The transition to HDMI 2.0 was overwhelmingly driven by the urge to support higher resolution signals, notably 4K HDR 4:4:4 with a 600-megapixel flow rate. HDMI 2.0 is furthermore built to accommodate the carriage of 8K signals which, while still some years away, will eventually become an important part of the AV ecosystem. In the meantime, the industry eagerly awaits what HDMI 2.1 and future specs will offer for visual quality benefits.
Surprisingly, many cables on the market today are still limited to 1080p and 4K 4:2:0. On a short transmissions, the viewer might still receive and see a 4K image using these connections. In any scenario, a quick 10-to-20 second test will generally help determine the capabilities to carry HDMI 2.0/1.4/1.2 signals over each connection. The kind of tests you run will make a big difference as to how quickly the problems are solved, if at all.
There are a number of testing options on the market today, though many fall short when it comes to HDMI testing. Most HDMI testers focus on pattern testing versus physical layer testing. These pattern-oriented devices understand how to read a video stream, and run through a loop with the HDMI cable from transmission to receipt. These provide an appropriate comparison of the pixel levels through the loop, and confirm that the cables can carry HDMI 2.0, for example.
This provides value to a degree, but there are additional physical layers in the mix that can adversely affect signal integrity. The wiring inside the HDMI cable can have a remarkable influence. In the short term, the video activated and transmitted through the cable will work fine, and the image will appear exact, even if there is damage on or underneath the shielding.
Testing the cable itself will identify these more advanced issues. For example, one increasingly common problem is the reduction of shielded wire from within the cable. HDMI cables have 18 standard conductors for video, audio, Ethernet, and data moving over twisted pairs of wiring inside. Each of these wires should be shielded to maximize performance, which represents a 19th conductor.
Testing with a pattern generator will provide return information that suggest all 19 conductors are functioning properly. For short cable runs, this may happen even if there are issues with some of the conductors. The problems visibly surface on longer cable runs, and/or if there is a continuous signal moving through shorter cables for hours. For example, a 24/7-hour system with internal conductor shortcomings will gradually leak outside the wiring. This will inevitably cause signal degradation and ultimately affect performance.
There is no question that testing with an HDMI pattern generator will affect the overall depth and integrity of test. HDMI transmitters and receivers use equalization for error correction to improve the HDMI transmission. Not all the HDMI transmitters/receivers use the same equalization, which means that testing high-bandwidth HDMI signals with a pattern generator will often hide issues caused by the cable’s physical layer and associated wiring quality.
This can feel like a complicated situation for tech managers that have no way to reliably troubleshoot the connections. Perhaps the integrator installed the system and verified integrity through a pattern generator, and everything checked out.
Then, perhaps, the system remained dormant over a holiday week or between semesters after the integrator left the job site. The moment the system was turned on with the goal of passing 18Gpbs, the video drops surfaced. There is no HDBaseT extension—just a 3-foot cable connecting the source and sync devices. The HDMI cable simply cannot carry the high-bandwidth content between the two points.
There is also the issue of overuse. Consider a meeting space where user after user is connecting to an HDMI cable. Most HDMI cables can accommodate up to 500 connections and disconnections, but the possibility of earlier damage certainly exists to do a more consistent flow of different users. Today’s more diverse, portable test devices will help installers verify signal presence and integrity through a variety of key parameters, including activation of links to transmit through the cable, even without a source or sink to receive the signal; the quality of transmission on the uplink (much higher bandwidth) and downlink; and improper terminations or crimps that cause faults through the twisted pair wires.
These and other problems can be identified and fixed on the spot, without the need to bring in a 4K display or projectors to confirm and evaluate the link. Special HDMI test modules are emerging to connect the tester directly to the wire, and return detailed physical layer readings to the handheld or a connected laptop. This allows the tech manager to immediately confirm whether the HDMI cable can reliably carry high-bandwidth signals over the long term by performing tests that transmit the video, verify terminations, and verify cable quality.
Attaching a professional HDMI module to both ends of the cable will provide instant access to crucial cable-quality data, including the presence of each of the 19 HDMI-standard conductors, with instant feedback on missing or defective wiring (called an HDMI Swipe Test); HDMI bandwidth requirements for signal carriage (called an HDMI compatibility test); confirmation if any of the cable’s conductors are shorted or missing; and gauge (AWG) measurements for each of the conductors.
A final important consideration is certification. This is something that tech managers cannot achieve with a common network analyzer, for example. Devices that can immediately offer a report that displays the minimum and maximum parameters, provide details on signal degradation and improvement, and what artifacts influenced the transmission provide major benefits to everyone involved.
Manufacturers’ warranties are further protected through a certification report that verifies the performance of their equipment. Furthermore, if problems arise several months down the road, comparisons of the initial certification can be made with the current measurements to isolate problems and failures. For example, if someone ran electrical wiring for an air conditioner next to the AV system, that can be isolated as an outside interference problem.
The ability to accurately and thoroughly test each cable’s quality and performance is paramount to long-term viability of a new AV system. Using a modern HDMI test device will better assure the end user that their system can move high-quality, high-resolution signals with maximum integrity, while having better insight into a broader array of testing parameters.
Ariel Marcus is co-founder and chief technology officer at MSolutions.