Network Requirements

●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/26Uvaries 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/26Uis determined by the VN-V25U/26Usettings, number of clients, and the client’s requested number of frames. The total MPEG4 bit rate from VN-V25U/26Uis 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.

Picture Quality

VGA File

QVGA File

Control Method

Size

Size

 

 

 

 

VFS

1 (High)

80 KB

27 KB

(Variable

 

 

 

2

60 KB

20 KB

File Size)

 

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

 

Selectable

Selectable

 

between

between

(Average File Size)

10 KB -

3 KB -

 

 

100 KB

33 KB

 

 

 

 

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-V26Uonly)

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-V26Usends out 2 audio streams and receives 1 audio stream, data volume will be as follows.

64 kbps x 3 = 192 kbps

24