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Connection/Installation
●
Ensure that there is sufficient network bandwidth
for the data volume to be sent out by VN-
V686WPU. 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-V686WPU 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-V686WPU is
determined by the VN-V686WPU settings,
number of clients, and the client’s requested
number of frames. The total MPEG4 bit rate from
VN-V686WPU 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 to 8000 kbps)
Restrictions on the Number of
Distributions for VN-V686WPU
The maximum number of distributions for VN-
V686WPU is determined by the settings as well as
requirements from the client.
When only JPEG images are distributed, the
maximum number of distributions is determined based
on the highest bit rate within the stream. When a
distribution request that exceeds the maximum
number of distributions is received, this request is
denied. For example, if Client A requests for and
receives data at 1 Mbps, while Client B requests for
and receives data at 5 Mbps, the maximum number of
distributions is 4 streams according to the table below.
Maximum number of distributions when only
JPEG data is distributed
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 to 100
KB
Selectable
between
3 KB to
33 KB
Distribution at
maximum bit
rate
Maximum
number of
distributions
Total
maximum bit
rate
1 Mbps and
below
20 20 Mbps
5 Mbps and
below
4 20 Mbps
10 Mbps and
below
2 20 Mbps
Larger than 10
Mbps
1Maximum
configurable
value (24 Mbps)
VN-V686WPU_EN.book Page 24 Friday, February 8, 2008 5:20 PM