ANPR questions & answers
Answers for the systems around number-plate recognition.
Practical, vendor-neutral guidance for cameras, NVRs, VMS platforms, access control and metadata integrations.
These are general industry answers, not product support. Setting up ANPR Edge? Read the camera connection guide.
8 answerin camera
Why does my Hikvision ANPR camera show video on a third-party NVR, but no license plates?
Video feeds and ANPR metadata are transmitted using completely different network protocols. While your third-party NVR can receive the standard video feed via ONVIF Profile S or RTSP, Hikvision transmits its license plate text and vehicle metadata using proprietary ISAPI or ISUP payloads that non-Hikvision NVRs cannot decode.
Hikvision ISAPI Event Notification Integration
Why does my ANPR camera capture plates perfectly during the day but fail completely at night?
Nighttime ANPR failures are overwhelmingly caused by "IR blooming" and slow shutter speeds. The camera's infrared light reflects too intensely off the retro-reflective coating of the license plate, turning it into a solid glowing white rectangle, while slow shutter speeds cause moving vehicles to severely blur in low light.
ANPR Watch: Minimising False Positives
Can a Uniview (UNV) NVR perform Smart Plate Search with a third-party ANPR camera?
No. Uniview explicitly locks its advanced metadata analytics, including Plate Comparison and Smart Vehicle Search, to its own Uniview-branded LPR cameras. Third-party cameras can only provide basic, unsearchable video streams to the UNV NVR.
Uniview NVR516-64E Datasheet Specifications
How do I get Hikvision ANPR plate data via the HTTP API?
Many integrators discover that recent Hikvision firmware has deprecated traditional GET polling endpoints for plate data. Instead of polling the camera, you must configure the camera's HTTP Listening Server to actively push multipart XML payloads to a designated TCP server whenever a plate is detected.
Hikvision ISAPI Event Notification Integration
Why did my Dahua ANPR HTTP API stop working after a firmware update?
In recent firmware updates (late 2023 onward), Dahua intentionally deprecated and removed the local unencrypted HTTP/CGI endpoints that developers traditionally used to extract license plate events. This breaks custom third-party integrations that rely on these legacy scripts.
IP Cam Talk: Dahua Firmware Warning
How do I configure Vaxtor VaxALPR events with Axis cameras?
To send license plate data from a Vaxtor on-edge application to third-party systems or local relays, you must utilize the Axis VAPIX/ONVIF event framework. This bridges the gap between the Vaxtor OCR engine and the Axis OS action rules.
VaxALPR On-Camera Axis Integration Guide
Why is the ZKTeco LPR camera relay not opening a boom barrier?
When a ZKTeco camera detects a whitelisted plate but the boom barrier fails to open, the issue often lies in the wiring architecture. If you are integrating via Wiegand to a ZKTeco Security Relay Box (SRB) instead of direct GPIO wiring, you must ensure the camera is outputting an encrypted signal.
ZKTeco Security Relay Box Specifications
How many pixels are required for accurate license plate recognition?
Installers frequently mount wide-angle cameras assuming 4K resolution guarantees readability, but OCR engines require a strict Pixels-Per-Meter (PPM) density. A standard 12-inch (0.5m) wide license plate must occupy an absolute minimum of 100 horizontal pixels across the image sensor to ensure reliable character segmentation.
Plate Recognizer: LPR Camera Resolution Guide
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