Digital television

Old TVs used analog signals. New TVs use digital signals instead. These new signals make the picture very clear. They also make the screen look wide. This is called high definition.

Digital signals can send many channels at once. This uses less space for the signals. You can watch many shows on one channel. It is a big change for TV. Do you have a wide TV?

Digital television is a new way to send TV signals. Old TVs used analog signals. Digital TV uses digital encoding instead. This change makes pictures look very clear. This clear picture is called high-definition television, or HDTV.

HDTV screens are often wide. They use a 16:9 aspect ratio. Old analog TVs used a narrower 4:3 shape.

Digital TV is also very smart with space. It uses radio spectrum, which is the space used for signals. One digital channel can send up to seven channels at once. This is called multicasting. Broadcasters can choose to send one big HDTV signal. Or, they can send many smaller signals.

People get these signals in different ways. Some use an antenna to get digital terrestrial television. This is also called DTT. Others use digital cable or satellite. Some people even watch TV over the internet. This is called IPTV. Different parts of the world use different rules for these signals. For example, the US uses the ATSC standard. Many other countries use the DVB standard.

Digital television, or DTV, is a modern way to send TV signals. It uses digital encoding to carry information. This is different from the older analog technology. Digital TV is a huge step forward for how we watch shows. It allows for high-definition television, which people call HDTV. These pictures have much more detail than old analog images. Most HDTV screens use a wide 16:9 shape. This is wider than the narrow 4:3 shape used by old TVs.

This technology works by using space very wisely. Signals travel through something called radio spectrum. This is a limited amount of space for signals. Digital TV can fit many channels into a small area. It can send up to seven channels in the same space as one old analog channel. This is often called multicasting. A broadcaster can choose to send one high-quality HDTV signal. Or, they can send many smaller signals at once. This helps them use their bit budget effectively.

The history of digital TV began in the 1980s. Companies like Toshiba made some of the first digital TVs. These sets used tiny computer chips to change analog signals into digital ones. Sony and NEC also announced digital sets in 1986. At that time, true digital broadcasts did not exist yet. In 1990, a company called General Instrument showed that digital signals could work. This helped the FCC decide to create new rules for digital TV. They wanted the new signals to be much clearer than old ones.

Different parts of the world use different rules, or standards. In the United States, Canada, and Mexico, people use the ATSC standard. This uses a method called 8VSB for signals on the ground. Many countries in Europe, Africa, and Asia use the DVB standard. Japan and the Philippines use a system called ISDB. This system works well for both home TVs and mobile phones. China uses a standard called DTMB. In South Korea, a technology called DMB sends TV to phones and laptops. Each of these systems helps people watch TV in their own way.

You can receive digital signals in many different ways. Some people use an antenna to get digital terrestrial television, or DTT. Others get their shows through digital cable or satellite. You might even watch TV over the internet. This is called IPTV. Some special systems even let you watch TV on a cell phone. This is like how you might use a phone to look at a map or listen to music. Digital TV connects the world of broadcasting to the world of computers.

Digital television, or DTV, is a method of transmitting television signals using digital encoding. This technology represents a major shift from the older analog systems that used continuous signals. DTV is significant because it allows for High-Definition Television, or HDTV. These signals provide much greater resolution than previous analog formats. Most digital broadcasts use a widescreen aspect ratio of 16:9. This is wider than the traditional 4:3 ratio used by analog sets. By using digital encoding, broadcasters can use the radio spectrum more efficiently. They can transmit up to seven channels within the same bandwidth required by a single analog channel.

The mechanism of digital television relies on how data is compressed and sent. In the 1990s, the availability of inexpensive, high-performance computers changed everything. Previously, uncompressed video required massive amounts of bandwidth. A standard-definition signal (SDTV) needed significant space, while HDTV required even more. To solve this, engineers used motion-compensated DCT video compression formats, such as MPEG. This allows the video to be broken down into digital data that fits into smaller spaces. Broadcasters can then use a technique called multicasting. They can distribute their "bit budget" by sending one high-quality HDTV feed or several lower-resolution SDTV feeds simultaneously. This is often managed automatically by a statistical multiplexer.

Different regions of the world have adopted different broadcasting standards. One major standard is Digital Video Broadcasting, or DVB. It uses coded orthogonal frequency-division multiplexing (OFDM) modulation and supports hierarchical transmission. DVB is used in approximately 60 countries across Europe, Africa, Asia, and Australasia. In North America, the Advanced Television System Committee (ATSC) standard is common. This uses eight-level vestigial sideband (8VSB) for terrestrial broadcasting. It is used in nine countries, including the United States, Canada, and Mexico.

Another system is Integrated Services Digital Broadcasting (ISDB), used in Japan and the Philippines. ISDB is designed to work for both fixed home receivers and mobile devices. It can support up to three layers of hierarchical transmission using MPEG-2 video and Advanced Audio Coding.

Other specialized standards exist to serve specific needs and locations. The ISDB-T International standard is an adaptation used in most of South America, as well as Botswana and Angola. It utilizes H.264/MPEG-4 AVC technology. In China, the Digital Terrestrial Multimedia Broadcast (DTMB) standard is used. This employs time-domain synchronous (TDS) OFDM technology. South Korea developed Digital Multimedia Broadcasting (DMB) specifically for mobile devices. This allows multimedia like TV and radio to be sent to phones, laptops, and GPS systems. There is also a special form of ISDB called 1seg. In this version, a channel is divided into 13 segments. Twelve segments are for HDTV, while one is for narrow-band receivers like cell phones.

The history of digital television began with early experiments in the 1980s. In the mid-1980s, Toshiba released one of the first TVs with digital capabilities. These sets used microprocessors to convert analog signals into digital video. This allowed users to freeze pictures or view two channels at once. Sony and NEC also announced digital-capable sets in 1986. However, true digital broadcasts were not yet available. In 1990, the American company General Instrument demonstrated that a digital signal was feasible. This led the FCC to demand that new standards provide at least twice the resolution of existing analog images. It also required that new signals be able to be simulcast with NTSC signals so viewers would not lose service.

A major technical debate occurred regarding how images are scanned. This involved a dispute between the consumer electronics industry and the computer industry. The computer industry favored progressive scanning, which scans lines in a continuous sequence from top to bottom. They argued it prevented flickering and worked better with the Internet. The electronics industry and broadcasters preferred interlaced scanning. This method scans even-numbered lines first, then odd-numbered lines. Broadcasters argued interlaced scanning was necessary to transmit the highest possible quality. At the time, they wanted to reach 1,080 lines per picture and 1,920 pixels per line. This debate shaped how different industries connected their technologies.

Today, there are many ways to receive digital television signals. Digital terrestrial television (DTT) uses an antenna or aerial to catch signals from local transmitters. Digital cable and digital satellite are other common delivery methods. Some countries use digital multichannel multipoint distribution service via microwaves. For mobile users, standards like DVB-H or DMB allow for handheld reception. There is also Internet Protocol television, known as IPTV, which delivers content over computer networks. Each of these methods uses the core principles of digital encoding to bring high-quality media to different types of devices and locations.