Television

See also History of television.

Television is a telecommunication system for broadcasting and receiving moving pictures and sound over a distance. The term has come to refer to all the aspects of television programming and transmission as well. The word is derived from mixed Latin and Greek roots, meaning "far seeing".

Origins

The origns of what would become today's television system can be traced back at least as far as the scanning disk of Paul Nipkow of 1885. All practical television systems use the fundamental idea of scanning an image to produce a time series signal representation which is then transmitted to a device which reverses the scanning process and which relies on the human eye to integrate the result into a coherent image again. While electromechanical techniques were developed extensively prior to World War II, most notably by John Logie Baird, all-electronic televison systems relied on the inventions of Philo Taylor Farnsworth, Vladimir Zworykin and others to produce a system suitable for mass distribution of television programming. Commercial broadcast programming, starting with experimental broadcasts seen only in a few specially-equipped homes, occurred in both the United States, and the United Kingdom before World War II, but television did not become commonplace in homes until the middle 1950's. While North American over-the-air broadcasting was originally free of direct cost to the consumer and supported primarily by advertising revenue, increasingly television consumers obtain their programming by subscription to cable television systems or direct-to-home satellite transmissions.

Technology

Elements of a television system

The elements of a simple television system are:

An image source - this may be a camera for live pick-up of images or a flying spot scanner for transmission of films
Accompanying this, a source of sound.
A transmitter, which modulates one or more radio signals with both picture and sound information for transmission.
A receiver which recovers the picture and sound signals from the radio broadcast.
A display device, which turns the electrical signals into visible light and audible sound.

Practical telelvision systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification. Transmission may be over the air from land-based transmitters, over metallic or optical cables, or by radio from synchronous [satellite]]s. Digital systems may be inserted anywhere in the chain to provide better image transmission quality, reduction in transmission bandwidth, special effects, or security of transmission from theft by non-subscribers.

Display technology

Thanks to advances in display technology, there are now several kinds of video displays used in modern TV sets:

CRT: The most common are still the traditional direct view CRTs for up to 40in (100cm) (in 4:3) and 46in (115cm) (in 16:9) diagonally. These are still the least expensive, and are a refined technology that can still provide the best overall picture quality. As they do not have a fixed native resolution, in some cases they are also capable of displaying sources with a variety of different resolutions at the best possible image quality.
Rear projection: Most big screen TVs (up to over 100 inch (254 cm)) use projection technology. Three types of projection systems are used in projection TVs: CRT-based, LCD-based, and DLP(reflective micromirror chip)-based. Projection television has been commercially available since the 1970s, but could not match the image sharpness of the CRT; current models are vastly improved, and offer a cost-effective large-screen display. A variation is a TV projector, using the same technology, which can project onto a wall.
Flat panel LCD or plasma: Modern advances have brought flat panels to TV that use active matrix LCD or plasma display technology. Flat panel LCDs and plasma displays are as little as 4in (10cm) thick and can be hung on a wall like a picture or put over a pedestal. Some models can be used as computer monitors too (VGA and DVI or HDMI connections).

Signal connections

The number of ways to connect a video device to a television has increased over the years:

File:High Definition Multimedia Interface Plug.jpg

HDMI - an 19 or 29 pin industry-supported interface plug, that supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. The video part is backward-compatible with DVI.

DVI - a 17 to 29 pin connector that carries digital video signals, designed to carry HDTV but also used in current DVD players and latest digital displays. Copy protection is available using HDCP.

Component video - three separate RCA jacks (colored red, green and blue) carry three video signals, one brightness (luminance) and two colors (chromas), and is usually referred to as "Y, B-Y, R-Y", "Y Cr Cb" (interlaced) or "Y Pr Pb" (progressive), or YUV. Audio is not carried on this cable. This connection provides for picture quality superior to S-Video and is typically used in home theater for DVDs, satellite and analogue HDTV; less common in Europe but is starting to become more widely available.

SCART - a large 21 pin connector that may carry: one video signal composite video; or two video signals S-Video; or for picture quality similar to component video, three signals of separate red, green and blue or RGB; or for best picture quality, four video signals of separate red, green, blue and sync or RGBS; plus right and left line-level audio channels; along with a number of control signals including an aspect-ratio flag (e.g. widescreen). This system has been standard in Europe since mid-1980s for all consumer electronics, which meant that RGBS was available on even the earliest PAL DVD players and satellite receivers. Japan uses a 21 pin RGB connector which is visually similar to SCART but with different pin configurations.

S-Video - small round connector with two separate video signals, one carrying brightness (luminance), the other carrying color (chroma). Also referred to as Y/C video. Provides most of the benefit of component video, with slightly less color fidelity. Use started in the 1980s for S-VHS, Hi-8, and early NTSC DVD players to relay high quality video before component was available. This will sometimes, completely incorrectly, be referred to as an SVHS connector. Audio is not carried on this cable.

Composite video - The most common form of connecting external devices, putting all the video information into one signal. Most televisions provide this option with a yellow RCA jack or occasionally a BNC connector. Audio is not carried on this cable, though two separate cables with similar red and white RCA jacks for right and left line-level audio are commonly bonded to composite video cables.

Coaxial RF - All audio channels and picture components are transmitted through one coaxial cable and modulated on a radio frequency. Most TVs manufactured during the past 15–20 years accept coaxial connection, and the video is typically "tuned" on channel 3 or 4. (or channel 36 in Europe) Audio on these connections is virtually always mono. This is the type of cable usually used for cable television. Most modern DVD players and other video devices no longer modulate RF output, so very old TV sets made before composite video jacks became commonplace will need a modulator. NTSC sets use a 75 ohm F-connector; most PAL sets use a 50 ohm Belling Lee. Most set-top TV antennas have a 300 ohm impedance, so to connect them to a coaxial input requires an inexpensive matching transformer to avoid signal degradation.

300 ohm twin-lead - The predecessor to coaxial cable, generally a flat insulated cable with a pair of wires separated by 0.5 inch, found on NTSC television sets from 1940 to about 1985, and originally used to connect rabbit ears to a receiver. Connection to the set was by connecting the wire to a pair of screws on the back of the television set. Nominal impedance was 300 ohms; connecting an older set to cable or VCRs requires an inexpensive matching transformer to avoid signal degradation due to impedance mismatch. Twin-lead wiring is sensitive to nearby metal objects. Long runs must be properly supported away from metal objects and should be mounted with a loose twist in the cable - see unshielded twisted pair cables which operate by the same principle as properly installed twin-lead.

Aspect ratios

Mechanically scanned television as first demonstrated by John Logie Baird in 1926 used a 7:3 vertical aspect ratio, oriented for the head and shoulders of a single person in close-up.

Most of the early electronic TV systems from the mid-1930s onward shared the same aspect ratio of 4:3 which was chosen to match the Academy Ratio used in cinema films at the time. This ratio was also square enough to be conveniently viewed on round cathode-ray tubes (CRTs), which were all that could be produced given the manufacturing technology of the time. (Today's CRT technology allows the manufacture of much wider tubes, and the flat screen technologies which are becoming steadily more popular have no aspect ratio limitations at all.) The BBC's television service used a more squarish 5:4 ratio from 1936 to 3 April 1950, when it too switched to a 4:3 ratio.

In the 1950s, movie studios moved towards widescreen aspect ratios such as Cinerama in an effort to distance their product from television. Although this was initially just a gimmick, widescreen is still the format of choice today and square aspect ratio movies are rare. Some people argued that widescreen is actually a disadvantage when showing objects that are tall instead of panoramic, others would say that natural vision is more panoramic than tall, and therefore widescreen is easier on the eye.

The switch to digital television systems has been used as an opportunity to change the standard television picture format from the old ratio of 4:3 (approximately 1.33:1) to an aspect ratio of 16:9 (approximately 1.78:1). This enables TV to get closer to the aspect ratio of modern widescreen movies, which range from 1.78:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the better of which uses what is called anamorphic widescreen format. This format is very similar to the technique used to fit a widescreen movie frame inside a 1.33:1 35mm film frame. The image is squashed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PAL-Plus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no image squashing or expanding is used.

Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays, and it remains to be seen whether Work or movie enjoyment will take over. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this will subside as the DVD playback software matures. Furthermore, computer and laptop widescreen displays are in the 16:10 aspect ratio both physically in size and in pixel counts, and not in 16:9 of consumer televisions, leading to further complexity. This was a result of widescreen computer display engineers' uninformed assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls or subtitles, as opposed to viewing content full-screen.

Aspect ratio incompatibility

The television industry changing aspect ratios is not without teething difficulties, and can present a considerable problem.

Displaying a widescreen aspect (rectangular) image on a conventional aspect (square) display can be shown:

in "letterbox" format, with black horizontal bars at the top and bottom
with part of the image being cropped, usually the extreme left and right of the image being cut off (or in "pan and scan", parts selected by an operator)
with the image horizontally compressed

A conventional aspect (square) image on a widescreen aspect (rectangular) display can be shown:

in "pillar box" format, with black vertical bars to the left and right
with upper and lower portions of the image cut off (or in "tilt and scan", parts selected by an operator)
with the image horizontally distorted

A common compromise is to shoot or create material at an aspect ratio of 14:9, and to lose some image at each side for 4:3 presentation, and some image at top and bottom for 16:9 presentation.

Horizontal expansion has advantages in situations in which several people are watching the same set, as it compensates for watching at an oblique angle.

Sound

Television add-ons

Today there are many add-ons for the television set. A few add-ons include Video Game Consoles, VCRs, Cable Boxes, Satellite Boxes, DVD players, or Digital Video Recorders (including personal video recorders, PVRs), the television add-on market is ever growing. Many such devices which are used for programme reception, are known generically as Set Top Boxes.

New developments

Ambilight™
Broadcast flag
CableCARD™
Digital Light Processing (DLP)
Digital Rights Management (DRM)
Digital television (DTV)
Digital Video Recorders
Direct Broadcast Satellite TV (DBS)
DVD
Flicker-free (100Hz or 120Hz, depending on country)
High Definition TV (HDTV)
High-Definition Multimedia Interface (HDMI)
IPTV
Internet television
LCD and Plasma display Flat Screen TV
Pay Per View
Picture-in-picture (PiP)
Video on-demand (VOD)
Ultra High Definition Video (UHDV)
Web TV

Geographical usage

Summary of first countries that introduce TV

Content

Advertising

Since their inception in the USA in 1941, TV commercials have become one of the most effective, most pervasive, and most popular methods of selling products of many sorts, especially consumer goods. U.S. advertising rates are determined primarily by Nielsen ratings.

Programming

Getting TV programming shown to the public can happen in many different ways. After production the next step is to market and deliver the product to whatever markets are open to using it. This typically happens on two levels:

Original Run or First Run - a producer creates a program of one or multiple episodes and shows it on a station or network which has either paid for the production itself or to which a license has been granted by the producers to do the same.
Syndication - this is the terminology rather broadly used to describe secondary programming usages (beyond original run). It includes secondary runs in the country of first issue, but also international usage which may or may not be managed by the originating producer. In many cases other companies, TV stations or individuals are engaged to do the syndication work, in other words to sell the product into the markets they are allowed to sell into by contract from the copyright holders, in most cases the producers.

In most countries, the first wave occurs primarily on free-to-air (FTA) television, while the second wave happens on subscription TV and in other countries. In the U.S. however, the first wave occurs on the FTA networks and subscription services, and the second wave travels via all means of distribution.

First run programming is increasing on subscription services outside the U.S., but few domestically produced programs are syndicated on domestic FTA elsewhere. This practice is increasing however, generally on digital only FTA channels, or with subscriber-only first run material appearing on FTA.

Unlike the U.S., repeat FTA screenings of a FTA network program almost only occur only on that network. Also, affiliates rarely buy or produce non-network programming that isn't intensely local.

Social aspects

Alleged dangers

Paralleling television's growing primacy in family life and society, an increasingly vocal chorus of legislators, scientists and parents are raising objections to the uncritical acceptance of the medium. For example, the Swedish government imposed a total ban on advertising to children under twelve in 1991 (see advertising). In the U.S., the National Institute on Media and the Family (not a government agency) points out that U.S. children watch an average of 25 hours of television per week and features studies showing it interferes with the educational and maturational process.

A February 23 2002 article in Scientific American suggested that compulsive television watching was no different from any other addiction, a finding backed up by reports of withdrawal symptoms among families forced by circumstance to cease watching.

A longitudinal study in New Zealand involving 1000 people (from childhood to 26 years of age) demonstrated that "television viewing in childhood and adolescence is associated with poor educational achievement by 26 years of age". In other words, the more the child watched television, the less likely he or she was to finish school and enroll in a university.

In Iceland, television broadcasting hours were restricted until 1984, with no television programs being broadcast on Thursday, or during the whole of July.

Technology trends

In its infancy, television was an ephemeral medium. Fans of regular shows planned their schedules so that they could be available to watch their shows at their time of broadcast. The term appointment television was coined by marketers to describe this kind of attachment.

The viewership's dependence on schedule lessened with the invention of programmable video recorders, such as the Videocassette recorder and the Digital video recorder. Consumers could watch programs on their own schedule once they were broadcast and recorded. Television service providers also offer video on demand, a set of programs which could be watched at any time.

Both mobile phone networks and the internet are capable of carrying video streams. There is already a fair amount of internet tv, while mobile phone tv is planned to become mainstream, if it can be effectively sold, early in 2006.

Suitability for audience

Almost since the medium's inception there have been charges that some programming is, in one way or another, inappropriate, offensive or indecent.

References

David E. Fisher and Marshall J. Fisher, Tube, the Invention of Television, Counterpoint, Washington D.C. USA, (1996) ISBN 1887178171

External links