The HDMI specification does not define a maximum cable length. As with all cables, signal attenuation becomes too high at a certain length. Instead, HDMI specifies a minimum performance standard. Any cable meeting that specification is compliant. Different construction quality and materials will enable cables of different lengths. In addition, higher performance requirements must be met to support video formats with higher resolutions and/or frame rates than the standard HDTV formats.
The signal attenuation and intersymbol interference caused by the cables can be compensated by using Adaptive Equalization.
HDMI 1.3 defined two categories of cables: Category 1 (standard or HDTV) and Category 2 (high-speed or greater than HDTV) to reduce the confusion about which cables support which video formats. Using 28 AWG, a cable of about 5 meters (~16 feet) can be manufactured easily and inexpensively to Category 1 specifications. Higher-quality construction (24 AWG, tighter construction tolerances, etc.) can reach lengths of 12 to 15 meters. In addition, active cables (fiber optic or dual Cat-5 cables instead of standard copper) can be used to extend HDMI to 100 meters or more. Some companies also offer amplifiers, equalizers and repeaters that can string several standard (non-active) HDMI cables together.