What the Heck is a ‘Weak HDMI Signal’?

Learn the lingo and the characteristics of HDMI to help troubleshooters help you.

Jeff Boccaccio
What the Heck is a ‘Weak HDMI Signal’?

Give the experts a little more to go on than, "I have a weak HDMI signal somewhere."

During the recent CASTLE Summit in Coral Springs, Fla., a manufacturer of HDMI products approached me with a technical issue concerning a “weak” HDMI signal.

I understand that some “manufacturers” are really just importers of products from other parts of the world, where it might be challenging to get tech support from the “manufacturers.” This individual fell into that category.

I could tell from the start of the conversation the person was in desperation mode to get out of this serious HDMI bind. I asked him to describe the exact symptoms and to explain what troubleshooting had already been attempted on the system. His frustrations showed as he wiped his forehead and increased his voice level to exclaim, “There’s a weak signal somewhere.” Unfortunately, that’s about as vague as me saying my home address is “Earth.”

Let’s examine what happens when someone relays a technical diagnosis with the word “weak” in the HDMI world.

Weak where? Is it video? Maybe it is supply voltage? Or in the communication protocol? Something can be less weak, more weak, or just plain weaker. The bottom line is that it varies from low to high which is, at least from an integrity standpoint, what we all deal with regarding HDMI performance.

'Just Update the Firmware'?!

First, separate hardware issues from the software issues. How many times have we all heard, “Just update the firmware”? This has been a major problem in many products due to the software interoperability side of the equation. But you must have the hardware in good standing to ensure the software can communicate correctly. You first need to ensure that the building blocks to the interface are well within the requirements before delving into software troubleshooting.

This is exactly why the procedures we use at DPL take all of the integrity issues and compare them to one another. Let’s break down all of the questions that examining “weak” can yield.

Weak video?

  • Weak direct current?
  • Weak bias?
  • Weak in jitter?
  • Weak in leading edge verses trailing edge?
  • Weak in source signaling?
It would sure be helpful if A/V pros could at least learn the key electrical properties and lingo to help tech-support experts diagnose problems with 'weak' HDMI.

Weak in timing?

  • Weak in cable construction?
  • Weak in cable consistency?
  • Weak in source signal timing data?

Weak DDC (display data channel)?

  • Weak direct current?
  • Weak in loading?
  • Weak in capacitance?
  • Weak in pulldown current?
  • Weak in impedance?

Weak DC?

  • Weak in power supply?
  • Weak direct current?
  • Weak caused by loading?

Weak in hotplug?

  • Weak in hotplug DC limits?
  • Weak in hotplug timing?
  • Weak from hotplug loading?

Notice that many of the performance possibilities on that list share some of the same questions. That's how you meticulously the pros tackle troubleshooting. At DPL, we incorporate these questions into our “Argumentative Matrix” test and measurement procedures. It is these electrical values that make all the difference.

We can't expect all (or many) manufacturers and specifiers to diagnose problems with “weak” HDMI, but it would sure be helpful if A/V pros could at least learn the key electrical properties and lingo to help tech-support experts diagnose the problems.

At the end of the day, an integrator needs to make sure the hardware is in good standing, then proceed into software troubleshooting, and emerge with a solid system design.