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appendix
68_ appendix
TERMINOLOGY
GOP : You can set between 5 and 15 for the MPEG4 and H.264 CODEC.
The default is 15, and if set to 15, one I-Frame will be output per 15 frames as one I-Frame
and 14 P-Frames constitute the GOP.
The lower the GOP size is, the better the quality is; however, the bit rate as well as the data
size will increase, causing a lower of the fps. GOP(Group of Pictures) is a set of video frames
for MPEG4 and H.264 format compression, indicating a collection of frames from the initial
I-Frame (key frame) to the next I-Frame. GOP consists of 2 kinds of frames: I-Frame and
P-Frame. I-Frame is the basic frame for the compression, also known as Key Frame, which
contains one complete image data. P-Frame contains only the data that has changed from
the preceding I-Frame.
Entropy coding : Data transfer technology used to reduce the compression loss from encoding.
CAVLC (Context-adaptive variable-length coding): Records a higher compression loss
rate than CABAC.
CABAC (Context-adaptive binary arithmetic coding): Shows a lesser compression loss than
CAVLC.
Bitrate Control
CBR(Constant Bitrate)
This will transfer video data in an equal size at all times, regardless of the video
complexity. The video quality may be deteriorated, depending on the video complexity.
VBR(Variable Bitrate)
The amount of video data to transfer may differ, depending on the video complexity. This
enables receiving video data in an equal quality at all times.
TTL : TTL stands for “Time To Live”, which you can specify to prevent loss of data packet that
passes through multiple-staged routers. Each router decreases the TTL value by one each
time a packet passes it through; If the TTL value reaches 0, the packet cannot further pass
through a router.
TCP : It is a general purpose protocol used for transmission that requires reliability. With
constant communication between the sender and recipient, it provides high reliability against
transmission data loss; however, it has imitation to transmit a large amount of data in real time
at a high speed.
It enables reliable data transmission over xDSL and cable network at a relatively slow speed.
UDP (Unicast): It refers to a system that transmits data between only one transmitter and one
receiver (1:1).
UDP (Multicast): It refers to the data transfer protocol in one-to-many (1:N) between the trans-
mitting and receiving terminals; although it alleviates the network load, it requires <Multicast>
router.
For more information such as whether the network over which the camera is installed sup-
ports <Multicast>, contact the network administrator.
UDP :
It is a protocol appropriate to transmit a large amount of data such as multimedia data at a
high speed. However, with its nonconnection structure, it records a higher transmission efficiency
than TCP especially in a high LAN environment faster than 100Mbps.
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