JVC V25U Startup Guide - Page 21
Network Requirements, Estimation of Total Bit Rate, Bit Rate of JPEG Stream - vf
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Network Requirements ● Ensure that there is sufficient network bandwidth for the data volume to be sent out by VN-V25U. 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 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 is determined by the VN-V25U settings, number of clients, and the client's requested number of frames. The total MPEG4 bit rate from VN-V25U 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. Picture Quality Control Method VGA File QVGA File Size Size VFS 1 (High) (Variable File Size) 2 3 80 KB 60 KB 40 KB 27 KB 20 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 Selectable between between 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) Restrictions on the Number of Distributions for VN-V25U The maximum number of distributions for VN-V25U 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 Distribution Maximum Total at maximum number of maximum bit bit rate distributions rate 1 Mbps and 20 below 20 Mbps 5 Mbps and 4 below 20 Mbps 10 Mbps and 2 below 20 Mbps Larger than 1 10 Mbps Maximum configurable value (24 Mbps) 21