DigitaLinx IPEX2001 Manuel d'installation rapide - Page 8
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IPEX2000 Series Quick Install Guide
Gigabit Switch Features
A high quality, managed Level 2 gigabit switch with a high bandwidth backplane should be used in the installation,
preferably with PoE support. The two primary features to look for in the switch are support for multicast and
support for IGMP snooping, which are required technologies for stable video signals.
Be sure to verify the PoE gigabit switch can provide 15.4 watts to each output under full load. Some switches
support 15.4 watts per output but do not have enough available power under full load. For a 24 port switch, it
should be able to provide about 370 watts to the LAN ports (24 x 15.4 = 369.6) plus power for the switch.
Gigabit Switch Size(s)
When calculating the size of switch needed, the following devices need to be considered:
1.
Number of sources
2.
Number of displays
3.
IPEXCB
4.
Wireless access point for iPad app or Windows app (optional)
5.
Hardwire port for Windows app (optional)
If the installation requires 14 sources and 10 displays, a 24 port switch will not have enough ports for the installation,
because there are no open ports for the IPEXCB.
System Bandwidth
30 Mbps should be considered when calculating the bandwidth for the highest quality video setting. This value
covers the maximum quality 30Mbps encoded stream plus packet overhead. Ten 1080p sources using the highest
quality video setting will be using approximately 300 Mbps of effective bandwidth on the backplane.
When configuring the IPEX2001 in the IPEXCB, the encoding method (CBR or VBR) can be changed as well as the
bandwidth of the signal. CBR is Constant Bit Rate. In a CBR h.264 stream, the encoder uses the same amount of
bits for every second of video. If you set the IPEX2001 to CBR at 10 megabits per second, every second of video will
use 10 megabits per second of bandwidth regardless of the content. A still image will use the same bandwidth as
a moving image.
VBR is Variable Bit Rate. In a VBR h.264 stream, the encoder will transmit different bit rates of data depending on
how much information is present or has changed from frame to frame of video, while averaging the stream to the
bandwidth set. If you set the IPEX2001 to VBR at 10 megabits per second, every frame of video will use varying
bandwidth based on how much information has changed from frame to frame. A still image will use less bandwidth
than a moving image.
Gigabit Switch Expansion
Quite often, a switch will not have enough ports for a complete installation. There are two methods to connect
switches together to expand the number of ports: cascading and stacking.
Cascading refers to connecting the copper LAN port from one switch to another. This is a low cost method of
expanding the number of ports, but the bandwidth is limited to the speed of the LAN port, which will become an
issue if there are more than 20 sources.
Stacking refers to connecting the fiber SFP port from one switch to another. This is a slightly more expensive
option, but it does not interfere with the number of LAN ports needed for the installation. The SFP port on modern
switches will often support 10 Gbps, which should be enough bandwidth for approximately 200 sources.
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