When tackling a commercial HDMI A/V system with some HDCP mixed in, it’s best for installers to first take a deep breath.
Sources and displays with HDMI and HDCP – the new four letter words of A/V – were not designed for commercial installations. But with a little knowledge and planning, you can design and install profitable, reliable systems. Here are some tips.
1. Check HDCP compatibility of any DVI devices you will be using in the system. The HDMI standard calls for HDCP implementation. DVI does not. Know if you DVI devices are HDCP capable or not.
2. Remember that once a signal has HDCP, it must always have HDCP. If you are incorporating HDCP sources, you cannot convert the signals or use a device that blocks the HDCP information along the way. Any distribution amplifiers, switchers or other products you need to incorporate to meet the signal routing requirements must pass the HDCP if HDCP is to be used.
3. Other than sources and displays, all devices used should provide re-clocking and equalization of HDMI signal. Everything that is used in the middle of the signal path – distribution amplifiers, A/V receivers, etc. – should have active re-clocking and equalization circuitry to rebuild the signal. Avoid passive devices.
4. An HDMI 1.3 device does not necessarily support all the features of the HDMI 1.3 specification, so check each device specified and installed for the precise features required in that system. For example, a product might claim HDMI 1.3 on the packaging and provide deep color compatibility but not HD Audio. Don’t just look for the version number; be sure you have the features you need for your particular system in every component.
5. The signal driving capability of sources, especially in Blu-ray players, can greatly vary from model to model. Know the limits of each component you specify and install.
If you have two Blu-ray players – even from the same manufacturer – one might be able to drive a 1080p signal 30 feet and another just 20 feet over cable of identical construction. You need to know what each component can do before you specify it and install it or you will be making return trips to the job site for troubleshooting and equipment replacement.
6. Not all HDMI inputs of a display are created equal. HDMI input No. 1 usually is backed by the best electronics. With the same source and the same 50 foot cable, you could conceivably get a picture on HDMI input No. 1 of a display and not on HDMI input No. 3. This is a probably a cost-savings technique by display manufacturers who are assuming that most applications of their product will be with a short cable connected directly from the source to the display.
7. Know what EDID your source is seeing and when it sees it. This will determine what kind of signal your source will send out. EDID is 256 bytes of data that a display sends to a source to identify all its capabilities, especially its native resolution.
Be sure that you can pass that EDID information from the monitor to the source. If you can’t because of system design, employ an EDID capture and emulation device to ensure the source sees the correct EDID for the display being used. Don’t incorporate any device in your signal path that does not allow EDID to pass unless you have accounted for it with an EDID capture and emulation solution in the system design and installation.
8. If you need to employ range extenders, be careful of range extenders that rely solely on the HDMI source for power. Externally powered devices will provide reliable and repeatable results. There are too many variables with the 5-volt power from the source.
Is it up to the proper level? Is it too low or too high? Does a distribution amplifier or switcher in the system that the signal passes through affect the level? It is simply best to protect your system from potential problems by using range extenders that are externally powered.
9. Signal range will greatly vary based on cable quality, signal resolution, signal color depth and the specific sources and displays used. As bandwidth of the signal increases with greater resolution or color depth, the distance that signal can travel in a particular cable decreases.
Cable construction (quality) can make a huge difference in the distance a signal of a specific resolution and color depth can travel. Even the specific inputs on a display or the outputs of one source versus another can also impact the distance a particular signal can travel. Use the highest quality cables you can, know bandwidth of the signal you are routing and its impact on your system components and design and know your sources and displays.
Don’t leave anything to chance or you will be troubleshooting the job on site and watching your profits disappear.
HDMI is a complex and ever-evolving technology that is at the heart of today’s digital entertainment.
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