You're not alone if you believe that even a small network surveillance camera system could overwhelm a company's bandwidth, making it an ineffective pipeline for security. Despite evidence to the contrary -- such as installations where thousands of video channels stream over a single network -- confusion and apprehension often dominate common sense when it comes to separating fact from fiction regarding bandwidth consumption. Part of the problem stems from the variables used to calculate bandwidth specifically for surveillance video alongside performance levels of the networking equipment we install.
To provide clarity, this article explores the variables affecting bandwidth consumption, including ways to employ some of the latest advances in Ethernet standards to help both security and IT professionals make intelligent decisions regarding video surveillance installation choices.
Getting to the source of bandwidth misconceptions
At Interop 2011, the premiere technology tradeshow for the networking industry, it was obvious to me that most networking professionals believe that video on the network consumes far too much bandwidth. So, when security professionals recommend deploying higher quality, IP-based surveillance solutions, IT departments immediately refuse to support the project. Looking at the performance levels of switching equipment as well as the bandwidth consumption of today's networked surveillance cameras, one wonders how they could have reached this conclusion. So I asked them.
It turns out that their perception was based on external sources such as YouTube, CNN.com and other sites that deliver downloadable content. Network professionals cringe at events like the recent Royal Wedding and basketball's March Madness tournament because they know hordes of employees will stream live video or download highlights. The operative word is "download," which points to a very different technical reality than what is created by surveillance content.
A company's connection to the Internet is typically smaller than the bandwidth available across its local area network (LAN) – usually at least 10 times smaller. What IT is really concerned about is the download speed from the Internet, which typically has nothing to do with internal video surveillance activity. From their perspective, it's a budget issue of how big a pipeline they can afford. In contrast to hordes of employees simultaneously downloading content from the Web, surveillance video is a LAN activity viewed by a limited group of authorized viewers and therefore shouldn't cause IT professionals anxiety about overwhelming the pipeline.
Calculating network requirements for video surveillance
Scoping out the bandwidth requirements for a surveillance system begins with defining your viewing and recording needs. These viewing and recording requirements differ in many cases, often resulting in dual-streaming solutions that factor significantly into the overall amount of bandwidth consumed. In each case you need to specify the resolution and the images per second to be viewed and/or recorded. With a few exceptions, the de facto standard for compression has become H.264. But the bit rate will fluctuate depending on the amount of motion in the scene.
To help you figure out how much bandwidth you might need, let me walk through a scenario using the bandwidth calculator from my employer Axis Communications. That calculator can be found online at www.axis.com/products/video/design_tool/calculator.htm.
The scene I've chosen contains hundreds of people exiting a train platform during rush hour. The video is to be viewed and recorded in 720p which amounts to 1280x720 resolution. I've selected 18 frames per second for both viewing and recording. To put it into perspective, this is the same viewing experience that most of us see while watching the Super Bowl. Using advanced H.264 compression, I've calculated a total bandwidth consumption of 8 megabits per second (Mbps) which is derived by adding the viewing and recording bandwidths together. Assuming the camera is attached to a 100 Mpbs network switch, this means only eight percent of the total available bandwidth will be dedicated to that camera.