High Definition Television (HDTV)

High definition television (HDTV) is a TV broadcast system that proves higher picture resolution (detail and fidelity) than is provided by conventional NTSC and PAL television signals. HDTV signals can be in analog or digital form.

HDTV has been offered in several countries since its introduction in Japan in 1988. The first HDTV receivers in the United States were introduced at the 1998 Winter Consumer Electronics Show in Las Vegas.

HDTV radio broadcast channels can use the same 6 MHz channel bandwidth. However, it must replace the existing NTSC signal with a new high resolution analog or high speed digital radio signal. Initial demonstrations of HDTV required 2 standard television channels. The FCC has finally approved the “Grand Alliance” standard for high-definition television for the United States that only requires one standard television channel to send a HDTV digital channel and supplementary services.

The FCC introduced a new table of digital television channel numbers and RF power level assignments for existing full-power television stations in the United States in April of 1997. The new assignments were designed to give each television station coverage comparable to the station’s existing radio coverage area when they convert to digital transmission.

The change in channel numbers is likely to be a significant challenge for television stations; many stations, especially in Southern California, have a reduced coverage area. This has resulted in the contesting of the new assignments by some television broadcasters. The Association of Maximum Service Telecasters (an association of local television stations) has proposed an alternative table of channel assignments to address the issues of established broadcasters.

The digital technology that allows high-definition television broadcasts in the U.S. can also be used for “multicasting,” that is, transmitting up to five channels of “standard-definition” television programming. Many broadcasters are examining multicasting as an alternative to high-definition television. If the ability to provide more video channels is more desirable than providing high-definition broadcast quality video, HDTV broadcast service and products may be delayed for their entry in the US marketplace.

In July 1996, WRAL in Raleigh, North Carolina became the first United States television station to commence broadcast of high-definition television signals. As of early 1998, more than a dozen stations have licenses for digital transmission, and the number of licenses is increasing every month. HDTV is likely only to be available in the largest markets in the United States for at least the first year the service is provided, so viewers in smaller markets may have to wait many years before they have the opportunity to use digital and/or high-definition television receivers.

The data transmission rate of the HDTV system is 19 Mbps and it uses the motion pictures experts group (MPEG-2) video compression format. To allow for a gradual migration to HDTV service, HDTV transmission will also contain regular programming of standard television on HDTV radio channels. The simulcast transmission will continue for up to 15 years as standard NTSC televisions and transmitting facilities are phased out. Initially, HDTV receivers will have the capability to receive and display regular NTSC broadcasts.