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Q1 : What is a video
server?
The term
"video
server" refers to a network-attached
server for video that is connected
to a computer network like a LAN. A
video server can deliver live video,
automatically or on request, to a
browser or other professional
security applications. Security
systems have traditionally been
based on analog CCTV (closed-circuit
television) technology. Video
servers digitize analog video
sources and distribute digital video
over an IP network ??turning analog
cameras into IP cameras. A video
server can also be connected via a
modem for access over a phone or
ISDN line.
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Q2 :
What's the advantage using MPEG-4?
MPEG-4 provides DVD
quality video, but uses lower bit
rate so that it?s feasible to
transmit digitized video streams in
LAN, and also in WAN, where
bandwidth is more critical, and hard
to guarantee. MJPEG's bandwidth
requirement is a little bit more
than MPEG-4, while its resolution
and frame rate are much worse.
MPEG-2 can provide DVD-like video,
just like MPEG-4. However, MPEG-2's
bandwidth requirement is so high
that it?s not possible to use in a
LAN or WAN environment.
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Q3 : Why
is MPEG-4 ASP Compliant important?
Is ASP same as Short header as some
other manufacturer claims?
There are MPEG-4 ASP
(Advanced Simple Profile), MPEG-4 SP
(Simple Profile), and MPEG-4 Short
Header in the market now. MPEG-4 ASP
provides all I, B, P frames and
therefore provide better compression
rate, while both MPEG-4 SP and
MPEG-4 Short Header provide I and P
frames only. In current practice,
MPEG-4 ASP and SP are deployed by
ASIC, while Short Header is most
commonly deployed by DSP. For the
same video quality, the bandwidth
required for MPEG-4 ASP is smaller
than that of MPEG-4 SP or Short
Header.
Here is a video
quality comparison between ACTi's
video server and a competitor's
MPEG-4 video server. It?s obvious
that although both video servers use
MPEG-4 compression technology, ACTi's video server has better video
quality since ACTi is MPEG-4 ASP
compliant, while the competitor is
MPEG-4 Short Header compliant. The
right-hand picture is ACTi's video,
while the left-hand one is from the
competitor.
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Other Product
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MPEG-4 Short header
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Resolution : CIF
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BitRate : 384kb/s |
ACTi SED-2100R
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MPEG-4 ASP
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Resolution : CIF
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BitRate : 384kb/s |
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Q4 : What's
the advantage to use MPEG-4 ASIC over DSP?
Current most popular
DSP cannot provide enough processing
power to process MPEG-4 full D1/30
fps encoding algorithm. The video
quality processed via DSP cannot
compete with that processed by ASIC.
Current DSP usually supports up to
CIF (360x240) right now, while ASIC
can support not only CIF, but also
full D1 (720x480).
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Q5 : Why
is it so important to have DDNS support?
If an IP camera can
support DDNS (Dynamic Domain Name
Server), users can set the IP camera
at a virtual domain name (such as
cam1.kitchen.Taipei.xxx.xxx) at
dynamic IP, and be able to view this
IP camera anywhere that has access
to the internet. It saves money when
setting up the broadband with
service provider, whether it?s ADSL
or cable modem, since fixed IP is
not a must.
Some IP camera manufacturers claim
to provide DDNS. However, they are
software solution that needs to be
installed at client site?s PC.
Therefore, it requires users to see
those IP cameras at the PCs that
have installed the specific AP from
manufacturers. This is not as
user-friendly. ACTi have DDNS
function built-in the IP camera so
that users can view the IP camera
from anywhere.
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Q6 :
What does "Digital Time Code
Embedded" means? Why is it
important?
The "Digital Time
Code Embedded" function is embedded
in MPEG data stream. Therefore,
the exact time each frame is
recorded will be stored. It is very
useful when users want to find the
video at an exact time or a certain
time interval. If an IP camera
doesn?t support this function, users
have to search for the whole video
stream by looking through the video,
which takes a lot of time. Some
cameras provide software solution to
simulate this function. However,
this is not as accurate. Video
streams with Digital Time Code
Embedded are so-called "Smart
Video", and can enable a lot of
useful applications at client site.
The other advantage of Digital Time
Code Embedded is that it provides
watermark on the video streams.
Since the time code is written in
the video stream, if the video is
modified by others, the time code
will disappear from the video
stream, and therefore, the time code
can act like a watermark for the
video stream and users will find if
the video is modified by
unauthorized people.
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Q7 : Why
is it important to have WAN and LAN
on the video server?
ACTi's video servers
provide two RJ-45 connectors. One is
WAN and one is LAN. Both of them are
10/100. The difference between a WAN
and a LAN is that WAN is to be
connected to the internet, while LAN
is to be connected to a local
network. Since the internet'?s
bandwidth is very critical, ACTi
provides hardware QoS (Quality of
Service) on the WAN port to ensure
the bandwidth when uploading video
streams through the internet. Also,
the WAN port is equipped with PPPoE
(Point-to-Point Protocol over
Ethernet) which enables the video
servers to be connected to an ADSL
or cable modem without the need to
go through a router first. If the
video servers are to be deployed at
a large area, it will be very costly
to provide routers to each video
server. Using video servers with
PPPoE built-in, installers will be
able to save a lot of cost over
routers.
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Q8 :
What kind of software is provided by
ACTi together with video server?
ACTi will provide SDK
(Software Developer Kit) along with
a simple AP for reference.
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