ATSC tuner - AbsoluteAstronomy.com

An ATSC tuner, often called an ATSC receiver or HDTV tuner is a type of television tuner that allows reception of digital television

Digital television

Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...

(DTV) television channel

Television channel

A television channel is a physical or virtual channel over which a television station or television network is distributed. For example, in North America, "channel 2" refers to the broadcast or cable band of 54 to 60 MHz, with carrier frequencies of 55.25 MHz for NTSC analog video and...

s transmitted by television station

Television station

A television station is a business, organisation or other such as an amateur television operator that transmits content over terrestrial television. A television transmission can be by analog television signals or, more recently, by digital television. Broadcast television systems standards are...

s in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, parts of Central America

Central America

Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

and South Korea

South Korea

The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...

that use ATSC standards. Such tuners may be integrated into a television set

Television set

A television set is a device that combines a tuner, display, and speakers for the purpose of viewing television. Television sets became a popular consumer product after the Second World War, using vacuum tubes and cathode ray tube displays...

, VCR, digital video recorder

Digital video recorder

A digital video recorder , sometimes referred to by the merchandising term personal video recorder , is a consumer electronics device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device...

(DVR), or set-top box

Set-top box

A set-top box or set-top unit is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device.-History:Before the...

that provides audio/video output connectors of various types.

Another type of television tuner is a digital television adapter

Digital television adapter

A digital television adapter , or digital-to-analog converter [set-top box], or commonly known as a converter box, it is a television tuner that receives a digital television transmission, and converts the digital signal into an analog signal that can be received and displayed on an analog...

(DTA) with an analog passthrough

Analog passthrough

Analog passthrough is a feature found on some digital-to-analog television converter boxes. Boxes without analog passthrough only allow digital TV to be viewed on older, analog-only TVs...

Technical overview

The terms "tuner" and "receiver" are used loosely, and it is perhaps more appropriately called an ATSC receiver, with the tuner being part of the receiver (see Metonymy

Metonymy

Metonymy is a figure of speech used in rhetoric in which a thing or concept is not called by its own name, but by the name of something intimately associated with that thing or concept...

). The receiver generates the audio and video (AV) signals needed for television, and performs the following tasks: demodulation

Demodulation

Demodulation is the act of extracting the original information-bearing signal from a modulated carrier wave.A demodulator is an electronic circuit that is used to recover the information content from the modulated carrier wave.These terms are traditionally used in connection with radio receivers,...

, error correction

Error detection and correction

In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels...

, MPEG transport stream demultiplexing

Multiplexing

The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...

, decompression, AV synchronization, and media reformatting to match what is optimal input for one's TV. Examples of media reformatting include: interlace to progressive scan

Progressive scan

Progressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...

or vice versa, picture resolutions, aspect ratio

Aspect ratio (image)

The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. That is, for an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this...

conversions (16:9 to or from 4:3), frame rate

Frame rate

Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...

conversion, even image scaling

Image scaling

In computer graphics, image scaling is the process of resizing a digital image. Scaling is a non-trivial process that involves a trade-off between efficiency, smoothness and sharpness. As the size of an image is increased, so the pixels which comprise the image become increasingly visible, making...

. Zooming is an example of resolution change. It is commonly used to convert a low-resolution picture to a high-resolution display. This lets the user eliminate letterboxing

Letterboxing

Letterboxing is an outdoor hobby that combines elements of orienteering, art, and puzzle solving. Letterboxers hide small, weatherproof boxes in publicly-accessible places and distribute clues to finding the box in printed catalogs, on one of several web sites, or by word of mouth. Individual...

or pillarboxing by stretching or cropping the picture. Some ATSC receivers, mostly those in HDTV TV sets, will stretch automatically, either by detecting black bars, or reading the Active Format Descriptor (AFD).

How an ATSC Tuner Works

An ATSC tuner works by generating audio and video signals that are picked up from over-the-air broadcast television. ATSC tuners provide the following functions: selective tuning, demodulation, transport stream demultiplexing, decompression, error correction, analog-to-digital conversion, AV synchronization and media reformatting to fit the specific type of TV screen optimally.

Selective tuning

Selective tuning is the process by which the radio frequency

Radio frequency

Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

(RF) of the television channel

Television channel

is selected by a receiver from within a band of transmitted

Transmitter

In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...

RF signals. The tuner usually performs the function of frequency-agile selection, along with rejection of unwanted out-of-band signals.

Demodulation

means transforming the signal from the tuner into a usable signal that a TV set can use to produce quality images and sound without further consideration for the frequency at which it was transmitted. It is separation of a standard baseband

Baseband

In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...

signal from the RF carrier that was used to transmit it through the air (or down a coaxial cable or other long-distance medium.) ATSC as implemented in the US uses 8VSB

8VSB

8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM....

modulation, which requires less power to transmit, as opposed to the also proposed COFDM modulatiion (used in European DVB-T

DVB-T

DVB-T is an abbreviation for Digital Video Broadcasting — Terrestrial; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998...

, which is less prone to multipath distortion and therefore better received in mobile installations.

Transport stream

In the US, multiple digital signals are combined and then transmitted from one antenna source to create over the air broadcasts. By the reverse process (demultiplexing), an ATSC receiver first receives the combined MPEG transport stream and then decodes it to display one of its component signals on a TV set. (In principle, more than one signal within the same transport stream could be decoded by one receiver and displayed on multiple TV sets or as picture-in-picture on a single set, with only one Selective Tuning and Demodulation block.)

Decompression

Since digital signals that are broadcast over the air are compressed (packed smaller), once they are received by the ATSC tuner, these compressed packets of digital data are then decompressed

Data compression

In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

(unpacked to their original size). The ATSC system uses lossy compression, so while the decompressed data size is the same as the original compressed data size, the data produced is not exactly the same as the original data fed into the system at the transmitting site, but it is close enough that most people don't notice much degradation in the picture and sound.

Error correction

Error correction is a technology that is used by the ATSC tuner to make sure that any data that is missing can be corrected. For instance, sometimes interference or a poor-quality signal will cause the loss of some data that the ATSC tuner receives. With error correction, the tuner has the ability to perform a number of checks and repair data so that a signal can be viewed on a TV set. Error correction works by adding to the signal before transmission some extra information that can be used upon reception to fill in gaps. Therefore, error correction has the opposite effect of compression—it increases the amount of data to transmit, rather than reducing it like compression does, and it improves the quality and robustness of the signal rather than reducing it. Compression removes redundant (and some non-redundant) data, while error correction adds some redundant data. The reason for using error correction rather than just using less compression and keeping the redundancy that was already there is that error correction systems are specially designed to get the maximum benefit out of a very small amount of redundant data, whereas the natural redundancy of the data doesn't do this job as efficiently, so with error correction the net amount of data needed is still smaller.

There is a subsection in the ATSC standard (ATSC-E) that allows broadcasters to add extra (and variable types) of error correction to their broadcast streams.
This error correction service is not mandatory in the US, nor is it mandatory in Canada.
It is not known how many HDTV receivers support this error correction standard.
For the transmission of HDTV at 720 or 1080, an extra 1% to 3% added error correction codes will help reduce some of ATSC's poorer performance with weak signals under adverse multipath conditions.
Reception is greatly reduced due to EMI in the shortwave to VHF and UHF bandwidth from nearby computers of all sorts [light], portable WiFi and Broadband internet [medium to strong], microwave ovens [burst while activated], cell phones and the towers they communicate with, and even power lines with electronic {00100} transmissions.

AV synchronization

Lip sync

Lip sync, lip-sync, lip-synch is a technical term for matching lip movements with sung or spoken vocals...

is the coordination of audio and video signals being displayed on a digital TV in proper time. AV synchronization ensures that the audio does not lag behind the video that is being displayed on the TV set or vice versa, so that both audio and video are in sync.

Image reformatting

Media reformatting is extremely important because the formatting of images on TV sets differs significantly according to the technology employed. For instance, some televisions have an interlaced picture, whereas others have a progressive-scan picture. Different televisions have a different aspect ratio

Aspect ratio

The aspect ratio of a shape is the ratio of its longer dimension to its shorter dimension. It may be applied to two characteristic dimensions of a three-dimensional shape, such as the ratio of the longest and shortest axis, or for symmetrical objects that are described by just two measurements,...

United States government mandates

The FCC

Federal Communications Commission

The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

has issued the following mandates for devices entering the US:

By July 1, 2005 all televisions with screen sizes over 36 inches (91.4 cm) must include a built-in ATSC DTV tuner

By March 1, 2006 all televisions with screen sizes over 25 inches (63.5 cm) must include a built-in ATSC DTV tuner

By March 1, 2007 all televisions regardless of screen size, and all interface devices that include a tuner (VCR, DVD player/recorder, DVR) must include a built-in ATSC DTV tuner.

It should be noted that devices manufactured before these dates can still be sold without a built-in ATSC DTV tuner; the lack of digital tuners legally must be disclosed to consumers and most name-brand retailers have incurred onerous FCC penalties for non-compliance with these requirements..

The current regulations are specified in the U.S. Code of Federal Regulations

Code of Federal Regulations

The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...

(CFR).

Analog TV broadcast switch-off

In early 2006 the US Deficit Reduction Act of 2005

Deficit Reduction Act of 2005

The Deficit Reduction Act of 2005 is a United States Act of Congress concerning the budget, that became law in 2006.-Legislative history:The Senate's version passed after a tie-breaking vote was cast by Vice President Dick Cheney. The bill passed the chamber with no Democrats and five Republicans...

became law, which calls for full power over-the-air

Terrestrial television

Terrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...

television station

Television station

s to cease their analog broadcasts by February 17, 2009 (this cut-off date had been moved several times previously). On February 11, 2009 the mandatory DTV broadcast date was moved again to June 12, 2009, although stations were allowed to switch earlier. The delay enabled distribution of more coupons for purchase of converter boxes.

Since June 12, 2009, TVs and other equipment with legacy NTSC

NTSC

NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...

tuners are unable to receive over-the-air broadcasts from United States TV stations, unless the broadcast is from a repeater or low-power transmitter. (See LPTV Answers) Canada has a similar analogue TV termination date set to September 1, 2011 (except in some remote northern regions).

It was feared that the US switch-off would cause millions of non-cable- and non-satellite-connected TV sets to "go dark

Dark (broadcasting)

In the broadcasting industry, dark is a term used to describe a radio station or television station that has gone off-the-air for an indefinite period of time, or as defined by the U.S. Federal Communications Commission , a "silent" station...

". Viewers who did not upgrade, either to a television with a digital tuner or a set-top box, ended up losing their only source of television, unless they relied only upon the aforementioned non-full-power broadcasters. A Congressional bill authorized subsidized converter boxes

Set-top box

in a way that allowed viewers to receive the new digital broadcasts on their old TVs. The actual transition proceeded smoothly with about 235,000 people requesting coupons after the June 12, 2009 transition date.

Two $40 coupons were made available per US address nominally from January 1, 2008 through March 31, 2009; each coupon could be used toward the purchase of one approved coupon-eligible converter box

Coupon-eligible converter box

A coupon-eligible converter box was a digital television adapter that met eligibility specifications for subsidy "coupons" from the United States government...

. The coupons expired 90 days after initial mailing and were not renewable. All households were eligible to receive coupons from the initial $990 million allocated, after which an additional $510 million in coupons was to be available to households that rely exclusively on over-the-air television reception. On January 4, 2009 the coupon program reached its $1.34 billion ceiling and any further consumer requests were placed on a waiting list.

Canadian government mandates

In Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, the Canadian Radio-television and Telecommunications Commission (CRTC) has set August 31, 2011 as the date that over-the-air analog TV transmission service will cease in 31 major markets of the country, including all provincial capitals, plus Ottawa (the National Capital), and most other major urban centres.

As of the end of 2008, there were 22 Canadian DTV transmitters

Digital television in Canada

Digital television in Canada is transmitted using the ATSC standards developed for and in use in the United States. Because Canada and the U.S...

on-air and all existing digital transitional television licenses explicitly proscribe as a condition of license, the broadcast of more than fourteen hours a week of programming not already on the analogue service. Unlike in the United States, there is no plan to subsidise ATSC converter purchases and no requirement that newly-imported receivers decode the digital signal. Canadian retailers are also not required to disclose the inability of new equipment to receive DTV. The Canadian market therefore has been flooded with obsolete new NTSC

NTSC

equipment which lawfully cannot be exported to the US. A limited number of ATSC receivers are in Canadian retail stores as high-definition television

High-definition television

High-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD...

(HDTV) receivers. ATSC CECB converter boxes were first carried nationally in October 2008, with chains such as Best Buy

Best Buy

Best Buy Co., Inc. is an American specialty retailer of consumer electronics in the United States, accounting for 19% of the market. It also operates in Mexico, Canada & China. The company's subsidiaries include Geek Squad, CinemaNow, Magnolia Audio Video, Pacific Sales, and, in Canada operates...

and Home Hardware

Home Hardware

Home Hardware is a privately held Canadian home improvement, construction materials, and furniture retailer. Co-founded in 1964 by Walter Hachborn and headquartered in St...

offering limited selection at higher prices than in the US with no government subsidies. ATSC tuners may also be present in a minority of DVD recorder

DVD recorder

A DVD recorder , is an optical disc recorder that uses Optical disc recording technologies to digitally record analog signal or digital signals onto blank writable DVD media...

s, HDTV FTA receiver

FTA Receiver

A free-to-air or FTA Receiver is a satellite television receiver designed to receive unencrypted broadcasts. Modern decoders are typically compliant with the MPEG-2/DVB-S and more recently the MPEG-4/DVB-S2 standard for digital television, while older FTA receivers relied on analog satellite...

s and personal computer

Personal computer

A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

TV tuner card

A TV tuner card is a kind of television tuner that allows television signals to be received by a computer. Most TV tuners also function as video capture cards, allowing them to record television programs onto a hard disk much like the Tivo digital video recorder does.-Variants: The interfaces for...

s. Outside Toronto it is much less likely to be true. Channel reception of United States ATSC into Canada is limited at best to the strongest signals and type of television antenna

Television antenna

A television antenna, or TV aerial, is an antenna specifically designed for the reception of over the air broadcast television signals, which are transmitted at frequencies from about 41 to 250 MHz in the VHF band, and 470 to 960 MHz in the UHF band in different countries...

used. Indoor passive and amplified antennas are more convenient but outdoor equivalents get better fringe reception without as much interference.

Setup and operation

Most ATSC tuners have relatively simple on-screen menus, and automatically bring the user to a setup

Setup

As pertaining to the playing of a single reed woodwind instrument , a setup is the choice in reeds and mouthpieces a person has made. Players will often have several setups of a selection of these reeds and mouthpieces: one for jazz playing, one for legit playing, etc....

screen when turned on for the first time. This allows the user to pick the time zone

Time zone

A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

and daylight-saving time mode (as all stations transmit time in UTC), and bandscan for stations. The scan "listens" on every channel from 2 to 69

North American broadcast television frequencies

The North American broadcast television frequencies are on designated television channels numbered 2 through 69, approximately between 54 and 806 MHz. Traditionally, the frequencies are divided into two sections, the very high frequency band and the ultra high frequency band. The VHF band is...

, and pauses when it detects a digital carrier wave

Carrier wave

In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

. If it is able to decode the station, it reads its PSIP data, and adds its virtual channel

Virtual channel

In telecommunications, a logical channel number , also known as virtual channel, is a channel designation which differs from that of the actual radio channel on which the signal travels....

s to the channel map. If no PSIP is transmitted, the physical channel number is used, and each transport stream is enumerated according to its TSID (converted from hexadecimal

Hexadecimal

In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...

), or starting sequentially at .1, .2, .3, and so forth, depending on the tuner.

Several TV stations are using or have used a temporary channel to send their DTV signals, and upon terminating analog, move their digital transmission either back to their old analog channel, or to a third channel (sometimes the former analog of another local station), chosen in the digital channel election

Digital channel election

A digital channel election was the process by which television stations in the United States chose which physical radio-frequency TV channel they would permanently use after the analog shutdown in 2009. The process was managed and mandated by the Federal Communications Commission for all...

in the U.S. This requires all viewers to re-scan or manually add the new channel and possibly delete the old one. Doing a full re-scan will usually cause other channels to be dropped if they cannot be received at the moment the scan passes their physical channel, so this is typically undesirable, although many ATSC tuners only have this option. Some have an "easy-add" feature which does not delete what is already mapped in memory. Some allow the user to enter the physical channel and an unmapped subchannel, causing the tuner to search the physical channel. Depending on the tuner, this may or may not automatically add the station and its digital subchannel

Digital subchannel

In broadcasting, digital subchannels are a means to transmit more than one independent program at the same time from the same digital radio or digital television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual...

s to the map, and/or to the user's "favorites". This may also leave the old "dead" channel mapping in place, so that there is the new 8.1, dead 8.1, new 8.2, dead 8.2, etc. In most cases, TV stations will not have the actual frequency they are currently using on their website.If the auto scan does not pick up the signal and the tuner has manual frequency scan capability try to get the actual frequency from the station engineer. This may allow one to stay on one frequency (channel) versus "scanning" (moving too quickly through) and allow one to make antenna adjustments while observing only a problematic channel.

Other errors which appear to be in the tuner are actually the result of incorrect data sent by one or more stations, often including missing electronic program guide

Electronic program guide

Electronic program guides and interactive program guides provide users of television, radio, and other media applications with continuously updated menus displaying broadcast programming or scheduling information for current and upcoming programming...

data. Many ATSC tuners will remember EPG info for each station, but only for a few hours after viewing a channel on that station. Some will not remember at all (displaying only the required channel banner), while a very few others will store data for days (although this requires staying tuned to each station for more than a few seconds in order to receive the extended info). DirecTV

DirecTV

DirecTV is an American direct broadcast satellite service provider and broadcaster based in El Segundo, California. Its satellite service, launched on June 17, 1994, transmits digital satellite television and audio to households in the United States, Latin America, and the Anglophone Caribbean. ...

receivers with ATSC tuners can download the guide at any time, while other TiVo

TiVo

TiVo is a digital video recorder developed and marketed by TiVo, Inc. and introduced in 1999. TiVo provides an on-screen guide of scheduled broadcast programming television programs, whose features include "Season Pass" schedules which record every new episode of a series, and "WishList"...

units download guide data separately. TV Guide On Screen can also be used for this, but very few if any ATSC tuners include this (which requires downloading all guide data for all channels from one particular station). Stations sending the wrong time are also a major problem, as this can skew or ruin guide data for all stations until correct time is received again from a different and correctly-set station.

Manual tuning

Each digital OTA channel number is composed of a main number and a subchannel, for example 4.1, 4.2, etc. A dash is an alternate form of representation: 4-1, 4-2... The dot and dash are interchangeable; they both mean the same thing. The main channel numbers refer to the same radio frequencies as previously. However, now "virtual channel

Virtual channel

In telecommunications, a logical channel number , also known as virtual channel, is a channel designation which differs from that of the actual radio channel on which the signal travels....

" (technically known as logical channel number) numbers are common. So, Channel 4 digital signals may now actually be broadcast on channel 43, or any other frequency. When the ATSC tuner does a channel scan, it finds the signal on channel 43, learns that this material is called "Channel 4", and remembers that mapping. The user can tune to "4", and the tuner will know to tune in 43. Before a scan is done, it may be possible to access the programs directly by manual tuning, by entering 43-1, 43-2... After the scan, the programs would usually be accessed by entering 4-1, 4-2 etc, but it may still be possible to also access them directly at 43. If stations change their broadcast frequencies, it may be possible to access the new frequencies directly, but the usual procedure is to rescan all of the channels.

A complete table of US station assignments is here:
Tentative Digital Television (DTV) Channel assignment

The actual channel frequencies are listed here:
Television Frequency Table

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Technical overview

How an ATSC Tuner Works

Selective tuning

Demodulation

Transport stream

Decompression

Error correction

AV synchronization

Image reformatting

United States government mandates

Analog TV broadcast switch-off

Canadian government mandates

Setup and operation

Manual tuning

See also

External links