A high-definition (HD) channel is a channel provided by over-the-air broadcasters, digital cable and satellite companies that gives the viewer higher picture resolution and signal quality than those of standard television channels, making for a noticeably sharper image.
History
HDTV was being developed in Japan as far back as 1969. The U.S. demonstrated a similar version in 1981, but the process was hampered for years, until the technology could handle the high bandwidth and the manufacturers could agree on one standard. Plus, the costs involved with producing the televisions, along with creating the network needed to transmit and receive the signals, were prohibitive. The first public HD broadcast in the U.S. was in Raleigh, North Carolina, in 1996.
Specifications
Digital compression and the expanded capabilities of high definition allow for pictures to have an aspect ratio (screen size) of 16:9, which is similar to movie screens, as opposed to the 4:3 ratio of standard televisions. HD provides up to 1080 lines of resolution, which is much higher than the 480 lines of standard TV.
Benefits
The increased aspect ratio, enhanced resolution and higher frame rate (frames per second) create a much sharper picture and greater detail than seen before. Also, the digital compression allows for multi-channel stereo surround sound.
Recent Developments
As of 2009, the majority of Americans still have standard definition TV sets, though HDTV is rapidly growing. Therefore, the major cable and satellite providers offer separate standard and HD channels of stations and cable networks that broadcast in HD. The availability and number of those HD channels depend on the cable or satellite provider.
Potential
With the U.S. switching to digital-only broadcasting by June 2009, and the growing popularity and shrinking prices of HD television sets, the time is coming where every channel will be a high-definition channel.
Tags: cable satellite, aspect ratio, high-definition channel