Multichannel television sound
Encyclopedia
Multichannel television sound, better known as MTS (often still as BTSC, for the Broadcast Television Systems Committee that created it), is the method of encoding
three additional channels
of audio
into an NTSC
-format audio
carrier
.
as the U.S.
standard
for stereo
television
transmission
in 1984. Initial work on design and testing of a stereophonic audio system began in 1975 when Telesonics approached Chicago
public television station WTTW
. WTTW was producing a music show titled Soundstage
at that time, and was simulcasting the stereo audio mix on local FM
stations. Telesonics and WTTW formed a working relationship and began developing the system which was similar to FM stereo modulation. Twelve WTTW studio and transmitter engineers added the needed broadcast experience to the relationship. The Telesonics system was tested and refined using the WTTW transmitter facilities on the Sears Tower. In 1979, WTTW had installed a stereo Grass Valley master control switcher, and had added a second audio channel to the microwave STL (Studio Transmitter Link). By that time, WTTW engineers had further developed stereo audio on videotape recorders in their plant, using split audio track heads manufactured to their specifications, outboard record electronics, and Dolby noise reduction that allowed Soundstage to be recorded and electronically edited. In addition, an Ampex
MM1100, 24-track audio recorder was also used for music production and mixing. PBS
member stations who wished to deliver Soundstage in stereo were provided with a four-track (left, right, vertical drive, and time code
) audio tape that could be synced with the video machines in those cities.
During the FCC approval process, several manufacturers applied to the FCC for consideration. Most notably the Electronic Industries Alliance
(EIA) and Japanese EIA asked to be included in order to represent their members in the testing and specification phases of the approval process. WTTW engineers helped set standards for frequency response
, separation, and other uses of the spectrum. They also provided program source material used for the testing and maintained the broadcast chain. A 3M
24-track audio recorder was used to allow the selection of 12 different stereo programs for testing. The Matsushita Quasar TV manufacturing plant and laboratory, just west of Chicago, was used as the source for all testing of the competing systems. Following the testing, several questions were raised about the validity of some of the tests, and a second round of testing began.
WTTW installed a Broadcast Electronics prototype stereo modulator in October 1983, and began full-time broadcasting in stereo at that time using the Telesonics system prior to FCC rule-making on the BTSC system. Following EIA and FCC recommendations, the BE modulator was modified to meet BTSC specifications, and by August 1984 was in full-time use on WTTW.
Sporadic network transmission of stereo audio began on NBC on July 26, 1984, with The Tonight Show Starring Johnny Carson
, although at the time only the network's New York City flagship station, WNBC
, had stereo broadcast capability; regular stereo transmission of NBC programs began during early 1985. ABC and CBS followed suit in 1986 and 1987, respectively. FOX
was the last network to join around 1990, with the four networks having their entire prime-time schedules in stereo by late 1994 (The WB and UPN
, launched the following season with their entire line-ups in stereo). One of the first television receiving systems to include BTSC capability was the RCA Dimensia
, released in 1984.
From the mid-1980s to the mid-1990s and also in the 2000's, the networks would display the disclaimer "In stereo (where available)" at the beginning of stereo programming;
(the left plus right stereo sum) audio track.
In other words the normal mono television audio consists of L+R information. A second signal (MTS) rides on top of this mono carrier wave. This MTS signal consists of L minus R.
The stereo information is dbx
-encode
d to increase the signal-to-noise ratio
(at low levels), to aid in noise reduction.
, every TV device that decoded MTS originally required the payment of royalties
, first to dbx, Inc.
, then to THAT Corporation which was spun off from dbx in 1989 and acquired its MTS patents in 1994; however, those patents expired worldwide in 2004. Though THAT now owns some patents related to digital implementations of MTS, a letter from THAT to the National Telecommunications and Information Administration
in 2007 confirms that no license is required from THAT for all analog and some digital implementations of MTS.
(SAP) also is part of the standard, providing another language
, a video description service like DVS
, or a completely separate service like a campus radio
station or weatheradio
.
A third PRO (professional) channel is provided for internal use by the station, and may handle audio or data. The PRO channel is normally used with electronic news gathering
during news
broadcast
s to talk to the remote location (such as a reporter on-location), which can then talk back through the remote link
to the TV station.
MTS signals are indicated to the television receiver by adding a 15.734 kHz pilot tone to the signal.
The MTS pilot is locked or derived from the horizontal sync signal used to lock the video display. Variations in phase or frequency of the horizontal sync are therefore transferred to the audio. UHF transmitters in use in 1984 generally had significant phase errors introduced in this signal making the transmission of stereo audio on UHF stations of that time nearly impossible. Later refinements in UHF transmitters minimized these effects and allowed stereo transmission for those stations.
. It remains in use in LPTV and in analogue cable television
. All coupon-eligible converter box
es (CECBs) are required to output stereo sound
via RCA connector
s, but MTS is merely an optional requirement for the RF modulator
that every CECB contains. NTIA has stated that MTS was made optional for cost reasons; this may have been due to a belief that MTS still required royalty payments to THAT Corporation, which is no longer true except for some digital implementations.
THAT has created consumer pages on the DTV transition and how it affects MTS. The site describes the situation by stating that most consumers with CECBs will end up with monaural
TV sound, since RF-only connections are common and MTS is optional (and rare) for CECBs.
Encoder
An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.-Media:...
three additional channels
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...
of audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
into an 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...
-format audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
carrier
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...
.
History
Multichannel Television Sound was adopted by the Federal Communications CommissionFederal 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...
as the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
standard
Standardization
Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
for stereo
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
in 1984. Initial work on design and testing of a stereophonic audio system began in 1975 when Telesonics approached Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
public television station WTTW
WTTW
WTTW channel 11 is one of three Public Broadcasting Service member public television stations serving the Chicago, Illinois market; the others are WYCC and WYIN. WTTW began broadcasting on September 6, 1955 and it is owned and operated by Window to the World Communications, Inc., a not-for-profit...
. WTTW was producing a music show titled Soundstage
Soundstage (TV program)
Soundstage is an American live concert television series produced by WTTW Chicago and HD Ready. The original series aired for 13 seasons between 1974 and 1985; a new series of seasons began in 2003, with the latest running through summer 2009, each presented in high definition with surround...
at that time, and was simulcasting the stereo audio mix on local FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
stations. Telesonics and WTTW formed a working relationship and began developing the system which was similar to FM stereo modulation. Twelve WTTW studio and transmitter engineers added the needed broadcast experience to the relationship. The Telesonics system was tested and refined using the WTTW transmitter facilities on the Sears Tower. In 1979, WTTW had installed a stereo Grass Valley master control switcher, and had added a second audio channel to the microwave STL (Studio Transmitter Link). By that time, WTTW engineers had further developed stereo audio on videotape recorders in their plant, using split audio track heads manufactured to their specifications, outboard record electronics, and Dolby noise reduction that allowed Soundstage to be recorded and electronically edited. In addition, an Ampex
Ampex
Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...
MM1100, 24-track audio recorder was also used for music production and mixing. PBS
Public Broadcasting Service
The Public Broadcasting Service is an American non-profit public broadcasting television network with 354 member TV stations in the United States which hold collective ownership. Its headquarters is in Arlington, Virginia....
member stations who wished to deliver Soundstage in stereo were provided with a four-track (left, right, vertical drive, and time code
Time code
A timecode is a sequence of numeric codes generated at regular intervals by a timing system.- Video and film timecode :...
) audio tape that could be synced with the video machines in those cities.
During the FCC approval process, several manufacturers applied to the FCC for consideration. Most notably the Electronic Industries Alliance
Electronic Industries Alliance
The Electronic Industries Alliance was a standards and trade organization composed as an alliance of trade associations for electronics manufacturers in the United States. They developed standards to ensure the equipment of different manufacturers was compatible and interchangeable...
(EIA) and Japanese EIA asked to be included in order to represent their members in the testing and specification phases of the approval process. WTTW engineers helped set standards for frequency response
Frequency response
Frequency response is the quantitative measure of the output spectrum of a system or device in response to a stimulus, and is used to characterize the dynamics of the system. It is a measure of magnitude and phase of the output as a function of frequency, in comparison to the input...
, separation, and other uses of the spectrum. They also provided program source material used for the testing and maintained the broadcast chain. A 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
24-track audio recorder was used to allow the selection of 12 different stereo programs for testing. The Matsushita Quasar TV manufacturing plant and laboratory, just west of Chicago, was used as the source for all testing of the competing systems. Following the testing, several questions were raised about the validity of some of the tests, and a second round of testing began.
WTTW installed a Broadcast Electronics prototype stereo modulator in October 1983, and began full-time broadcasting in stereo at that time using the Telesonics system prior to FCC rule-making on the BTSC system. Following EIA and FCC recommendations, the BE modulator was modified to meet BTSC specifications, and by August 1984 was in full-time use on WTTW.
Sporadic network transmission of stereo audio began on NBC on July 26, 1984, with The Tonight Show Starring Johnny Carson
The Tonight Show Starring Johnny Carson
The Tonight Show Starring Johnny Carson is a talk show hosted by Johnny Carson under the Tonight Show franchise from 1962 to 1992. It originally aired during late-night....
, although at the time only the network's New York City flagship station, WNBC
WNBC
WNBC, virtual channel 4 , is the flagship station of the NBC television network, located in New York City. WNBC's studios are co-located with NBC corporate headquarters at 30 Rockefeller Plaza in midtown Manhattan...
, had stereo broadcast capability; regular stereo transmission of NBC programs began during early 1985. ABC and CBS followed suit in 1986 and 1987, respectively. FOX
Fox Broadcasting Company
Fox Broadcasting Company, commonly referred to as Fox Network or simply Fox , is an American commercial broadcasting television network owned by Fox Entertainment Group, part of Rupert Murdoch's News Corporation. Launched on October 9, 1986, Fox was the highest-rated broadcast network in the...
was the last network to join around 1990, with the four networks having their entire prime-time schedules in stereo by late 1994 (The WB and UPN
UPN
United Paramount Network was a television network that was broadcast in over 200 markets in the United States from 1995 to 2006. UPN was originally owned by Viacom/Paramount and Chris-Craft Industries, the former of which, through the Paramount Television Group, produced most of the network's...
, launched the following season with their entire line-ups in stereo). One of the first television receiving systems to include BTSC capability was the RCA Dimensia
RCA Dimensia
Dimensia was RCA's brand name for their high-end models of television systems and their produced from 1984 to 1989, with variations continuing into the early 1990s, superseded by the ProScan model line. After RCA was acquired by General Electric in 1986, GE sold the RCA consumer electronics line...
, released in 1984.
From the mid-1980s to the mid-1990s and also in the 2000's, the networks would display the disclaimer "In stereo (where available)" at the beginning of stereo programming;
- NBC would use the image of a television with headphones displaying the NBC Peacock in blue for their "bugDigital on-screen graphicA digital on-screen graphic is a watermark-like station logo that many television broadcasters overlay over a portion of the screen-area of their programs to identify the channel...
" with the above disclaimer to the right of the image. - CBS displayed a blue or white bar with the words CBS StereoSound (CBS' stereo sound system) emanating from a central position on the screen.
- ABC used a simple In stereo where available disclaimer equivalent to the CBS version until 1989, when it was reduced further to Stereo: Where available. The display was discontinued in 1991 when the network left display of the stereo tag to show producers.
- Fox used white cursiveCursiveCursive, also known as joined-up writing, joint writing, or running writing, is any style of handwriting in which the symbols of the language are written in a simplified and/or flowing manner, generally for the purpose of making writing easier or faster...
text being "written" on the screen with their stereo bug until fall 1993. Unlike the latter cases however where it was displayed only at a master controlMaster controlMaster control is the technical hub of a broadcast operation common among most over-the-air television stations and television networks. It is distinct from a production control room in television studios where the activities such as switching from camera to camera are coordinated...
level at the time of the program broadcast, the producers of each program inserted the logo within their title sequenceTitle sequenceA Title Sequence is the method by which cinematic films or television programs present their title, key production and cast members, or both, utilizing conceptual visuals and sound...
s directly, and in programs such as Married...with Children, In Living ColorIn Living ColorIn Living Color is an American sketch comedy television series, which originally ran on the Fox Network from April 15, 1990 to May 19, 1994. Brothers Keenen and Damon Wayans created, wrote, and starred in the program. The show was produced by Ivory Way Productions in association with 20th Century...
, and COPSCOPS (TV series)Cops is an American documentary/reality television series that follows police officers, constables, and sheriff's deputies during patrols and other police activities...
, the logo is still displayed to this day in syndicated airings of pre-1993 episodes of series carried on Fox, and are also part of TV on DVD prints. The same process was used for NBC's Saturday Night LiveSaturday Night LiveSaturday Night Live is a live American late-night television sketch comedy and variety show developed by Lorne Michaels and Dick Ebersol. The show premiered on NBC on October 11, 1975, under the original title of NBC's Saturday Night.The show's sketches often parody contemporary American culture...
due to that program's live production nature excluding attempts to remove the bug for tape airings.
Adopted in
It has also been adopted by- CanadaCanadaCanada 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...
for NTSCNTSCNTSC, 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... - MexicoMexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
for NTSCNTSCNTSC, 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... - ChileChileChile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
for NTSCNTSCNTSC, 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... - BrazilBrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
for PAL-M (television)PAL-M (television)PAL-M is the TV system used in Brazil since February 19, 1972. At that time, Brazil was the first South American country to broadcast in colour. Colour TV broadcast began on September 1972 when the TV networks Globo, Tupi and Bandeirantes TV transmitted the Caxias do Sul Grape Festival. Transition... - ArgentinaArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
for PAL-N - TaiwanTaiwanTaiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
for NTSCNTSCNTSC, 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... - PhilippinesPhilippinesThe Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
for NTSCNTSCNTSC, 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...
How MTS works
The first channel is the stereo difference (left minus right), used to add stereophonic sound to the existing monophonicMonaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
(the left plus right stereo sum) audio track.
In other words the normal mono television audio consists of L+R information. A second signal (MTS) rides on top of this mono carrier wave. This MTS signal consists of L minus R.
- When the two audio channels are added together, or summed (L+R plus L-R), the left channel is derived.
- When the second audio channel is subtracted from the first by a phase reversal (L+R minus L-R), the right channel is derived.
MTS real world performance
- In ideal circumstances MTS Stereo is about 1.5 db better in performance than standard VHF FM stereo.
- Usually with MTS, as with VHF FM stereo, a certain amount of crosstalk is encountered, limiting stereo separation.
The stereo information is dbx
Dbx (noise reduction)
dbx is a family of noise reduction systems developed by the company of the same name. The most common implementations are dbx Type I and dbx Type II for analog tape recording and, less commonly, vinyl LPs. A separate implementation, known as dbx-TV, is part of the MTS system used to provide stereo...
-encode
Encode
Encode may refer to:* Can be related to "Code"* Encode ApS, a Danish software company* Encode SA, a Greek information security company* ENCODE, the ENCyclopedia Of DNA Elements...
d to increase the signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
(at low levels), to aid in noise reduction.
MTS licensing
Because of the use of dbx compandingCompanding
In telecommunication, signal processing, and thermodynamics, companding is a method of mitigating the detrimental effects of a channel with limited dynamic range...
, every TV device that decoded MTS originally required the payment of royalties
Royalties
Royalties are usage-based payments made by one party to another for the right to ongoing use of an asset, sometimes an intellectual property...
, first to dbx, Inc.
Dbx, Inc.
dbx, Inc. is an American producer of professional audio recording equipment. It was founded by David E. Blackmer in 1971. The original company goal was: "To get closer to the realism of a live performance." Its early products were based on the concept of using decibel expansion which gave the...
, then to THAT Corporation which was spun off from dbx in 1989 and acquired its MTS patents in 1994; however, those patents expired worldwide in 2004. Though THAT now owns some patents related to digital implementations of MTS, a letter from THAT to the National Telecommunications and Information Administration
National Telecommunications and Information Administration
The National Telecommunications and Information Administration is an agency of the United States Department of Commerce that serves as the President's principal adviser on telecommunications policies pertaining to the United States' economic and technological advancement and to regulation of the...
in 2007 confirms that no license is required from THAT for all analog and some digital implementations of MTS.
How MTS audio channels are used
The second audio programSecond audio program
Second audio program , also known as secondary audio programming, is an auxiliary audio channel for analog television that can be broadcast or transmitted both over the air and by cable TV.-Usage:...
(SAP) also is part of the standard, providing another language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
, a video description service like DVS
Descriptive Video Service
The Descriptive Video Service is a major United States producer of video description, which makes visual media, such as television programs, feature films, and home videos, more accessible to people who are blind or otherwise visually impaired...
, or a completely separate service like a campus radio
Campus radio
Campus radio is a type of radio station that is run by the students of a college, university or other educational institution. Programming may be exclusively by students, or may include programmers from the wider community in which the radio station is based...
station or weatheradio
Weatheradio
A weather radio service is a broadcast service that airs weather reports. When the radio is on and tuned to the weather band, it airs both normal and emergency weather information...
.
A third PRO (professional) channel is provided for internal use by the station, and may handle audio or data. The PRO channel is normally used with electronic news gathering
Electronic news gathering
ENG is a broadcasting industry acronym which stands for electronic news gathering. It can mean anything from a lone broadcast journalist reporter taking a single professional video camera out to shoot a story, to an entire television crew taking a production truck or satellite truck on location...
during news
News
News is the communication of selected information on current events which is presented by print, broadcast, Internet, or word of mouth to a third party or mass audience.- Etymology :...
broadcast
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
s to talk to the remote location (such as a reporter on-location), which can then talk back through the remote link
Remote pickup unit
A remote pickup unit or RPU is a radio system using special radio frequencies set aside for electronic news gathering and remote broadcasting. It can also be used for other types of point-to-point radio links....
to the TV station.
- Specialized receiversReceiver (radio)A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
for the PRO channel are generally only sold to broadcast professionals. - NICAMNICAMNear Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...
has a similar pro-channel feature that has only been implemented in the UK (http://stoneship.org.uk/~steve/nicam.html#SPARE).
MTS signals are indicated to the television receiver by adding a 15.734 kHz pilot tone to the signal.
The MTS pilot is locked or derived from the horizontal sync signal used to lock the video display. Variations in phase or frequency of the horizontal sync are therefore transferred to the audio. UHF transmitters in use in 1984 generally had significant phase errors introduced in this signal making the transmission of stereo audio on UHF stations of that time nearly impossible. Later refinements in UHF transmitters minimized these effects and allowed stereo transmission for those stations.
MTS and the DTV transition in the United States
As a component of the NTSC standard, MTS is no longer being used in U.S. full-power television broadcasting after the June 12, 2009 DTV transition in the United StatesDTV transition in the United States
The DTV transition in the United States was the switchover from analog to exclusively digital broadcasting of free over-the-air television programming...
. It remains in use in LPTV and in analogue cable television
Cable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
. All 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...
es (CECBs) are required to output stereo sound
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
via RCA connector
RCA connector
An RCA connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals...
s, but MTS is merely an optional requirement for the RF modulator
RF modulator
An RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
that every CECB contains. NTIA has stated that MTS was made optional for cost reasons; this may have been due to a belief that MTS still required royalty payments to THAT Corporation, which is no longer true except for some digital implementations.
THAT has created consumer pages on the DTV transition and how it affects MTS. The site describes the situation by stating that most consumers with CECBs will end up with monaural
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
TV sound, since RF-only connections are common and MTS is optional (and rare) for CECBs.
See also
- NICAMNICAMNear Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...
- ZweikanaltonZweikanaltonZweikanalton is a television sound transmission system used in Germany, Austria, Switzerland, and other countries that use or used PAL-B or PAL-G...
- Secondary Audio Program