Video Cassette Recording (VCR)
Today, security camera system may consist of many different products and technologies. Many suppliers build pieces of the system, whether it is part of a hybrid analog / digital implementation or an end-to-end networked IP solution. The following sections explain the evolution of the CCTV system, starting with a fully analog system and adding components until it achieves networked capabilities.
A traditional analog surveillance system consists of analog cameras, time-lapse VCRs and monitors. A coaxial cable runs from each camera to a multiplexing device, which allows multiple cameras recording to one VCR, with a monitor for viewing. The time-lapse VCR allows the operator to adjust when the VCR records so the standard two-hour VHS tapes can be used for much longer. The trade-off results in lower-quality images in return for less frequent tape changes or image overwriting.
Analog CCTV recording systems have been the surveillance and monitoring for the past twenty years. This technology is extremely old and outdated and is rapidly being replaced by digital recording technology which now represents over 80% of all new installations.
Digital Video Recording (DVR)
A DVR is a computer with a special video graphics card that connects it to an analog camera via 75-ohm coaxial cable. The card also converges the analog signal to a digital signal and compresses the resulting image so it can be stored on an internal hard drive, viewed or transported across a network. DVRs typically use a computer operating system such as Windows or Linux along with video management system (VMS) software. DVRs are controlled and accessed via keyboards, mice and external monitors in order to setup, run surveillance software and replay stored video. DVRs usually have an internal Ethernet connection for LAN or WAN attachments.
Network-Attached Digital Video Recorder (NDVR)
A Network-attached Digital Video Recorder is part PC and part "Network Appliance" A NDVR is very similar to a DVR and is sometimes called a "Network Appliance" because it does not require-attached keyboard, mouse or video monitor. The device is plugged directly into an Ethernet switch and the only way to access the device is through the network. The device still has an operating system but it resides in firmware burned into a chip on the motherboard. Most of these NDVRs rely on Video Management Software (VMS) loaded on a network-attached client PC, although some have it 'embedded' in another motherboard chip, where it can be accessed from any PC through an Internet Browser. Most of these products have internal hard drives for local video file storage, but they can be inter-connected with Direct Attached Storage Arrays (DAS), Network Attached Storage (NAS) equipment or Storage Area Networks (SANs) through the LAN or WAN.
Network Video Recorders (NVR)
The 'pure' Network Video Recorder (NVR) is not a "turn-key box" or network appliance, but created with a combination of network devices. An NVR can be a standard network server with internal or attached storage capability along with recording software, video surveillance system or communication software and possibly even intelligent video analysis software. Digitization of the analog video is done by a separate 'Video Encoder' or 'Video Server' which is also attached to the Ethernet / IP network. Using an NVR configuration, true IP cameras can act as Video Servers and input images directly to the NVR and be managed directly by the NVR video software.
Video Encoders & Decoders
Encoders are used to take video signals in analog or digital form and make them suitable for transmission where bandwidth or storage capacity is an issue. Encoding applies to many video surveillance system applications where digital recording devices are used or viewing across a network is desired. Analog signals must first be converted to a digital format, but then each source must be compressed into a smaller size file or video "stream." There are several standards for encoding / decoding and compression; each has advantages and disadvantages. Typically the trade-offs are quality for reduced file size.
A decoder is a device that does the reverse of an encoder, undoing the encoding so that the original information can be retrieved. The same method used to encode is usually just reversed in order to decode. These are still relatively simple devices which can be a software program running on a PC, a DVD player or even a cell phone. They may also be hardware devices that take the digital video format and convert it back into an analog signal that can be displayed on a TV monitor. This allows the networked video to become switched across any output device. Usually the decoding and encoding functions reside in the same device and is commonly referred to as a "codec," an acronym for code / decode.
Migration to a Digital Network Solution
Because there is significant financial investment in analog CCTV, many security managers opt for a phased transition to IP, blending both analog and digital security technologies wherever possible during the migration. Integrating existing analog equipment with products that provide the functionality of a digital system offers several benefits:
Remote accessibility
Cost-effectiveness
Flexibility
Scalability
In the simple illustration below, the analog cameras are connected to an analog video switcher, an analog monitor, a VCR and a video server. This traditional setup provides sequential monitoring and recording of multiple analog cameras. By connecting a video server to convert the analogue video into digital data, images can be sent over an Ethernet / IP network (through a router / switch) which provides Ethernet connections for networked IP cameras. With this configuration, authorized security personnel in local or remote locations can view video originating from both analog and digital, networked IPcameras.
In the transition from analog to digital surveillance systems, no system is too small or too tightly aligned to analog technology not to benefit from some measure of digital technology.
In conclusion the migration of a Digital Network Solution to your existing Analogy System can be done and still have the capability to add the latest software and hardware.
Some of the latest in security surveillance system software is the Dual Sensor as listed below in more detail.
The latest camera systems would have been a combination of network camera and high end analogy cameras.
The post Video Surveillance System Devices appeared first on IrresistibleMT.
http://ift.tt/2HIFPky
via IFTTT
No comments:
Post a Comment