Although high-definition television (HDTV) is now nearly ubiquitous in the modern world, bringing HD cable channels into the homes of average residents has taken decades of hard work among several industries, including TV manufacturers, TV networks, content producers and cable companies. According to Nielsen Media Research, in 2011, over two-thirds of U.S. households had HDTVs, but HD service is available in multiple standards and through several types of providers.
Early History of HDTV
The first televisions were produced in the 1920s. These TVs had very poor resolution but were improved to meet early high-definition standards in the 1940s. Of course, the HDTVs back then were monochrome, and the resolution considered to be HD only consisted of 525 horizontal lines with a 4:3 aspect ratio.
In the early 1970s, about 20 years after the introduction of color TVs, work began on digital compression technologies that were essential in the development of modern HDTV systems. An early HDTV was presented to the public for the first time in 1981, and by the 1990’s, the technology had advanced sufficiently for test broadcasts by a consortium of communications companies and electronics specialists, which included AT&T, Philips, Zenith and the Massachusetts Institute of Technology (MIT).
The First HD Broadcasts
The first large-scale field tests of HD broadcasts occurred in 1994 at 199 test sites across the United States, and two years later, WRAL in Raleigh, North Carolina, became the first TV station to broadcast HD programming. In 1998, HDTV was launched by the Advanced Television Systems Committee (ATSC) with a broadcast of the Space Shuttle Discovery.
Even though HD programming was being delivered to the public through the airwaves by network affiliates, HD cable would not premiere until 2003, which was one year after it was broadcast by satellite TV providers. At first, the only HD programming available on cable TV was provided by the large networks, but independent stations and specialty HD stations were offered soon afterwards.
Modern HDTV Systems
Modern HDTVs conform to standards that have been implemented to ease the transition from standard-definition television (SDTV) and to ensure that programming can be enjoyed from any HDTV. The current standard is fully digital, and analog broadcasts in the U.S. are slated to end by 2015.
HDTV programming uses an aspect ratio of 16:9, which is considered the standard for widescreen TV. This makes the viewing experience more theatrical than what was allowed by the older, boxier aspect ratio of 4:3. The resolution of HD cable systems varies but still meets one of three HDTV resolution standards: 720p, 1080i or 1080p.
The lowest standard considered to be high-definition is 720p, which is a resolution of 1280 pixels in each horizontal row and 720 pixels in each vertical column. This standard is still used by the majority of cable providers. The 1080i and 1080p standards each have resolutions of 1,920 pixels by 1,080 pixels. The difference between them is in how the horizontal lines refresh. In 1080p, each line is refreshed simultaneously while odd and even rows alternate with each refresh in 1080i. Of the three standards, 1080p is considered to provide the best picture, but differences between them are not discernible to the human eye when viewed on TVs with screens of 40 inches or less.
One standard for HDTVs that is still under development is the cables used to carry HD signals. The early standard, which is still used by many computer video cards and monitors, is DVI. The type of cable that is most used today is the HDMI cable. This cable has enough available bandwidth to easily support video signals, audio signals, and encryption codes. Even so, many audiophiles prefer to use HDMI cables only for video signals, and they divert audio signals through dedicated audio cables to separate sound systems.
HD Cable Channels
Cable companies now offer a wide array of programming choices for their subscribers. However, an additional technology fee and a higher monthly subscription fee may be required for access to these channels. Those who do not pay the added fees can only view cable channels in standard definition, but they may still receive HD signals from local affiliates through antennas. In addition, HD cable channels can only be accessed from HD-compatible converter boxes. Most subscribers must upgrade their boxes when they order HD service from their cable companies, but this exchange is usually free of charge.
The HD channels offered to subscribers may be available on several tiers. The lowest tier usually provides cable customers with HD channels for the large networks and for a limited number of basic cable stations. The middle tier often adds all of the HD channels for basic cable, and the highest tier may provide HD support for pay channels, such as HBO and Showtime.
Another type of HD cable programming is On Demand. On Demand is a cable TV service that allows subscribers to choose individual programs from a menu. These programs can then be paused, rewound or fast-forwarded like a DVD or VHS tape. At the top tier, subscribers may have access to over 8,000 HD programs at any given time.