Video surveillance glossary

AI video search

Finding moments in recorded footage by describing them in plain words, such as "a person in a red jacket", instead of scrubbing a timeline or filtering by motion. Read more

Audit log

A record of who did what in a camera system: who changed a camera, who exported footage, who added a user. Useful when footage becomes evidence.

Bitrate

How much data a camera stream uses per second, usually in megabits per second (Mbps). It sets both network load and storage: each 1 Mbps recorded around the clock fills about 10.8 GB a day. Read more

Codec

The method a camera uses to compress video before sending it. H.264 and H.265 are the common ones in security cameras. Read more

DVR

Digital video recorder. A box that records analogue cameras connected by coaxial cable and digitises their video. The IP-camera equivalent is an NVR.

Edge storage

Recording on the camera itself, usually to a memory card, as a backup when the network or recorder is down. ONVIF Profile G covers finding and playing it back.

Frame rate

How many pictures per second a camera records (fps). 12 to 15 fps is enough for most security footage; higher rates mostly cost storage.

GPU

Graphics processor. In a video server it takes decoding and converting video off the CPU, which matters with many cameras or AI search.

H.264

Also called AVC. The video codec most security cameras have used since the late 2000s. Plays almost everywhere.

H.265

Also called HEVC. The successor to H.264, typically needing 30 to 50% less bitrate for a similar picture, at the cost of more processing to play. Read more

HLS

HTTP Live Streaming. Delivers video as a series of short files over ordinary HTTPS. Very reliable through firewalls, but usually several seconds behind live. Read more

Incident

A recorded event worth keeping: the clips from every camera that saw it, with a priority, a status and notes, ready to hand over.

Infrared (IR)

Light invisible to the eye that cameras use to see in the dark. IR footage is black and white, so colours can't be searched for at night.

IP camera

A camera that sends digital video over a computer network, rather than an analogue signal over coaxial cable. Most new security cameras are IP cameras.

Keyframe

A complete picture in a video stream; the frames in between only store what changed. A keyframe every one or two seconds lets playback and stream switching start quickly.

Main stream

A camera's full-quality video stream, used for recording and full-screen viewing. Read more

Motion detection

Flagging when pixels change in part of the picture. Good for empty spaces; noisy outdoors, where trees, rain and headlights all count as motion.

NTP

Network Time Protocol. Keeps every camera's clock in step, so timestamps line up across cameras and stand up as evidence.

NVR

Network video recorder. A box with disks and software that records IP cameras, usually with a fixed number of channels. Read more

ONVIF

An open standard that lets cameras, recorders and software from different makers work together: discovering devices, reading their settings and finding their video streams. Profile T is the one to look for on new cameras. Read more

PoE

Power over Ethernet. Powers a camera through its network cable. Standard PoE (802.3af) supplies up to 15.4 W per port and PoE+ (802.3at) up to 30 W, so a switch has a total power budget to watch.

PTZ

Pan-tilt-zoom. A camera that can be steered and zoomed remotely, which works best with low-latency live video.

Retention

How long recordings are kept before the oldest are deleted to make room. Thirty days is a common default; local rules may set limits. Read more

RTSP

Real Time Streaming Protocol. How nearly every IP camera delivers its video, usually on port 554. Each stream has its own rtsp:// address. Read more

Self-hosted

Also called on-premise. Software that runs on hardware you control, so recordings stay in your building rather than in a provider's cloud. Read more

Smart codec

A maker's extra compression on top of H.264 or H.265 that lowers bitrate when the scene is still, such as Axis Zipstream or Hanwha WiseStream.

Subnet

A range of addresses on a local network, such as 192.168.1.0/24. Camera discovery usually only finds devices on the same subnet. Read more

Substream

A camera's second, much lighter stream, sized for grids of many cameras and slow connections. Read more

Transcoding

Converting video from one format or size to another, for example so a device that can't play H.265 can still show the camera.

VMS

Video management software. The software that runs a camera system: it connects to cameras, records them, shows them live and lets you find and export footage. Read more

WebRTC

The real-time video technology behind video calls. Delivers live camera video in well under a second, encrypted by design. Read more

WS-Discovery

The multicast message (UDP port 3702) that ONVIF uses to find cameras on the local network without knowing their addresses. Read more