In modern times, remote monitoring network, bring the demand video camera,
network server, and the rapid development of the market and the traditional
network video camera operation environment, is the important distinction between
the signal transmission medium is different, video camera through traditional
line, twisted-pair cable or optical fiber transmission, video signal is termed
"road" line, almost no bandwidth constraints, and network video camera and
network server is through the network transmission, ordinary Inertnet lines,
bandwidth, only a few hundred K M (common to 512K behavior, ADSL line 2M), and
under the behavior of a route to use multiple video signal while preaching, the
bandwidth constraints appeared right away. When choosing so thenetwork camera,
the network video server, it is the need to pay attention to the code rate
(bandwidth rate), because it is the network video monitoring system bottlenecks.
Internet video camera, network server code rate of many factors, including
compression method, resolution, graphics, picture frame, the complexity and
image variations, etc. These factors can be divided into the internal factors
and external factors, YiErSen shenzhen science and technology limited company
for you to make a detailed analysis.
Internal factors related with the product itself () :
1 and compression way: with hard disk video recorder, network video
camera, network server compression mainly have M - JPEG, mpeg-4, h.264, M - the
three basic eliminated, only JPEG now use only spare products, using mpeg-4 is
now, because the prices of many h.264 of cheaper, and h.264 in the same quality
situation, bitrate is about to mpeg-4 70%, of course, some high cost will be
compressed chips.
In addition, even the same way, different manufacturers compressed
code-rate also exist obvious difference, such as the h.264 compression standard
has many rules, each manufacturer can simplify part rules to reduce cost, but
also the image compression efficiency by corresponding impact.
2, the resolution ratio and resolution: code is proportional to the
relationship. Network video camera, network server mainstream resolution have D1
(704 576) and CIF (x x 288 352. D1 respectively with equivalent DVD VCD CIF, the
definition of the code rate is CIF D1 four times, so usually have widely
application or CIF resolution.
3 and frame rate: the picture frame rate namely, bitrate fluency and frame
rate is directly proportional to the relationship. The picture is completely
fluent 25 frames per second. Network product frame rate is adjustable, we can
cut through the frame rate to decrease rate, generally transferred to 10 ~ 15
frames can be both rate and fluency, without the requirement for the pictures
looked circumstance, can be more low rate adjustment.
4 and graphics (compression ratio) : network video camera, network server
graphics (compression ratio) is adjustable, quality better code rate is higher,
the user can be adjusted according to their own requirements. Because each
manufacturer of quality (compression ratio) and the parameters of the unit, so
use uniform here to provide reference inconvenience.
External factors (with the product itself, depending on the control) :
Images 1, complexity and the picture code rate: is proportional to the
complexity of the relationship, such as lens side white wall, the rate is very
low, but to a flower, bitrate will soon become high, there are usually several
times.
2, the dynamic change: picture code-rate and pictures in proportion to
change, such as the object of a stationary camera, the rate is very low, but to
the activities of the crowd, bitrate will soon become tall, are most of ten
times.
More detailed analysis for the influence of many factors, streaming user
how should choose?
First need to select compression. Generally speaking, the h.264 products
than mpeg-4, not only, and low bit rate in the picture processing technology and
integral function, the corresponding do more fastidious, of course the price
will be expensive. But for now, I companies or bandwidth to recommend to use
h.264 products.
For the resolution of the network cameras, CIF resolution has can satisfy
the requirements of most situations, although D1 clarity, indeed, but once
streaming over four times, need enough to support the network bandwidth,
otherwise the picture will become very smooth. Of course, if only in LAN using,
generally can ignore the bandwidth of the problem.
Another due to the different network video camera, traditional product
status hasn't toward the homogeneity, manufacturers of products, function and
performance are large, so the user must not only see the price, should choose
the strength and reputable manufacturer, the code rate, quality products,
function and the humanized factors for software.
Use the camera, network to the resolution and frame rate, compression
rationally set to image and bandwidth rate of balance.
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