The security
system is an intrusion alarm system, a video security monitoring system,
an entrance and exit control system, an explosion-proof security
inspection system, etc., which are constructed by using security
products and other related products for the purpose of maintaining
social public safety; or by combining these systems as subsystems to integrate electrinic system or network. According to the <12th Five-Year Development Plan of China's Security Industry>, as of
2010, the total output value of China's security industry reached more
than 230 billion yuan, of which the output value of security products is
about 100 billion yuan. According to the estimate for the doubling of the industrial scale during the period, the total output value of the security
industry in 2015 will reach 500 billion yuan. As an important
part of the security system, the video surveillance system has occupied
more than half of the domestic security industry market share due to the
continuous expansion of its application fields and the continuous
expansion of the industry. This article focuses on the evolution of video surveillance.
Four stages of video surveillance development
With the
continuous integration of computer multimedia technology, coding
compression technology, network transmission technology, storage
technology and video surveillance, the development of video surveillance
has experienced the evolution of digital remote monitoring system,
digital remote monitoring system, network video surveillance, and
high-definition video surveillance. The functions, form and composition of video surveillance have undergone tremendous changes.
Digital remote surveillance system phase
The digital
remote surveillance system began in the 1970s. At this stage, the analog
camera was mainly used for video signal acquisition, and the video
signal was transmitted to the matrix host or display and recording
device through the coaxial cable. In the digital
remote surveillance system, the switching control device based on
analog matrix and analog keyboard, while
the display and video recording equipment adopts monitor and video
cassette recorder (VCR, VideoCassetteRecorder).
Digital remote
monitoring system (CTV), also known as Closed Circuit Television (CCTV),
consists of analog cameras, video splitters, analog matrix, control
keyboard and video tape recorder (VCR), which can realize basic
functions like monitoring, video recording and playback. Mainly used coaxial cable
(75Ω, 1.0Vp-p) to transmit composite video
broadcast signals (CVBS, CompositeVideo BroadcastSignal).
Digital remote surveillance system phase
The digital
remote surveillance system began in the late 1990s. At this stage, the
analog signal collected by the analog camera was mainly used for
analog-to-digital conversion, encoding, and compression by video compression card, and the PC was
used for local storage. The DVR at this
stage adopts PC-based architecture, which mainly realizes analog signal
digitization and video encoding, compression and storage functions. The
functions in network transmission, software application, matrix control,
etc. are not perfect, so usually work with analog matrix in application.
PC-DigitalVideoRecoder
(PC-DVR) was born in the initial stage of the digital remote surveillance
system era. It provides a reliable guarantee for the digital remote surveillance system to successfully complete the digitalization of analog
signals, and effectively solves the digital remote surveillance system
video storage Limitations of media and storage cycles. The digital
remote monitoring system is mainly composed of analog cameras, PC-DVR, monitors, etc. It can realize basic functions such
as monitoring (monitoring), recording, playback, alarm linkage, voice
intercom, real-time control and so on.
In addition to
the digital-to-analog conversion, encoding and compression of the
front-end analog signals, the PC-DVR can also
realize the local storage of compressed data. The signal transmission
medium is still a coaxial cable (75Ω, 1.0Vp-p).
Network video surveillance phase
Network video
surveillance began around 2005. At the beginning of this phase, the
embedded network hard disk recording (E-DVR, Embedded Digital
VideoRecoder) or embedded video server (DVS, DigitalVideoServer) was
used to digitize, encode, compress and access the network, realized implement networked video surveillance. With the
continuous deepening of the construction of safe cities and the
continuous expansion of video surveillance in financial and other
industries, the demand for video surveillance networking has become
increasingly apparent, which has had a positive impact on the
development of video surveillance networking. At present, China's video surveillance industry has basically realized network video surveillance.
1. Network video surveillance with analog access mode
In daily
applications, if the video resolution requirement is not very high in a small
surveillance scenario, an analog solution may be used, that is, an
"analog camera + DVR + monitor + PC (client)" architecture. In this kind
of architecture, the front end usually adopts the standard definition
analog camera to realize the acquisition of the video signal, and
transmits it to the DVR through the coaxial cable for encoding and
storage, and the DVR can be connected to the monitor for real-time
preview and playback operations. In this solution, the DVR connect to the network, and the client can remotely access the DVR for remote operation.
2. Network video monitoring of analog-to-digital hybrid access mode
The signal of
the front-end analog camera can be directly transmitted to the surveillance system center, or by placing a video encoding device close to the
front-end device, digitizing, encoding, and compressing several analog
video signals into packets that can be transmitted over the network (or
wireless to surveillance center directly. In the surveillance center, the analog signal is connected to the analog matrix
through the video distributor, and the digital signal is converted into
an analog video signal to the analog matrix through the video decoding
device, and all the video and audio data are stored in the hybrid hard
disk recorder (H-DVR).
HD video surveillance stage
After the
networked surveillance is satisfied as a basic application, the desire to
see the details of the face, license plate and other details has shifted
the user's attention to the improvement of video clarity, and HD video
surveillance has begun to emerge.
In order to
realize high-definition video surveillance in true sense, all
aspects of acquisition, transmission, storage, decoding, display and
control have strict requirements and are indispensable. China's video
surveillance industry is still in the initial stage of high-definition
video surveillance, and the trend of high-definition will continue for a
long time.
1. HD video surveillance with full IP access
High-definition surveillance of all-IP access mode is one of the most typical application modes. In this architecture, video and audio data is transmitted over IP networks in the form of IP packets.
Front-end: After
the video image acquisition by the network HD camera, then
encoding compression and transmitted back through the network, in addition,
signals such as alarms and sounds can be connected to the camera for
back-transmission.
Transmission: Data transmission is connected through the Ethernet layer.
Storage: The video streams are all encoded into digital signals, they can be stored via NVR, NAS or IPSAN.
Display: The
front-end video source can be decoded by the decoder to display on wall to completed the operation of rounding and switching control.
Control: The
corresponding operation can be completed by the keyboard control decoder
or the front-end dome, pan/tilt and other devices.
Management: All devices can be managed by the client and linked with alarms, sounds and other signals.
2. HD video surveillance with full digital access
In general, the high-definition surveillance mode by using all-digital access method is relatively less.
Front-end: The
signal transmitted by the camera is uncompressed bare data collected
from the image sensor. It has advantages over the network camera in
terms of image detail, color reproduction, and control delay, but the
cost is high.