JVC VN-V25U - Manual (Page 24)

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Connection / Installation
● Ensure that there is sufficient network
bandwidth for the data volume to be sent out
by VN-V25U/26U. Do not send multicast
stream that exceeds the bandwidth. If the
entire bandwidth is used by the multicast
stream, control of this camera via the network
may fail.
● Data volume to be sent by VN-V25U/26U varies
with the settings and number of distributions.
● The maximum bit rate for transmission is
about 20 Mbps.
Estimation of Total Bit Rate
The total JPEG bit rate from VN-V25U/26U is
determined by the VN-V25U/26U settings,
number of clients, and the client’s requested
number of frames. The total MPEG4 bit rate
from VN-V25U/26U is determined by the number
of distributions. Develop a design upon taking
the above into consideration.
Bit Rate of JPEG Stream
The JPEG file size per frame varies with the
encoding settings as well as input video signals.
The following table may be used as a reference.
When VFS is selected, the quantization table
during JPEG encoding will be maintained, and the
file size will increase/decrease according to the
input signals. When AFS is selected, encoding will
be performed such that the target file size is the
average size of multiple JPEG images.
The maximum number of distributions varies
with the bit rate settings as well as the client’s
requested frame rate. Up to 20 streams can be
distributed (including multicast). The total frame
rate refers to the sum of these frame rates.
For example, when 10 fps is requested by two
clients, and in addition, multicast is transmitted
at a rate of 10 fps, the total frame rate will be:
10 + 10 + 10 = 30 fps
If the JPEG file size per frame is 30 KB, then the
total bit rate will be:
30 KB x 30 fps = 900 KB/s = Approx. 7.2 Mbps
Bit Rate of MPEG4 Stream
You can select either the Variable Bit Rate
(VBR) or Constant Bit Rate (CBR) system for
MPEG4 stream.
When the VBR system is selected, the bit rate
varies according to the condition of the input video
signals. The VBR system delivers a stable picture
quality, but forecast of the bit rate is difficult.
When the CBR system is selected, encoding is
performed at a fixed bit rate regardless of the
condition of the input video signals. The picture
quality varies under the CBR system, but the bit
rate can be easily forecast.
You can specify an estimated bit rate for both
VBR and CBR. (64 kbps - 8000 kbps)
Bit Rate of Audio (VN-V26U only)
Up to 2 audio data streams can be sent by VN-
V26U.
Only 1 audio data stream can be recieved. Data
volume for 1 audio stream is 64 kbps. Audio data
volume may be calculated using the following
formula.
64 kbps x no. of streams
The number of streams is the total number of
streams sent via TCP (number of clients), streams
sent via multicast, and stream received by
VN-V26U.
(Example)
When VN-V26U sends out 2 audio streams and
receives 1 audio stream, data volume will be as
follows.
64 kbps x 3 = 192 kbps
Network Requirements
Picture Quality
Control Method VGA File
Size QVGA File
Size
VFS
(Variable
File Size) 1 (High) 80 KB 27 KB
2 60 KB 20 KB
3 40 KB 13 KB
4 (Medium) 30 KB 10 KB
5 25 KB 8 KB
6 20 KB 7 KB
7 (Low) 15 KB 5 KB
AFS
(Average File Size)
Selectable
between
10 KB -
100 KB Selectable
between
3 KB -
33 KB
VN-V25U_26U_EN.book Page 24 Monday, January 21, 2008 10:13 AM