Education | AV Distribution Tutorial Accessory and Remote Control Hardware N etwork switches Applications such as network imaging, multimedia production, and digital signage are very demanding. They generate huge data files that often must be transferred between stations based on strict timing requirements. If such traffic is not transmitted efficiently, you end up with jerky video, on-screen graphics that take forever to load, or other problems. These problems arise because in traditional LANs, only one network node transmits data at a time while all other stations listen. This works in conventional, server-based LANs where multiple stations share files or applications housed on a central server. But if a network has high-bandwidth applications, the one-station-at-a-time model just doesn’t work. This is where the value of a switch comes in. Network switches provide clear paths from each workstation (or other source) to its destination on demand. If your AV distribution system uses IP-based technology to multicast video content over a LAN, a network switch absolutely necessary. And not just any network switch will do. Multicasting is transmitting data from one network device to multiple devices. When multicasting with ordinary Layer 2 switches, all attached devices receive the packets, whether they want them or not. Because a multicast header does NOT have a destination IP address, an average network switch will not know what to do with it. So the switch sends the packet out to every network port on all attached devices. This extra traffic can slow down a network. Switches with IGMP support, however, “know” who wants to receive the multicast packet and who doesn’t. When a receiving device wants to tap into a multicast stream, it responds to the multicast broadcast with an IGMP request, the equivalent of saying, “I want to connect to this stream.” Therefore, for multicasting, use routers or switches that support the IGMP protocol. Without this support, your devices will be receiving so many multicasting packets, they will not be able to communicate with other devices using different protocols, such as FTP. Plus, a feature-rich, IGMPsupported switch gives you the bandwidth control needed to send video from multiple sources over a LAN. Specialty KVM extenders Your AV distribution application may require more than components that extend, split, and switch video. You may also need support for workstation control so users in remote offices can access servers or other computer sources hosted elsewhere. For this support, a KVM extender can give you the level of control you need. They enable you to place CPUs in cleaner or more secure locations other than your workspace. Plus they extend switching anywhere from a few meters (over CATx cabling) to up to a few kilometers (over single-mode fiber). Connect the transmitter (local unit) to a CPU or server and have a KVM console (receiver or remote unit) with a VGA or DVI monitor, keyboard, and mouse in another room or office. Many also support multiuser access, making it easy for multiple users to collaborate in a multimedia workflow. CPU with Dual-Head DVI-I Video, Audio, and USB Two DVI-I Monitors and Speakers USB Keyboard and Mouse Remote management/peripheral sharing components These more sophisticated components enable you and other users to access your media servers from anywhere in the world via an IP network—often at the BIOS level, even when the operating system is down. Technically classified as KVM extenders, they’re ideal for use where you need to precisely access and control isolated, standalone servers, such as in remote digital displays. And for a digital signage network, all you need is an IP network in the installation to easily deliver content from one playout device via a digital DVI video link. The latest models support high-quality video, too. This can be a single video head, or dual- or quad-head computers. Because video is transferred digitally, you can count on high color and picture fidelity at LAN speeds. Standard CATx cabling delivers IP traffic up to 100 meters, or you can use fiber cable to go farther, over miles, using Ethernet switches or media converters. No-loss compression minimizes bandwidth. What’s nice is, these extension and sharing devices can also extend not just video and keyboard/mouse signals, but they often also provide easy access to external peripherals. In addition to keyboard/mouse emulation, they support emulation for standard Human Interface Devices (HIDs), such as touchscreens. Dual-Monitor DVI Extension over IP IP Network Dual-Head Transmitter Dual-Head Receiver 12 Tech Support 030 - 241 77 99 | Sales 030 - 241 77 77 | On-Site Services 030 - 241 77 44
Distribution Components Security, Optimization, and Troubleshooting F irewalls/data security equipment To ensure data privacy, work with your IT department to implement protection and safeguard your content. This is particularly important if you’re using your AV distribution system to send video across a hospital or government network and if you have to comply with HIPAA, HITECH, PCI, or other data-protection standards This may require establishing IPsec VPN tunnels between sites. Newer technologies, however, enable you to establish an instant encrypted connection between locations without the administrative hassle of setting up a separate tunnel for each link. What’s more, these technologies don’t add latency, which can bog down your video and data communications. Skew compensators Some video extenders are not designed to transmit video across cable that’s higher than CAT5. In fact, with these extenders, the higher-grade cable may actually degrade video. The problem is with the cable twists of CAT5e and CAT6 cables; the wire distance that a signal has to travel is different for each pair. This doesn’t normally cause a problem with data, but if you’re sending higher-resolution VGA analog video signals across long cables, you may see color separation caused by the signals arriving at different times. If the extender you’re using doesn’t have built-in skew compensation, the remedy is a device that compensates for skew. (NOTE: This applies only to VGA analog signals and not to digital HDMI and DVI signals.) Pattern generators Use these to ensure video signal reproduction and display are up to par in your AV and digital signage applications. They enable you to generate test patterns to troubleshoot video calibration issues. Pattern generators are particularly useful for testing in applications where accurate video reproduction is important, such as healthcare, biotech, educational, and industrial settings. Cable testers In addition to pattern generators, you can ensure a quality video infrastructure by troubleshooting supporting cable runs. With one of these handheld testers, you can spot slow cables, bad connectors, incorrect wiring, improper lengths, and low signal levels from switches, PCs, and other hardware in your AV network. If you have a qualification tester, you can also test for available bandwidth and distinguish between network and cable problems. For more troubleshooting products, go to www.blackbox.nl 5 common video errors and how to fix them. Digital HDMI and DVI formats provide sharp, crystal-clear image quality. However, problems can occur. Here are the five most common: Problem 1: Black screen (no picture at all). Possible cause: A. Bad cable or cable that’s too long, causing either the video signals or EDID/HDCP control signals not to be transmitted properly. Make sure that you use quality, high-speed HDMI® cables—they don’t even have to be expensive ones—or try an HDMI extender. B. HDCP is unsupported. Does the display support HDCP? DVI displays usually don’t. Problem 2: “Sparkles” in the picture. Usually caused by: HDMI cable that’s too long or of inferior grade. The solution is to use a video extender, and/or buy quality HDMI cables from a reputable supplier. Problem 3: RGB color tint. Usually caused by: A color encoding issue, a common problem when using a DVI display with an HDMI source. If you’re using a splitter or an extender between your source and the link, make sure it handles EDID. If possible, force the source (for instance, a Blu-ray player) to output HDMI video with RGB color encoding instead of Component (YPbCr) video encoding. Problem 4: White noise or “snow” on-screen. Usually caused by: An HDCP issue. This is actually what the encrypted video looks like. It happens when your display (or any active component, like an extender, used in the transmission) doesn’t support HDCP. The display, in turn, isn’t able to decrypt the video stream. Be sure to use equipment that supports HDCP. Problem 5: Flickering or unstable image. Can be caused by: Electromagnetic or radio frequency interference, bad cable, or cable that’s too long. These all can cause issues with HDCP or the signal, resulting in flickering or the video randomly disappearing then reappearing after a second. The solution: Use certified high-speed HDMI cables instead of standard HDMI cables, or if you need to go long distances, try an extender. If you’re already using an extender, try changing to shielded CAT6 solid-core bulk cable. For more information and our online store, visit www.blackbox.nl 13
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