Tips for Combating HDMI Power Management Issues
Plus, learn the benefits of using AOC HDMI in commercial applications
Since its inception in 2002, HDMI (High-Definition Multimedia Interface) has been the industry standard interface for transmitting high-quality audio and video.
Recognized with a Technology and Engineering Emmy Award from the National Academy of Television Arts and Sciences in 2009, HDMI continues to be a crucial component for commercial integrators connecting AV sources - such as satellite TV, cable boxes, and media servers - to displays.
Yet, as HDMI technology evolves to support higher resolutions and longer distances, integrators face increasing challenges, particularly with HDMI power management. Specifically, issues transpire when integrators use Active Optical Cable (AOC) HDMI, which is capable of handling higher resolutions signals across far distances. The problem? These cables have higher power requirements that cannot be met without an additional power source.
For those who may not be clear on AOC HDMI adoption and the benefits of using this newer form of cable in commercial applications, let's review the features and benefits - as well as the ways AOC HDMI can help address power management issues.
Active Optical Cable HDMI (AOC HDMI) is a newer type of HDMI cable that relies on fiber optics rather than copper. Fiber optic enables longer cable runs and more bandwidth, which means it can be used in commercial applications where the source device may not be near the screen. “The data rate went up and the resolution went up, and so did the need [to accommodate] longer distances,” says Jeffrey Boccaccio, president of DPL Labs.
“In the CI environment, you're going to have to go a lot further than 30 or 35 feet, the maximum for [earlier versions of] HDMI. And there are so many variables: What kind of distance do we need to go? What kind of resolution do we need to get? And what kind of processing do we need?” says Jason Harbst, technical sales support/project registration supervisor at ADI Global Distribution.
By running signals through fiber optics rather than copper, AOC HDMI can achieve higher resolutions across longer distances. The end-to-end connection interface is the same, maintaining the HDMI protocol. The only exception, according to an HDMI.org article on the specs of powered 2.1 HDMI, is that powered AOC HDMI is not omnidirectional.
“Connection is the same as attaching an ordinary, 'wired' HDMI Cable, except that active cables can only be attached in one direction: One end of the cable is specifically labeled for attachment to the HDMI Source (transmitting) device, and the other end of the cable must be attached to the HDMI Sink (receiving) device. If the cable is attached in reverse, no damage will occur, but the connection will not work,” HDMI.org indicates.
When higher resolutions like 2K, 4K and now 8K first reached the mainstream, they were primarily adopted in consumers' homes. “On the commercial side, a lot of [customers] are still at 2K and don't really have any need to go into a 4K resolution,” Boccaccio says. “They're looking for digital signage, or they have an audience that's looking for content, but not necessarily the highest quality.”
However, as 4K becomes more prevalent and 8K emerges to become common - if not the standard - in homes, expectations will rise for 4K in sports bars, corporate boardrooms, education facilities and other commercial applications.
While AOC cables address many of the challenges of distributing ultra-high-resolution signals across long distances, it leaves integrators with one significant problem - the technology has yet to overcome power management.
Boccaccio explains, “Inside a cable are 19 pins, or wires. Out of the 19, they use eight of them just for video. Then, they use one for hot point and one for power. The power wire is required to carry a certain amount of current, which is 50ma. This is the standard in the industry. That's very small. You could maybe run an LED with it, but you can't run a receiver, AVR or TV set. It doesn't have the strength to do that. It wasn't designed for that.”
This can result in device failures, overheating and signal degradation if power requirements aren't managed carefully.
While AOC HDMI addresses many of the challenges of higher resolutions across longer cable runs, it can leave systems short of the power they need to run - and in the long-term, power-stressed devices may fail from overheating. “It may fail an hour later; it may fail a year later,” Boccaccio points out. It's not difficult to diagnose, however, because the symptoms are clear. It won't be a slight diminishment of picture quality, visible only to the most discerning viewers. Rather, Boccaccio says, “It's going to be a picture that's blinking out all the time, highly distorted or dead.”
As the electronic components begin to fail because voltage declines, the result might be a snowy picture or a picture that blinks out occasionally. In the short term, turning off the system and allowing it to cool down can help. Ultimately, however, the system will fail. As the regulator gets warmer, it will, at some point, shut off.
“We have a source, a Satellite TV or Blu-ray player, and it's putting out some voltage. You have an integrator who plugs in an AOC cable, and it works. But he doesn't know that the AOC he is pulling may require 100mA or 120mA to operate. The source will try to satisfy that 120mA, even though it's only got maybe 60mA or 70mA in it. There's a regulator inside each source. These regulators send this voltage out and, as they regulate, they get warm. They have to dispense the energy somewhere,” Boccaccio says.
Boccaccio and Harbst share four ways to address HDMI power management concerns. Keep reading as we explore each below.
According to Boccaccio, devices connected through HDMI should have enough power headroom to support the higher current demands of AOC HDMI cables. Problems occur when certain system source components don't pull their weight. If one component doesn't provide enough power, other devices will suffer, as well.
“The bottom line is headroom - the more headroom any device can contribute, the less likely these problems will exist,” Boccaccio writes in CE Pro. It's important to note that these problems also exist in commercial integrations and are often compounded by longer cable runs or prolonged usage, which can cause components to overheat faster. Integrators should verify that source devices can meet the power requirements to prevent these issues down the line.
In applications requiring cable runs longer than 100 feet or so, Harbst mentions you can use power extenders that rely on Cat-6 or Cat-6a cable to ensure sufficient voltage across distances. These extenders have their own power requirements on top of the 5 volts required for HDMI. You'll need a plug-in transformer on the transmitting or receiving end. “You want to boost up enough power to be able to power those devices plus let the feed go through the HDMI itself,” he says.
One of the issues Boccaccio mentions is that many AOC HDMI products don't meet HDMI power current specifications. HDMI sources are designed to generate 5-volt DC with at least 50ma of current, as Boccaccio points out. In lab testing, DPL Laboratories discovered that AOC power consumption caused interoperability issues in the field.
Source products can provide additional power to the system. But it's important to find compatible products that meet or exceed certification requirements. “Remember, under HDMI limits, every source must supply at least 50mA to earn certification,” Boccaccio writes in CE Pro. Choosing products that have been shown to meet expectations and components that show they are certified to work together can help minimize power problems.
Running HDMI over IP, or media over IP, can help overcome power challenges, Harbst says. “When we're speaking of extenders, one of the things we should consider is HDMI over IP, or even media over IP,” ADI says. “You're pretty much unlimited in what you can do with that in terms of how many sources and displays. Everything goes over the network.”
This alternative, of course, requires more networking knowledge and more extensive equipment than a basic network switch. “If you're doing HDMI over IP, you're going to have an encoder, which will take your HDMI source and convert it to a category cable that will go into a network switch,” Harbst explains. “Then, you come out of the network switch, and you're going to send that [signal] to a receiver located near the display, and It's just going to convert back to HDMI.”
Using Power over Ethernet (PoE) for devices like encoders and receivers, HDMI over IP effectively bypasses the power limitations of conventional HDMI cables. “They'll just get the power right off the switch,” Harbst says. He adds that there are other benefits to HDMI over IP, such as greater video management capabilities. “It opens integrators up to a much greater world of possibilities.”
As HDMI resolutions continue to advance, HDMI power management will remain a critical concern for commercial integrators. By selecting certified products, considering HDMI over IP and ensuring power headroom, professionals can mitigate common HDMI power issues and deliver optimal AV performance.
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