The Trouble with HDMI Connectivity

Purelink conquers the challenges of long-distance HDMI transmission

Initially designed for consumer applications, HDMI has quickly found its way into the pro-AV market. In most connectivity networks, a typical signal transmission from source to display occurs from a direct connection using HDMI cables. However, HDMI’s relatively weak signal does not hold up well over long cable runs.

The Challenge

Based on TMDS (Transmission Minimized Differential Signaling), HDMI consists of a summation of harmonically related sine waves.  As the data rate (or bandwidth) of the signal increases, so does the frequency of the sine waves that make up the signal. 

HDMI loses significant strength after a maximum of 10 meters (33ft.), resulting in image distortion, digital noise (sparkles), or even a complete picture drop-out.

Several factors contribute to the challenge of high-speed digital signal transmission, including:

• Attenuation:  As frequencies increase, signal attenuation of the cables increases due to the “skin effect.” Think of this as a blocked water pipe where fluid only passes along its outer edges, less and less as the pipe gets longer. 
• The Skew Factor:  HDMI’s TMDS means that a pair of signals must mirror each other. When one signal has a positive transition, its complement has a negative transition at the same exact moment.  Ideally, these signal pairs maintain precise timing.  Over long distances, imperfect conditions caused by the twists in the copper cable skew the timing and produce errors. 

Using HDMI Extenders 
To maintain strong, effective HDMI transmissions from room to room or building to building, HDMI extenders regenerate, amplify and equalize HDMI signals for error-free transmissions and consistent video and audio quality. 

The PureLink Advantage