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Are All HDMI Cables The Same?
Introduction: The author Jeff Boccaccio is well known for his passionate and animated lectures at all the main Consumer Electronics & CEDIA trade shows which I have personally attended. Jeff is the President of DPL Labs and advises Consumer Electronics Manufacturers on technical issues associated with things including HDMI.
“Calls for HDMI assistance continue to roll into DPL Labs. Lately, the majority have been audio/video receiver and Cat 5-related. So we investigate these issues.
Consider the receiver situation. As with cables, not all receivers are created equal. Even those that perform well on a test bench tend to make up their own rules in the real world.
So we built a custom test jig that would intentionally increase and decrease the TMDS* video data integrity. With this jig we can look at video thresholds with different products to see how they react under real-world applications.
The results have been quite a bombshell. Without naming brands, we were surprised to find that there are popular receivers that performed fine under carefully controlled lab conditions but, when sending and receiving lower-quality TMDS* video signals, these units just went nuts!
When you factor in a Cat 5 HDMI extender into this situation, the installer is lost. For those who think they can find an issue by selectively removing products in hope of discovering the problem, that technique won’t work in this situation.
It turns out that when the signal integrity begins to decline, the dynamic range of the system shrinks. For example, if you take a typical DVD, connect it to a receiver, and then output the signal to a video display, all will be cool.
However, take that same receiver and connect it to a Blu-ray player at 1080p/60Hz and you either get intermittent operation or total failure. With our custom testing setup, we can clearly see the systemic impact from both high- and low-quality cable products and receivers.
I would have never believed that short cables less than 3 meters can make or break the job, but by being able to change video signal integrity with our test jig, we got a true handle on how these systems respond to different cables and receivers as separate elements of the total system”.
Bottom line: Only use highly rated cables.
January 21, 2010 – By Jeff Boccaccio
*Transition Minimized Differential Signaling