Specifications

Security and surveillance
Digital video recorders (DVRs)
www.digikey.com/maxim-industrial 115
Digital video recorders (DVRs)
Overview
Analog CCTV security systems are
moving to digital technology, and
video recording is leading this
transition. The analog VCR has
been replaced by digital video
recorders (DVRs) in security systems
that require video monitoring and
recording. DVRs now offer over-
whelming advantages over analog
VCRs in security applications. Video
footage can be digitally recorded,
processed, and streamed over digital
networks at virtually any level of
image quality, including high defini-
tion (HD). Users now make use of
digital-only technologies such as
real-time analytics, scene search,
motion- and activity-detection
alarms, and remote access over
IP networks. The cost of storage
capacity on physical media such
as hard disk drives (HDDs), digital
versatile discs (DVDs), or network-
attached storage (NAS) is a small
fraction of analog tape-based
recording cost. The use of digital
video recording and archiving also
offers permanent storage of video
footage with no loss of image quality
over time. All of these factors have
driven the security industry toward
adopting DVR as the standard for
video recording.
DVR types
The security market has evolved
into multiple segments for DVR
systems. Embedded, hybrid, and
PC-based DVRs all require the
essential elements of video and audio
capture: analog-to-digital conversion,
compression, playback, and network
streaming. The embedded DVR is
a stand-alone piece of equipment
that accepts analog CCTV camera
inputs for compression and storage
on a local HDD. Hybrid DVRs accept
analog CCTV and IP camera inputs
as video sources. PC-based DVRs are
integrated into surveillance stations
with hardware compression add-in
cards or software compression
running on the PC. The distinguishing
features among different models are
the number of video input channels;
compression standards supported;
video quality of the record, stream,
and display modes; storage capacity;
and how many functions the system
can perform simultaneously.
Video-compression
technologies
H.264 is the new industry standard
for video compression in security
DVRs. Prior generations used
MPEG-4 and even MJPEG for video
recording. H.264 has the advantage
of offering the highest compression
ratio, while maintaining excellent
video quality for security applica-
tions. H.264’s higher compression
ratio (up to two times better than
prior-generation technology) effec-
tively increases storage capacity by
100%, producing smaller file sizes
and, therefore, longer recording time
on a fixed-capacity storage device.
In addition, the use of H.264 allows
high-quality images to be transmit-
ted over networks at very low bit
rates. Security systems that involve
multiple cameras can quickly exceed
ETHERNET
4 A/V INPUTS 4 A/V INPUTS 4 A/V INPUTS 4 A/V INPUTS
HD DISPLAY
PPC AND PERIPHERALS
HOST BUS AND GLUE LOGIC
FPGA AND MEMORY
ANALOG AUDIO/
VIDEO FRONT-END
POWER
SUPPLY
SERIAL
INTERFACE
CLOCK
SPEAKER
OR
HEADPHONES
MEMORY MEMORY MEMORY MEMORY MEMORY MEMORY
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
H.264 CODEC
4 D1 ENCODERS
4 CIF ENCODERS
HDDs
H.264 CODEC
8 D1 DECODERS
H.264 CODEC
8 D1 DECODERS
OSD
ANALOG AUDIO/
VIDEO FRONT-END
ANALOG AUDIO/
VIDEO FRONT-END
ANALOG AUDIO/
VIDEO FRONT-END
FPGA
AUTHENTICATION
AUDIO
USB
PROTECTION
MAXIM SOLUTION =
Functional block diagram of a security DVR system. For a list of Maxim's recommended solutions for security DVR designs, please go to: www.maxim-ic.com/DVR.