONVIF are different things
A mains-powered or transformer-powered Wi-Fi doorbell can keep its radio up, and many of them expose an RTSP URL. ONVIF is a separate, larger standard for discovery and device management — a device can offer RTSP without being ONVIF-compliant, which matters because some NVRs only auto-discover ONVIF devices.
Practically: if your NVR has a "custom RTSP URL" option, you do not need ONVIF. If it only has "search network for cameras", you do.
Expect a main stream and a sub-stream. The main stream is your full-resolution feed; the sub-stream is a lower-resolution feed intended for preview and for motion detection. Use the sub-stream for detection and the main stream only for recording and viewing. This is the single biggest storage and CPU decision you will make.
Do the bandwidth arithmetic before you buy the disk
A 1080p stream at roughly 2 Mbps, recorded continuously, is about 21 GB per day and around 630 GB per month, per camera. A 2K stream can easily be double that.
That is why continuous recording is a wired-camera decision, not a doorbell decision. Most people who think they want 24/7 from a doorbell actually want: a low-resolution always-on preview for occupancy, plus event recordings at full resolution. Size your storage for the second one.
Two-way audio is not in the stream
RTSP carries video and, sometimes, one-way audio. The talk-back channel is almost always a proprietary signalling path in the vendor's app. So the moment you move a doorbell into an NVR, you usually lose the ability to talk to whoever is at the door from that NVR.
If answering the door remotely matters to you, keep the vendor app installed as well. That is normal, not a compromise you should feel bad about.
Network hygiene
Put the doorbell on its own SSID or VLAN with client isolation, and give it a DHCP reservation. Doorbells are the device most likely to be on the outside of your building, and the most likely to be running a firmware you cannot audit.
If your NVR is on the same VLAN, allow only the RTSP port from the doorbell's address to the NVR. Do not rely on the camera's own password alone — plenty of them ship with discovery protocols that answer anyone on the subnet.
Where people get stuck
The stream works in VLC but not in the NVR: almost always a transport setting (TCP versus UDP) or an authentication-in-URL problem.
It works for ten minutes then dies: the doorbell went to sleep, or Wi-Fi signal at the door frame is weaker than you think. A doorbell is mounted through a wall or a metal door frame, which is the worst possible place for 2.4 GHz.
The timestamp is wrong by hours: the device has no NTP configured or no internet access to reach one. Fix that before you try to correlate clips.
Events never fire: you are polling the main stream. Move detection to the sub-stream.
The honest version
A video doorbell is an event device. A security camera is a recording device. They look similar, they are sold in the same aisle, and they are built for different jobs. If you buy the doorbell for the doorbell job and add a separate wired camera for the recording job, everything gets simpler.
I work on the manufacturing side of this category, so I see both sides of this: the returns where someone expected an NVR stream from a battery doorbell, and the support tickets where the answer is simply "use the sub-stream".
Xingliao Smart Home builds smart switches, video doorbells and security cameras on Tuya WiFi and Tuya ZigBee, and runs OEM/ODM programmes from Shenzhen. Factory and ODM capability.
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