HDMI Cable 1080i vs. 1080pby David Lipscomb
Although most probably can't tell the difference between 1080i and 1080p, this seemingly small issue is relevant when selecting a High Definition Multimedia Interface, or HDMI, cable. Modern HDMI cables come in a variety of speed ratings, which indicate the capabilities of the cable. As home theater technology moves forward at a rapid pace with HDMI at the hub, it's important to pay attention to seemingly minimal differences in the ratings.
Standard-speed HDMI cables are rated for 720p and 1080i resolution. A carryover from the original HDMI specification, standard-speed HDMI is capable of delivering stunning images. However, the consumer electronics industry continually works toward moving resolutions and bit rates upward. High-speed HDMI cables pass 720p and 1080i, but are also designed to easily transmit 1080p and above. Investing in HDMI cables that handle both today's and tomorrow's resolutions and data rates saves money over time, as the need to re-purchase is less likely.
The "i" or "p" at the end of a resolution indicates "interlaced" or "progressive," respectively. This difference is rarely visually apparent, but does matter in terms of how much data the HDMI cable must transmit. Interlaced resolutions alternate even and odd lines on the screen, rapidly combining to form a cohesive image. Progressive resolutions are sent all at once. The implications for an HDMI cable become obvious; 1080p requires twice the bandwidth than 1080i. This is a key reason why 1080p is common in high-speed HDMI cables, but not standard-speed cables.
Confusing the issue further are redundant specifications for HDMI cables. Standard- and high-speed HDMI cables are recognized as 720p/1080i "category 1" and 1080p-compatible "category 2," respectively. Some HDMI packaging may mention the category rating rather than the speed, while packaging of competing products list do the opposite -- and some may list both. Recognize these redundancies when purchasing.
"Future-proofing" in the consumer electronics world is any effort to reduce the need for repeat purchases while chasing technical innovations. In the case of HDMI cables, which are often tucked into walls and ceilings at considerable expense, this is important. Category 2 HDMI cables are rated to 10.2 gigabits per second, five times the speed of category 1 cables. Moving forward, as resolutions increase from 1080p and beyond, having these high-capacity cables already installed will allow you to more easily upgrade to new technologies, instead of wishing you had purchased more robust HDMI infrastructure.