HDMI Corner: Making the Jump to 4K? Here’s How to Stick the Landing

Manufacturers and integrators alike are tripping over themselves trying to ‘make the jump’ to high-speed 4K transmission.

Jeff Boccaccio

Our 4K phone traffic has increased substantially now that higher speed 4K hardware is being shipped. In addition to integrators, many calls are coming from manufacturer’s reps and manufacturers themselves.

They, along with others, are tripping and falling over themselves attempting to “make the jump” to high-speed 4K transmission.

First let’s define “making the jump.” The graphic below says it all. We came from an older HDMI speed of 10.2Gbps and now we are making the jump to 18Gbps. Notice the greater than (>) and less than (<) symbols. This is most important because these cannot change.

Once you cross into 341MHz territory you have to make the jump and stick the landing. This is serious business and it will likely get worse before it gets better.

Look again at the chart — you’re in the red or green. That’s it. You just need to find the hardware that supports this. Good luck.

I knew we were heading toward a car wreck when a well-educated HDMI representative couldn’t wait to show me that his 50-foot 10.2Gbps cable could do high-speed 4K. If people are trying to sell me on this miracle, what are they trying to sell you?

First and foremost, this jump requires more than just speed yet that is what most “experts” seem to be focusing on. There are new rules, changes in the data, new scrambling techniques, content protection and some critical dynamics within the modulated envelope itself that are different. So we will inspect, detect, reject and report on what we find.

A recent evaluation was a 4K Blu-ray player and matching 4K monitor. By using test equipment that can “take control” of the monitor we were able to confirm that the display itself could actually make the jump — impressive, so now let’s take the Blu-ray. Interestingly, upon power up and splash screen the unit produced a 6Gbps Eye. Multiply this by three and you get 18Gbps; its output was too low but that can be dealt with. Remember, though, this is in the perfect world of test and measurement.

“This [move to 4K] requires more than just speed yet that is what most ‘experts’ seem to be focusing on.”​

To simulate a real-world environment we were able to build a special test fixture that could monitor the Blu-ray with a Time Domain Analyzer while running to the display, allowing the equipment to monitor wave form video being transmitted. The unit started OK at 6Gbps but dove to 2.97Gbps once 4K content began. This could be due to the content itself, embedded logic (EDID) in the player or display, or even in the transmission line.

This will be studied further, but you can see how people can be swayed into thinking they have high-speed 4K.

We know that the transmission line can be a bottle neck, and for 4K you must now have a transmission line that can support the entire 18Gbps envelope. Physics controls this to some extent; for instance, you can use a 24AWG cable and if constructed correctly you can squeak out about 20 feet. Beyond that you need extra horse power.

Unfortunately, the only active cable part available today to do this job was designed and built before HDMI Rev 2.0 was even on paper. The part can do 18Gbps but to what level … that wasn’t even published. As long as it is programmed to match what Rev 2.0 calls for, has the additional necessary electronics, and is tested for all three TMDS channels it can, in fact, work.

We find many products hitting the dirt when pushed to 18Gbps, and others that are out of range. At the time this aforementioned part was made nobody knew about: the new dynamics in the video; the new encryption; that the clock proportions were going to change; and the new emission limits set forth under Rev 2.0.

Yes, there are newer products but perhaps not ready for prime time as of this writing. Be careful, unless there are added electronics and special programming to these parts … you may not be “making the jump” when you think you are, and then what happens?