Why does an IP camera Lag

Issue

Network camera latency issues.

Product Line

Pelco Cameras

Environment

  • All IP Cameras

Cause

  • Sales Support

Resolution

From the operator’s point of view, latency is the time lag between the camera and the display.

Between camera and display, a video signal goes through multiple processes, each of which is a potential source of latency. To address latency effectively, it’s helpful to understand the path that video follows.

Video capture is the first step, and it takes place at the camera. Once the camera’s lens and imager capture the image, the image must be encoded using a video codec to create a data stream (i.e., MJPEG, MPEG-4, H.264). This encoding takes place inside an IP camera, or if the camera is analog, inside a video encoder. The power of the encoding processor and the choice of video codec play a major role in how quickly this processing takes place. The slower the encoding, the more latency is introduced.

Once encoded into a data stream, the encoded video travels along the network. Like any network traffic, a video data stream is segmented into packets, which go across a network and then are reassembled at their destination. Network traffic introduces its own measure of delay as packets are routed. Obviously, the design of a network will have an impact on how quickly and efficiently data moves on it.

Once all of those video data packets reach their destination, they must be reassembled, in proper order and decoded into a format that can be viewed on a monitor or display. This step takes place at a decoder. Just as with the encoder, the power of the processor and the choice of codec significantly impact the efficiency of this step. One important note about decoding – it’s harder than encoding. And as more megapixel cameras start flooding networks with their larger datastreams, decoders will have even more heavy lifting to do.

Once decoded, the video streams travel to a display to be viewed. Increasingly, displays in todays video security control rooms are LCD monitors. While LCDs offer many benefits over traditional CRT displays, LCDs do introduce a bit of latency as well, as the decoded video must be deinterlaced before displaying.

Finally, if an operator is “driving” the system with a keyboard and joystick, that keyboard controller can introduce some latency when it sends its control signals across the network.

Video lag from 1-4 seconds can be the average expectation.