Multichannel video signal encoding devices.
Multichannel video encoders are used in IP video surveillance systems for local objects with a high concentration of cameras. Such objects include high-rise buildings, airports, train stations and sports facilities. The main function of these devices is to digitize an analog signal, compress and transmit images (audio signals) over an IP network to various users (operators) and archiving devices (network video recorders).
Features of multichannel IP encoders
Unlike their prototypes — digital video recorders, multi-channel video encoders do not have an image recording function, controls or monitor outputs. Most models do not even have a built-in web interface, which is present in single- and four-channel IP encoders. Setting up and programming multi-channel video encoders is carried out using specialized utilities or directly in the software of the IP video surveillance system. However, there are also common features: the number of channels is a multiple of 2 and, as a rule, is limited to 16 video inputs. A number of manufacturers implement pass-through channels for reconnecting analog video signals from other control devices or image processing. It is possible to connect audio signal sources, there are built-in interfaces for controlling PTZ cameras (RS-232/422/485) and inputs for connecting sensors and actuators. The form factor of multi-channel video encoders is installation in a 19″ cabinet.
As noted above, multi-channel IP encoders are in demand in systems where analog cameras are relatively grouped (installed in close proximity to each other). In this case, the number of cameras is not less than 8. In this case, the use of multi-channel IP encoders is cheaper than IP cameras. These devices are no less relevant for hybrid video surveillance systems or the implementation of an existing analog system into a digital system based on an IP network.
The fundamental difference between multichannel IP encoders and specialized crates (baskets) that allow combining single-channel encoders is that multichannel devices have one, rarely two network interfaces (the second port is used as a backup). Multichannel IP encoders have one IP address and require only one port to connect to the digital network. This feature affects the cost of the system, as it allows saving on the capacity of the network switch to which the IP devices are connected. Here it is necessary to mention another solution of a number of manufacturers of multichannel encoders that allows for an additional reduction in costs — to reduce the cost of the system per channel. We are talking about the possibility of expanding the number of channels by connecting an additional encoder to the main one via the USB2.0 interface. The expansion unit is the same multichannel encoder, having, for example, 4 or 8 video inputs, but without a network interface. Thus, the number of encoder channels can be easily increased without the need to allocate an additional IP address and port on the switch.At the same time, each channel is completely independent — it can be configured and programmed, and scenarios can be created independently. If the device supports several compression codecs, each channel can work with any of them. Ports with interfaces for controlling PTZ cameras, like alarm inputs, can be connected to any video input. Each channel has its own identifier, which allows for full diagnostics.
The only disadvantage of a system based on multi-channel IP encoders compared to single-channel devices combined into a group is its lower reliability. After all, failure of one multi-channel device leads to loss of image from all cameras connected to it. However, a system based on digital video recorders looks even less reliable. A recorder failure often also leads to loss of the archive.
Functional capabilities
Functionally, multi-channel IP encoders are no different from other encoding IP devices, since they use the same processors and software. Well-known MPEG2, MPEG4 and H.264 are widely used as compression algorithms.
To automate the video security process, encoders have video motion detectors. A number of manufacturers build video analytics algorithms into their devices.
Of course, multi-channel IP encoders support a full range of network protocols, taking into account the specifics of the solutions. Perhaps the most important of the protocols used are DHCP, RTSP and Multicast technology. DHCP allows the encoder to automatically obtain an IP address and other parameters necessary for operation in an IP network. The RTSP real-time streaming protocol allows you to receive images for monitoring and recording using various multimedia programs and devices, simplifies the integration process. Finally, Multicast technology, known as multicast technology, allows you to send one copy of the packet to all recipients at once. Thus, adding new clients accessing the encoder does not entail an increase in network bandwidth.
Multi-channel IP encoders are able to work with single-channel decoders — a number of manufacturers support this function for their models. Thus, they are an element of the digital video matrix.
As already mentioned, multi-channel IP encoders are designed for installation in a 19″ cabinet or rack. They are designed not only for indoor installation, but also require maintaining certain temperature conditions. Typically, the operating temperature range is from 0 to +40 degrees Celsius. Also, the devices require a separate power source and do not support PoE technology (power over a network cable). All this is directly related to the more complex and energy-intensive architecture of multi-channel encoders, where a separate image processing processor is allocated for each channel.
In conclusion, it is worth noting that multi-channel IP encoders are one of the elements of an IP system and, depending on the task, IP cameras can be used along with them. In fact, multi-channel encoders are the most cost-effective solution for both IP and hybrid systems. The recording device can be located independently of the location of the encoders or installed in the same room.