In many large surveillance projects, the number of cameras is relatively high. However, bandwidth calculation is often ignored when configuring network switches. As a result, after installation and commissioning are completed, video transmission stuttering and lag frequently occur. Today, we will explain how to calculate camera bandwidth and select the correct network switch.
How to Calculate Camera Bandwidth and Select the Right Switch to Avoid Video Lag
(How does knowing camera bandwidth help determine the correct switch and prevent video stuttering?)
Whether a network switch can meet the transmission requirements of surveillance equipment mainly depends on bandwidth. The higher the encoding bit rate of a network camera, the greater the bandwidth required.
For example, a 3-megapixel camera using H.265 encoding at 25 frames per second has a bit rate of 6000 Kbps, which occupies approximately 5.8 Mbps of bandwidth
(using Smart265 or H.265++ encoding, the bandwidth requirement is about half of standard H.265; H.264 is obsolete and is not considered here).
In actual projects, multiple switches are often cascaded through a single uplink port. The theoretical bandwidth of a Fast Ethernet (100 Mbps) switch port is 100 Mbps, but in practice, only about 70% of this bandwidth can be effectively utilized. Achieving around 70 Mbps in real throughput is already considered good.
For example, assume there are three areas: Area A, Area B, and Area C, where Area C is the central equipment room.
- Area A installs 10 units of 3-megapixel cameras
Required bandwidth: 10 × 5.8 Mbps = 58 Mbps - Area B installs 8 units of 3-megapixel cameras
Required bandwidth: 8 × 5.8 Mbps = 46.4 Mbps
Area B is cascaded to the switch in Area A through a single uplink port.
Although the switch in Area A can independently meet the access bandwidth requirements of Area A, once Area B is cascaded to Area A, the total required bandwidth becomes:
58 Mbps + 46.4 Mbps = 104.4 Mbps
This exceeds the actual carrying capacity of a single Fast Ethernet switch uplink port. Therefore, the switch must be upgraded to a Gigabit switch.
Similarly, since Area C is the central equipment room, it must also be upgraded to a Gigabit switch.