JVC VN-V686U - Manual (Page 24)

24
Connection/Installation
● Ensure that there is sufficient network
bandwidth for the data volume to be sent out
by VN-V686U. 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-V686U 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-V686U is
determined by the VN-V686U settings, number of
clients, and the client’s requested number of frames.
The total MPEG4 bit rate from VN-V686U 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 × 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-V686U
The maximum number of distributions for VN-V686U
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 1 Maximum
configurable
value (24 Mbps)
VN-V686WPU_EN.book Page 24 Wednesday, January 16, 2008 10:39 AM