digital television

digital television is the transmission of television signals using digital encoding, in contrast to the traditional analog methods. This technology represents a fundamental shift in broadcasting, enabling more efficient use of the radio spectrum and providing higher quality picture and sound. The transition has been a global phenomenon, coordinated by national regulators and international bodies like the International Telecommunication Union.

Overview

The core principle involves converting audio and video into a data stream of bits. Major global standards include ATSC, used primarily in North America and South Korea; DVB, dominant in Europe, Africa, and Asia; and ISDB, adopted in Japan and most of South America. This shift began in earnest in the late 1990s, with pioneering deployments by entities like the BBC in the United Kingdom and Grand Alliance (HDTV) in the United States. The move was driven by the need for spectrum efficiency and to enable new services like high-definition television and, later, 4K resolution broadcasts.

Technical specifications

Video is typically compressed using codecs such as MPEG-2 or the more advanced H.264/MPEG-4 AVC and HEVC. Audio often utilizes Dolby Digital or MPEG-1 Audio Layer II. These signals are then multiplexed into a transport stream via a process defined by the MPEG standards. Key technical parameters include modulation schemes like COFDM for DVB-T and 8VSB for ATSC, which determine robustness against interference. Resolution standards range from Standard-definition television to Ultra-high-definition television, with common formats including 720p and 1080i.

Transmission systems

Signals are broadcast through several primary methods. Terrestrial television uses local transmitter towers, as operated by networks like NBC or public broadcasters such as NHK. Satellite television is delivered via communications satellites from providers like DirecTV and Dish Network. Cable television systems, offered by companies like Comcast and Sky UK, distribute signals through coaxial or fiber-optic networks. Additionally, Internet Protocol television services, such as YouTube TV and Hulu + Live TV, use managed broadband networks for delivery.

Reception and equipment

Viewers require compatible equipment to decode the digital signal. This can be an integrated digital television set or an external set-top box, such as those provided by Roku or Amazon Fire TV. For terrestrial reception, a suitable antenna (radio) is needed, often marketed as a HDTV antenna. Smart TV platforms from manufacturers like Samsung and LG Corporation often include built-in tuners and apps for streaming media. The Consumer Technology Association sets many interoperability standards for this equipment in the United States.

Transition from analog to digital

This process, often called the digital switchover or analog switch-off, involved turning off analog broadcasts to reclaim valuable radio spectrum. The United States completed its transition in 2009 following a mandate by the Federal Communications Commission, which included a subsidy program for converter boxes. The United Kingdom executed a staged switchover concluding in 2012, managed by Digital UK. Other major completions include Japan (2011), Germany (2008), and Australia (2013). This freed spectrum for uses like 4G mobile broadband and public safety networks.

Impact and adoption

The adoption has dramatically improved picture quality, reduced transmission costs for broadcasters like CBS and ITV (TV network), and enabled multichannel television on a single frequency. It facilitated the rise of electronic program guides and interactive services. The cleared spectrum, often auctioned by governments, has been vital for the expansion of wireless services from companies like Verizon Communications and AT&T. Globally, adoption is nearly universal, with final analog shut-offs in countries like Brazil and India occurring in the late 2010s, marking the end of an era defined by NTSC, PAL, and SECAM.

Category:Television technology Category:Broadcasting Category:Digital media