TV Standards in North America

"High definition" is a relative term. Like all forms of video, the concept of HD video originated in the technology and legal standards of the television broadcast industry. A television standard is an industry-wide platform of specifications for generating and interpreting electronic signals so that all systems (broadcast sending/receiving, videorecording/playback) are compatible in a given region. Because these legal rules drive the development of new recording/playback formats and other video equipment, it is important to have a basic understanding of how they function.

The history of HD video stretches to the earliest days of television in the United States. In 1941, the National Television Systems Committee (NTSC) formulated a standard for black-and-white television in North America. Then in 1953 the committee revised its standard for color television. "NTSC Color" was designed to be backwards-compatible with the black-and-white television infrastructure. All TV was broadcast in color; people had to buy color sets in order to see color TV, but they could still watch the transmissions in black and white on their existing sets. This decision made economic sense, but it also meant that most elements of the television formula (including the resolution, scanning method and aspect ratio) would remain the same as in the 1940s.

Both North America and Japan implemented the NTSC Color standard. Around the early 1970s the Japanese state broadcasting company NHK began developing a more efficient transmission system, which had a higher resolution and a wider aspect ratio, and brought this high-definition prototype to the United States for demonstrations in the following decade. In 1982, a group called the Advanced Television Systems Committee (ATSC) formed to create new television standards to replace Color NTSC in North America.

Contending proposals for the future of television came from all corners of the television and electronics industries. In 1996, the ATSC reached a consensus and gained the approval of the Federal Communications Commission (FCC). A major goal of the new ATSC standard was to phase out analog broadcasting over the next decade. Analog broadcasting was discontinued and replaced with all-digital transmission in June 2009.

Today the ATSC standard is officially in place. Unlike NTSC, which mandated only one recipe for video signals, the ATSC makes room for many variations and includes several subcategories. One subcategory is Standard Definition Television (SDTV), the digital equivalent of the original analog NTSC standards. High-definition Television (HDTV) has a new set of digital parameters. Within HDTV, there are many different permutations of variables. For most practical purposes, it is only necessary to get acquainted with the following three types of HD video,

- 720p - 1080i - 1080p

A discussion of the differences between SD and HD video will clarify these types.