Digital subchannel
Encyclopedia
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 program stream, and multiplexing
to combine them into a single signal. The practice is sometimes called multicasting.
-standard digital television in the United States
supports multiple program streams over-the-air, using a virtual channel
numbering scheme in which the television channel
number is suffixed with ".2" or ".3" to indicate a second or third television program
carried by the same television station
at the same time. (By convention, ".1" is normally used to refer to the digital version of the station's main signal and the ".0" position is reserved for analog channels.)
For instance, an Ion Television station could use one digital signal to carry three or more subchannels in a format such as:
Trinity Broadcasting Network
stations use five SDTV channels, the most of any large broadcaster in the country. Smaller stations, willing to compromise on broadcast quality, have been able to fit many more channels into a space. KAXT-CA
in San Francisco is believed to have the most feeds of any individual over-the-air broadcaster, with twelve video feeds (all SDTV) and several audio feeds (WANN-LD in Atlanta, Georgia
, with ten video and six audio feeds, comes in close second); several cable-to-air broadcasters have (such as one in Cortez, Colorado
) multiplex more than five separate cable television channels into subchannels of one signal.
In the realm of digital cable
(which traditionally does not use subchannels), Music Choice
has all of its nearly 50 music channels (including SWRV
) packaged as digital subchannels on one channel. This is possible as the only information sent in each channel is the audio, along with a still slide which rotates every twenty seconds displaying artist/title/album information and a still ad, freeing up significant bandwidth for more subchannels.
This would represent a significant cost, power and bandwidth savings for a broadcaster in comparison to the cost of operating additional analog TV stations to accommodate the extra programming. In practice, operating extra stations is impossible, due to required channel and distance separations and the available number of channels.
Most ATSC tuner
s will automatically add a new digital subchannel to the internal channel map, once it is tuned to the station carrying the new channel. However, some of these will not delete the channel if it is removed by the station.
Mobile DTV is also carried on ATSC stations, but as a separate service, according to the ATSC-M/H
standard.
The FCC considers all subchannels of a single station to have the same call letters for legal ID purposes. However, within the broadcast sales industry, to differentiate subchannels, the initial letter of a call sign changes per subchannel. The typical pattern is, if subchannel 0.1 is WXMP, then 0.2 is EXMP, 0.3 is GXMP, and 0.4 is DXMP; if subchannel 0.1 is KXMP, then 0.2 is NXMP, 0.3 is OXMP, ans 0.4 is PXMP.
-standard digital television in El Salvador
supports multiple program streams over-the-air, using a virtual channel
numbering scheme in which the channel number is suffixed with ".2" or ".3" to indicate a second or third program carried by the same station at the same time. (By convention, ".1" is normally used to refer to the digital version of the station's main signal and the ".0" position is reserved for analog channels.)
This would represent a significant cost, power and bandwidth savings for a broadcaster in comparison to the cost of operating additional analog TV stations to accommodate the extra programming. In practice, operating extra stations is impossible, due to required channel and distance separations and the available number of channels.
Most ATSC tuner
s will automatically add a new digital subchannel to the internal channel map, once it is tuned to the station carrying the new channel. However, some of these will not delete the channel if it is removed by the station.
Mobile DTV will be also carried on ATSC stations, but as a separate service, according to the ATSC-M/H
standard.
SBS and ABC
).
Currently, SBS, ABC
, Seven
, Nine
and Ten show one high-definition subchannel each (SBS HD, ABC News 24
, 7mate
, GEM and One respectively); except for SBS One, these notably do not consist of the same content as the primary television channel.
Inclusive of their primary standard definition channels (ignoring HD):
SBS offers two unique SD subchannels;
ABC
offers three unique SD subchannels;
Seven
offers two unique SD subchannels;
Nine
offers two unique SD subchannels;
Ten offers two unique SD subchannels.
Community television stations also broadcast digital television stations in Sydney (TVS
), Melbourne and Geelong (C31), Adelaide (44 Adelaide) and Brisbane (31 Digital) however they typically only broadcast a single SD subchannel which consists of the primary television channel.
There have been a number of issues surrounding the introduction of digital subchannels in Australia. The first subchannels launched by the ABC, ABC Kids and Fly TV
, closed after less than two years in operation in 2003 due to lack of budget and lack of viewers, and commercial broadcasters could not legally air a digital subchannel other than a single high-definition service until 2009.
currently has four of its digital channels (ITV1
, ITV2
, ITV3
and ITV4
) broadcasting on one multiplex, while two others (ITV2 +1
and CITV) are each broadcast on another, separate, multiplex.
and Brazil
, ISDB
(similar to DVB) is used, and was specifically designed with physical RF
segments that could be split to use for different subchannels.
. A station carrying multiple subchannels will normally limit itself to one high-definition channel, with the additional channels being carried in standard definition. Because of the tradeoffs, stations owned by CBS Corporation
that are a part of CBS Television Stations
(which include CBS
O&O's
, CW O&O's
, and some independent station
s) are not permitted to have digital subchannels.
It is, however, possible for stations to carry two subchannel feeds in HD, though it is still extremely rare. Some examples of stations broadcasting in this format are:
Outside of the United States, especially in Europe, high-definition feeds are rarer, and most countries only provide a single high-definition service for each broadcaster. For example, digital television in France
only has five HD services, one each for TF1
, France 2
, Canal+
, M6 and Arte
, and the United Kingdom is currently broadcasting four HD services over terrestrial frequencies including BBC One HD, BBC HD
, ITV1 HD, and Channel 4 HD (S4C Clirlun is broadcast in Wales instead of Channel 4 HD).
(PBS) stations around the United States broadcast four SD channels during the daytime, and one HD and one SD channel at night. PBS stations often carry additional national channels such as PBS HD (PBS Satellite Service), PBS Kids Sprout
, PBS World
, Create, PBS Learner (The Annenberg Channel
) or the Spanish-language V-me
network. MHz Networks
transmits to the Washington, D.C.
area on ten subchannels transmitted by two stations, with virtual channel
numbering making them appear as one station.
In some US states, state-wide educational, cultural or public-affairs
services are carried by existing PBS member stations on digital subchannels; these include regional services such as the Minnesota Channel
, Wisconsin Channel or New York State broadcaster ThinkBright TV. The use of subchannels has also allowed educational television
broadcasters to sell off former secondary PBS analogue stations (such as WNEQ in Buffalo
to LIN TV
to become CW affiliate WNLO
) to commercial broadcasters
, as the additional educational content these once provided can now be carried by multiple subchannels of the one main station. Subchannels also allow stations to devote an entire channel to telecourses
which are recorded by instructors and students for later use, freeing the original channel to air a more general schedule in the morning and overnight hours
.
s in the United States, one or more national networks are unavailable from local over-the-air
sources. A small city with only one or two commercial stations would not be able to carry the full programming lineup from all four largest commercial networks (CBS
, NBC
, ABC
, Fox
) in analogue as one station could only broadcast one program at a time. This limitation could be overcome by adding the additional networks as digital subchannels of existing local commercial stations. One prime example of this is in the Wheeling, West Virginia
/Steubenville, Ohio
market, which for decades has had only two television stations (CBS
affiliate WTRF-TV
and NBC
affiliate WTOV-TV
, as well as cable-only CW affiliate WBWO
) and had to mostly rely on stations in Pittsburgh (and to a lesser extent Columbus
and Youngstown, Ohio
) for other networks. However, the advent of digital television has allowed WTRF to launch two digital channels (one for Fox with MyNetworkTV as a secondary affiliate, the other for ABC) while still airing the full CBS schedule on its main signal.
Digital subchannels also help expand the traditional coverage areas of a station beyond their former analog boundaries. In the Upper Peninsula of Michigan
and northern Minnesota
, many of those stations are on duplicate frequencies to cover a large market area. This is used to duplicate network service for stations which are part of duopolies
, where transmitters scattered through a large geographical area allow multiple networks and channels to be carried.
The most prominent example is Duluth, Minnesota
's Northland's NewsCenter
quadopoly of stations from Granite Broadcasting, which consists of two traditional broadcasters, NBC station KBJR
and CBS affiliate KDLH
, and three subchannels, CW Plus affiliate Northland CW 2
, My9
, the area's MyNetworkTV station, and a local weather station. While KDLH carries CW2 on their DT2 signal and My9 airs on KBJR-DT2 on their traditional Duluth signal, all five channels are carried on Chisholm
-based sister station KRII to the north for the Iron Range
region, providing that area stations which were previously unavailable over-the-air.
This is also the case with Upper Michigan station WPBN/WTOM
, which also airs the signals of sister station WGTU/WGTQ
, providing WGTU/WGTQ's ABC programming across a wider coverage area, while WWTV/WWUP
carries their sister Fox station WFQX
on their DT2 subchannel to expand their coverage area further north into the eastern portion of the Upper Peninsula.
In many cases, these "new" channels are existing secondary channels which were carried by a low-power or Class A station
or by a cable television
channel. Often, a full-power TV station acquires or already owns a low-power secondary station in the same market to carry a second network. The use of a digital subchannel on a full power TV station as a replacement for LPTV greatly increases coverage areas for this programming.
With the launches of The CW
and MyNetworkTV
, many television stations have been launching subchannels affiliating with these secondary networks.
Because of the nature of transmissions in the low VHF band (channels 2 through 6), some stations using these frequencies are relayed on the subchannels of stations that use more advantageous frequencies. An example of this is WRGB
, the CBS affiliate of Albany, New York
. While WRGB broadcasts in high-definition on channel 6, a standard-definition feed of WRGB can also be seen as a subchannel of CW affiliate (and duopoly
partner) WCWN
, on channel 45.
Other stations have launched separate independent station
s on their DT-2 signals.
and Untamed Sports TV
) have been launched for TV stations digital subchannels. A common use for digital subchannels is for CBS
affiliates to show all of the early round games of the NCAA Basketball Tournament
on their digital channel, which is subdivided into four different subchannels. (Most of the major professional sports leagues, however, have strict prohibitions against this and only allow one game to be aired in a market at one time; all four of the major leagues have out-of-market sports package
s that require a paid subscription and generate significant revenue for the leagues.)
have been created to serve this audience.
and .2 Network
) have been launched for TV stations digital subchannels. Some TV stations (such as K38IZ-D in Phoenix, Arizona
) broadcast classic TV shows and music video
s on their digital subchannels. Music-video formats have also been tried as digital subchannels on terrestrial stations.
and Mexicanal
) have been launched for TV stations digital subchannels.
(ABC, Little Rock) was forced to follow this path in 2008, moving its digital signal to a subchannel of local MyNetworkTV
affiliate KWBF after a tower collapse
knocked its main signal off-air. The virtual channel
numbering scheme allows an existing licensed broadcaster to keep its displayed channel number unchanged (KATV ABC 7 in this case) even if the signal is carried physically as a subchannel of some other local station.
During the Station Fire in 2009, Los Angeles station KNBC
temporarily replaced NBC Plus and Universal Sports
on its subchannels with standard-definition feeds from sister stations KWHY-TV
(independent) and KVEA
(Telemundo) as an emergency measure in the event those stations' transmitters were destroyed or disabled as the fire reached the Mount Wilson
transmitter site for most Los Angeles area stations.
broadcast radio station
among their subchannel offerings (for instance, KCSM-TV
in San Mateo, California
broadcasts KCSM FM on its DT3 signal). WANN-LD in Atlanta
offers six radio stations owned by Clear Channel Communications
, in addition to ten TV channels. This type of service is known as DTV radio.
Non-broadcast content, subscription TV channels or datacasting
operations unrelated to the main TV programming are also permitted by the DTV standards but are less-commonly used. USDTV
was an over-the-air pay TV
service that used H.264 compression instead of standard MPEG-2
. Mobile DTV now uses MPEG-4
compression, which like H.264 yields a much lower bitrate
for the same video quality
. For example, the Sezmi TV/DVR service uses broadcast digital sub-channels (not in the clear) in selected cities to stream a limited number of "cable" channels to its subscribers for an additional fee to supplement its otherwise free Digital video recorder
(DVR) service allowing recordings of local broadcast channels and free and subscription internet content.
is divided. Therefore, station managers and broadcast engineers could run any of the following scenarios using one 6 MHz channel (note that the actual bitrate moves up and down, due to usage of variable bitrate
encoding):
With improvements in MPEG encoding, and tighter VBR
encoding, more subchannels can be combined. 1×720p + 4×480i is becoming more common.
For a frame rate
of 30p
or 60i, uncompressed DTV channels have the following data rate
s in megapixels per second:
For ATSC
, these must be compressed into 19.4Mb/s total per physical 6 MHz RF
channel over the air, and 38.8Mb/s for cable.
also allow for multiple program streams.
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...
or 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...
station
Broadcast station
A broadcast station may be:*a radio station*a television stationIt does not include radio networks or television networks.-See also:*Broadcasting*Broadcast network*Station...
on the same 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...
channel. This is done by using data compression
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....
techniques to reduce the size of each individual program stream, and multiplexing
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...
to combine them into a single signal. The practice is sometimes called multicasting.
United States
ATSCATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
-standard digital television in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
supports multiple program streams over-the-air, using a 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....
numbering scheme in which the 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...
number is suffixed with ".2" or ".3" to indicate a second or third television program
Television program
A television program , also called television show, is a segment of content which is intended to be broadcast on television. It may be a one-time production or part of a periodically recurring series...
carried by the same 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...
at the same time. (By convention, ".1" is normally used to refer to the digital version of the station's main signal and the ".0" position is reserved for analog channels.)
For instance, an Ion Television station could use one digital signal to carry three or more subchannels in a format such as:
| Subchannel | Format | Program |
|---|---|---|
| 16.1 | 720p 720p 720p is the shorthand name for 1280x720, a category of High-definition television video modes having a resolution of 1080 or 720p and a progressive scan... |
ION |
| 16.2 | 480i 480i 480i is the shorthand name for a video mode, namely the US NTSC television system or digital television systems with the same characteristics. The i, which is sometimes uppercase, stands for interlaced, the 480 for a vertical frame resolution of 480 lines containing picture information; while NTSC... |
qubo Qubo Qubo is a multi-platform children's television specialty channel endeavor operated as a joint venture between ION Media Networks, NBCUniversal, Nelvana, Scholastic Corporation, and Classic Media... |
| 16.3 | ION Life ION Life ION Life is a digital television network carried by ION Television affiliates, airing lifestyle programming during the day, and movies in the evening. It was launched February 19, 2007... |
|
Trinity Broadcasting Network
Trinity Broadcasting Network
The Trinity Broadcasting Network is a major American Christian television network. TBN is based in Costa Mesa, California, with auxiliary studio facilities in Irving, Texas; Hendersonville, Tennessee; Gadsden, Alabama; Decatur, Georgia; Miami, Florida; Tulsa, Oklahoma; Orlando, Florida; and New...
stations use five SDTV channels, the most of any large broadcaster in the country. Smaller stations, willing to compromise on broadcast quality, have been able to fit many more channels into a space. KAXT-CA
KAXT-CA
KAXT-CD is a low-powered analog and digital television station licensed to Santa Clara, California. Founded May 31, 1989, the station is owned by Broadland Properties, Inc.-History:KAXT-CA was a low-power analog class-A television station...
in San Francisco is believed to have the most feeds of any individual over-the-air broadcaster, with twelve video feeds (all SDTV) and several audio feeds (WANN-LD in Atlanta, Georgia
Atlanta, Georgia
Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...
, with ten video and six audio feeds, comes in close second); several cable-to-air broadcasters have (such as one in Cortez, Colorado
Cortez, Colorado
The city of Cortez is a Home Rule Municipality that is the county seat and the most populous city of Montezuma County, Colorado, United States. The city population was 8,482 at the 2010 census...
) multiplex more than five separate cable television channels into subchannels of one signal.
In the realm of digital cable
Digital cable
Digital cable is a generic term for any type of cable television distribution using digital video compression or distribution. The technology was originally developed by Motorola.-Background:...
(which traditionally does not use subchannels), Music Choice
Music Choice
Music Choice is a United States company that programs music and produces music-related content for digital cable, cell phones, and cable modem subscribers in the US. Music Choice programs dozens of audio music channels for digital cable subscribers, as well as programs and produces music-related...
has all of its nearly 50 music channels (including SWRV
SWRV
SWRV is a music video television channel from Music Choice that launched on February 10, 2010.Programming on SWRV is interactive, based entirely on audience participation...
) packaged as digital subchannels on one channel. This is possible as the only information sent in each channel is the audio, along with a still slide which rotates every twenty seconds displaying artist/title/album information and a still ad, freeing up significant bandwidth for more subchannels.
This would represent a significant cost, power and bandwidth savings for a broadcaster in comparison to the cost of operating additional analog TV stations to accommodate the extra programming. In practice, operating extra stations is impossible, due to required channel and distance separations and the available number of channels.
Most ATSC tuner
ATSC tuner
An ATSC tuner, often called an ATSC receiver or HDTV tuner is a type of television tuner that allows reception of digital television television channels transmitted by television stations in North America, parts of Central America and South Korea that use ATSC standards...
s will automatically add a new digital subchannel to the internal channel map, once it is tuned to the station carrying the new channel. However, some of these will not delete the channel if it is removed by the station.
Mobile DTV is also carried on ATSC stations, but as a separate service, according to the ATSC-M/H
ATSC-M/H
ATSC-M/H is a standard in the USA for mobile digital TV, that allows TV broadcasts to be received by mobile devices.....
standard.
The FCC considers all subchannels of a single station to have the same call letters for legal ID purposes. However, within the broadcast sales industry, to differentiate subchannels, the initial letter of a call sign changes per subchannel. The typical pattern is, if subchannel 0.1 is WXMP, then 0.2 is EXMP, 0.3 is GXMP, and 0.4 is DXMP; if subchannel 0.1 is KXMP, then 0.2 is NXMP, 0.3 is OXMP, ans 0.4 is PXMP.
Canada
Although digital services in Canada use the same technology as the United States, none of the stations currently available in digital are broadcasting any subchannel other than a possible HD service.El Salvador
ATSCATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
-standard digital television in El Salvador
El Salvador
El Salvador or simply Salvador is the smallest and the most densely populated country in Central America. The country's capital city and largest city is San Salvador; Santa Ana and San Miguel are also important cultural and commercial centers in the country and in all of Central America...
supports multiple program streams over-the-air, using a 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....
numbering scheme in which the channel number is suffixed with ".2" or ".3" to indicate a second or third program carried by the same station at the same time. (By convention, ".1" is normally used to refer to the digital version of the station's main signal and the ".0" position is reserved for analog channels.)
This would represent a significant cost, power and bandwidth savings for a broadcaster in comparison to the cost of operating additional analog TV stations to accommodate the extra programming. In practice, operating extra stations is impossible, due to required channel and distance separations and the available number of channels.
Most ATSC tuner
ATSC tuner
An ATSC tuner, often called an ATSC receiver or HDTV tuner is a type of television tuner that allows reception of digital television television channels transmitted by television stations in North America, parts of Central America and South Korea that use ATSC standards...
s will automatically add a new digital subchannel to the internal channel map, once it is tuned to the station carrying the new channel. However, some of these will not delete the channel if it is removed by the station.
Mobile DTV will be also carried on ATSC stations, but as a separate service, according to the ATSC-M/H
ATSC-M/H
ATSC-M/H is a standard in the USA for mobile digital TV, that allows TV broadcasts to be received by mobile devices.....
standard.
Australia
Australian digital subchannels are currently divided between high definition, standard definition and radio subchannels (the latter only carried by non-commercialNon-commercial
Non-commercial refers to an activity or entity that does not in some sense involve commerce, at least relative to similar activities that do have a commercial objective or emphasis...
SBS and ABC
ABC Television
ABC Television is a service of the Australian Broadcasting Corporation launched in 1956. As a public broadcasting broadcaster, the ABC provides four non-commercial channels within Australia, and a partially advertising-funded satellite channel overseas....
).
Currently, SBS, ABC
ABC Television
ABC Television is a service of the Australian Broadcasting Corporation launched in 1956. As a public broadcasting broadcaster, the ABC provides four non-commercial channels within Australia, and a partially advertising-funded satellite channel overseas....
, Seven
Seven Network
The Seven Network is an Australian television network owned by Seven West Media Limited. It dates back to 4 November 1956, when the first stations on the VHF7 frequency were established in Melbourne and Sydney.It is currently the second largest network in the country in terms of population reach...
, Nine
Nine Network
The Nine Network , is an Australian television network with headquarters based in Willoughby, a suburb located on the North Shore of Sydney. For 50 years since television's inception in Australia, between 1956 and 2006, it was the most watched television network in Australia...
and Ten show one high-definition subchannel each (SBS HD, ABC News 24
ABC News 24
ABC News 24 is an Australian 24-hour news channel launched and owned by the Australian Broadcasting Corporation. The channel replaced the former ABC High Definition simulcast of ABC1 and commenced broadcasting at 7:30pm 5:30 on Thursday, 22 July 2010.-Pre-launch:The ABC announced in January 2010...
, 7mate
7mate
7mate is an Australian free-to-air high definition digital television channel, which was launched by the Seven Network on 25 September 2010.The network stated that 7mate would contain sport and regular programs aimed primarily at a male audience, with programming drawn from a combination of new...
, GEM and One respectively); except for SBS One, these notably do not consist of the same content as the primary television channel.
Inclusive of their primary standard definition channels (ignoring HD):
SBS offers two unique SD subchannels;
ABC
ABC Television
ABC Television is a service of the Australian Broadcasting Corporation launched in 1956. As a public broadcasting broadcaster, the ABC provides four non-commercial channels within Australia, and a partially advertising-funded satellite channel overseas....
offers three unique SD subchannels;
Seven
Seven Network
The Seven Network is an Australian television network owned by Seven West Media Limited. It dates back to 4 November 1956, when the first stations on the VHF7 frequency were established in Melbourne and Sydney.It is currently the second largest network in the country in terms of population reach...
offers two unique SD subchannels;
Nine
Nine Network
The Nine Network , is an Australian television network with headquarters based in Willoughby, a suburb located on the North Shore of Sydney. For 50 years since television's inception in Australia, between 1956 and 2006, it was the most watched television network in Australia...
offers two unique SD subchannels;
Ten offers two unique SD subchannels.
Community television stations also broadcast digital television stations in Sydney (TVS
Television Sydney
TVS, or Television Sydney , is a free-to-air community television station broadcasting in Sydney, Australia.-History:Transmissions officially commenced on analogue UHF channel 31 in February 2006 after three months of technical trials...
), Melbourne and Geelong (C31), Adelaide (44 Adelaide) and Brisbane (31 Digital) however they typically only broadcast a single SD subchannel which consists of the primary television channel.
There have been a number of issues surrounding the introduction of digital subchannels in Australia. The first subchannels launched by the ABC, ABC Kids and Fly TV
Fly TV
Fly TV was an ABC Television channel available to viewers of digital terrestrial television in Australia. The channel featured programming aimed towards teenagers and young adults. It was launched nationally on 1 November 2001, and aired alongside the children's-oriented ABC Kids Channel, which...
, closed after less than two years in operation in 2003 due to lack of budget and lack of viewers, and commercial broadcasters could not legally air a digital subchannel other than a single high-definition service until 2009.
Europe
As most digital services in Europe rely on more complex methods of multiplexing, where a large number of digital channels by many different broadcasters can be broadcast on one single frequency, the concept of a subchannel is instead applied to the variety of channels produced by a single company. This can vary widely depending on the country: for example, ITVITV
ITV is the major commercial public service TV network in the United Kingdom. Launched in 1955 under the auspices of the Independent Television Authority to provide competition to the BBC, it is also the oldest commercial network in the UK...
currently has four of its digital channels (ITV1
ITV1
ITV1 is a generic brand that is used by twelve franchises of the British ITV Network in the English regions, Wales, southern Scotland , the Isle of Man and the Bailiwicks of Jersey and Guernsey. The ITV1 brand was introduced by Carlton and Granada in 2001, alongside the regional identities of their...
, ITV2
ITV2
ITV2 is a 24 hour, free-to-air entertainment television channel in the United Kingdom owned by ITV Digital Channels Ltd, a division of ITV plc. It was launched on 7 December 1998, and is available on digital television via satellite, cable, IPTV and terrestrial platforms. The channel has the...
, ITV3
ITV3
ITV3 is an entertainment television channel in the United Kingdom that is owned by ITV Digital Channels Ltd, a division of ITV plc. The channel was launched on 1 November 2004. ITV3 is the second largest UK multi-channel, second only to ITV2.-History:...
and ITV4
ITV4
ITV4 is a British television station which was launched on 1 November 2005. It is owned by ITV Digital Channels Ltd, a division of ITV plc, and is part of the ITV network. The channel has a male-oriented line-up, including sport, cop shows and US comedies and dramas, as well as classic ITV action...
) broadcasting on one multiplex, while two others (ITV2 +1
ITV2
ITV2 is a 24 hour, free-to-air entertainment television channel in the United Kingdom owned by ITV Digital Channels Ltd, a division of ITV plc. It was launched on 7 December 1998, and is available on digital television via satellite, cable, IPTV and terrestrial platforms. The channel has the...
and CITV) are each broadcast on another, separate, multiplex.
ISDB television
In JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Brazil
Brazil
Brazil , 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...
, ISDB
ISDB
Integrated Services Digital Broadcasting is a Japanese standard for digital television and digital radio used by the country's radio and television stations. ISDB replaced the previously used MUSE "Hi-vision" analogue HDTV system...
(similar to DVB) is used, and was specifically designed with physical RF
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...
segments that could be split to use for different subchannels.
Tradeoffs
As the amount of data which can be carried on one digital television channel at one time is limited, the addition of multiple channels of programming as digital subchannels comes at the expense of having less available bandwidth for other purposes, such as high-definition televisionHigh-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...
. A station carrying multiple subchannels will normally limit itself to one high-definition channel, with the additional channels being carried in standard definition. Because of the tradeoffs, stations owned by CBS Corporation
CBS Corporation
CBS Corporation is an American media conglomerate focused on commercial broadcasting, publishing, billboards and television production, with most of its operations in the United States. The President and CEO of the company is Leslie Moonves. Sumner Redstone, owner of National Amusements, is CBS's...
that are a part of CBS Television Stations
CBS Television Stations
The CBS Television Stations are a group of television stations owned by CBS Corporation. As of 2009, CBS Corporation owns 28 stations, broken down as follows: 14 are the key stations of the CBS Television Network ; nine are aligned with the CW Television Network, which is co-owned by CBS with Time...
(which include CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
O&O's
Owned-and-operated station
In the broadcasting industry , an owned-and-operated station usually refers to a television station or radio station that is owned by the network with which it is associated...
, CW O&O's
The CW Television Network
The CW Television Network is a television network in the United States launched at the beginning of the 2006–2007 television season. It is a joint venture between CBS Corporation, the former owners of United Paramount Network , and Time Warner's Warner Bros., former majority owner of The WB...
, and some independent station
Independent station
An independent station is in the category of television terminology used to describe a television station broadcasting in the United States or Canada that is not affiliated with any television network....
s) are not permitted to have digital subchannels.
It is, however, possible for stations to carry two subchannel feeds in HD, though it is still extremely rare. Some examples of stations broadcasting in this format are:
- KXIIKXIIKXII, channel 12, is the CBS-affiliated television station for the Texoma region of Texas and Oklahoma. It is licensed to Sherman, Texas. Its transmitter is located southwest of Madill, Oklahoma...
, the CBSCBSCBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
affiliate in Sherman, TexasSherman, TexasSherman is a city in and the county seat of Grayson County, Texas, United States. The city's estimated population as of 2009 was 38,407. It is also one of two principal cities in the Sherman-Denison Metropolitan Statistical Area.-History:...
, airs FoxFox Broadcasting CompanyFox 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...
programming in HD on its third subchannelKXII-DT3KXII-DT3 is a subchannel of KXII known on-air as "Fox Texoma" and has been in operation since 2006. It is the first full time local Fox station for the Sherman-Ada DMA and broadcasts in 720p High Definition...
in addition to airing its main CBS programming in HD. The station also has a myNetworkTVMyNetworkTVMyNetworkTV is a television broadcast syndication service in the United States, owned by the Fox Entertainment Group, a division of News Corporation...
affiliate in SD on subchannel 12.2KXII-DT2KXII-DT2 is the MyNetworkTV-affiliated television station for the Texoma region of Texas and Oklahoma. The station is a second digital subchannel of CBS affiliate KXII that is owned by Gray Television. Over-the-air, it broadcasts a digital signal on VHF channel 12.2 from KXII's transmitter located...
.
- WGXAWGXAWGXA is the Fox affiliated television station for Central Georgia that is licensed to Macon. It broadcasts a high definition digital signal on UHF channel 16 from a transmitter on GA 87/U.S. 23/U.S. 129 Alternate along the Twiggs and Bibb County line. The station can also be seen on Cox channel 2...
, Fox's affiliate in Macon, GeorgiaMacon, GeorgiaMacon is a city located in central Georgia, US. Founded at the fall line of the Ocmulgee River, it is part of the Macon metropolitan area, and the county seat of Bibb County. A small portion of the city extends into Jones County. Macon is the biggest city in central Georgia...
, picked up the ABC affiliation on January 1, 2009 after former ABC station WPGA-TVWPGA-TVWPGA-TV is an Independent, Me-TV and Bounce TV affiliated television station serving Macon, Georgia and the Middle Georgia region. It broadcasts digitally on UHF channel 32...
dropped the network in a compensation and program content dispute, and is running two 720p720p720p is the shorthand name for 1280x720, a category of High-definition television video modes having a resolution of 1080 or 720p and a progressive scan...
HD signals for Fox and ABC (the native format for both networks) over their channel space. The original Fox channel is still branded via PSIP as Fox 24 and 24.1, while the ABC subchannel is known as ABC 16, using the physical digital channel 16 for their branding (and an eventual PSIP virtual channel of 16.2; currently 24.2 as problems are ironed out balancing the bandwidth needs of both signals).
- WKBN-TVWKBN-TVWKBN-TV is the CBS-affiliated television station for Youngstown, Ohio. It broadcasts a high definition digital signal on UHF channel 41 from a transmitter at WKBN's studios on Sunset Boulevard in Boardman Township. Owned by New Vision Television, WKBN is sister to and shares studios with low-power...
, the CBS affiliate in Youngstown, OhioYoungstown, OhioYoungstown is a city in the U.S. state of Ohio and the county seat of Mahoning County; it also extends into Trumbull County. The municipality is situated on the Mahoning River, approximately southeast of Cleveland and northwest of Pittsburgh, Pennsylvania...
which also owns & operates low-poweredLow-power broadcastingLow-power broadcasting is electronic broadcasting at very low power and low cost, to a small community area.The terms "low-power broadcasting" and "micropower broadcasting" should not be used interchangeably, because the markets are not the same...
Fox affiliate WYFX-LPWYFX-LPWYFX-LD is the Fox-affiliated television station for the Mahoning Valley of Northeastern Ohio, licensed to Youngstown. It broadcasts a low-powered digital signal UHF channel 19 from a transmitter on Sunset Boulevard in Boardman Township. Owned by New Vision Television, the station is sister to CBS...
, simulcasts WYFX on its second digital subchannel while broadcasting its main CBS feed on its first subchannel. Both subchannels are broadcasting in 720p720p720p is the shorthand name for 1280x720, a category of High-definition television video modes having a resolution of 1080 or 720p and a progressive scan...
HD, a reduction from CBS's preferred 1080i1080i1080i is the shorthand name for a high-definition television mode. The i means interlaced video; 1080i differs from 1080p, in which the p stands for progressive scan. The term 1080i assumes a widescreen aspect ratio of 16:9, implying a frame size of 1920×1080 pixels...
transmissions although Fox has a preference for 720p. Its sister station, ABCAmerican Broadcasting CompanyThe American Broadcasting Company is an American commercial broadcasting television network. Created in 1943 from the former NBC Blue radio network, ABC is owned by The Walt Disney Company and is part of Disney-ABC Television Group. Its first broadcast on television was in 1948...
affiliate WYTVWYTVWYTV is the ABC-affiliated television station for the Mahoning Valley of Northeastern Ohio and Northwestern Pennsylvania that is licensed to Youngstown. It broadcasts a high definition digital signal on UHF channel 36 from a transmitter on Shady Run Road in Boardman Township...
, is currently in the process of converting its MyNetworkTV subchannelWYTV-DT2WYTV-DT2 is the MyNetworkTV-affiliated television station for the Mahoning Valley of Northeastern Ohio and Northwestern Pennsylvania. It is a second digital subchannel of the area's ABC affiliate WYTV that is owned by PBC Broadcasting but operated by New Vision Television though a shared services...
into high-definition broadcasts. It currently also has a weatherWeatherWeather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
channel on its third subchannel, which currently has an uncertain future if WYTV-DT2 is converted to HD. Such a move would make the Youngstown DMA the only such market with two stations broadcasting two subchannels in HD.
- WPVI-TVWPVI-TVWPVI-TV, channel 6, is an owned-and-operated television station of the Walt Disney Company-owned American Broadcasting Company, located in Philadelphia, Pennsylvania, USA. WPVI has its studios located on the border between Philadelphia and Bala Cynwyd, and its transmitter is located in the...
, the ABC O&OOwned-and-operated stationIn the broadcasting industry , an owned-and-operated station usually refers to a television station or radio station that is owned by the network with which it is associated...
in Philadelphia, simulcasts two channels in 720p HD (the regular WPVI/ABC schedule and Live Well HD NetworkLive Well HD NetworkLive Well Network is a home, health and lifestyle high definition digital subchannel network owned by Disney-ABC Television Group. The network launched as Live Well HD Network on April 27, 2009, and is currently available on digital subchannels of all ABC owned and operated stations and Belo...
, respectively), and then WPVI's "ABC Plus"/Local AccuWeatherThe Local AccuWeather ChannelThe Local AccuWeather Channel is a 24-hour, weather-oriented, commercially sponsored broadcast and cable television network in the United States owned and operated by AccuWeather, Inc., which is headquartered in State College, Pennsylvania....
in 480i standard definition. WPVI is also one of the few stations broadcasting digital television in the VHF spectrum (channels 2 to 6) below the FM radio band. Other ABC-owned stations also have the same ABC/Live Well/ABC Plus-Local AccuWeather channel map setup as well, though a few have Live Well and ABC Plus-Local AccuWeather airing in regular 480i.
Outside of the United States, especially in Europe, high-definition feeds are rarer, and most countries only provide a single high-definition service for each broadcaster. For example, digital television in France
Télévision Numérique Terrestre
TNT is the national digital terrestrial service for France. It formally arrived on 31 March 2005 after a short testing period. Like Freeview in the United Kingdom it will support many new channels as well as the current terrestrial television stations...
only has five HD services, one each for TF1
TF1
TF1 is a national French TV channel, controlled by TF1 Group, whose major share-holder is Bouygues. TF1's average market share of 24% makes it the most popular domestic network...
, France 2
France 2
France 2 is a French public national television channel. It is part of the state-owned France Télévisions group, along with France 3, France 4, France 5 and France Ô...
, Canal+
Canal+
Canal+ is a French premium pay television channel launched in 1984. It is 80% owned by the Canal+ Group, which in turn is owned by Vivendi SA. The channel broadcasts several kinds of programming, mostly encrypted...
, M6 and Arte
Arte
Arte is a Franco-German TV network. It is a European culture channel and aims to promote quality programming especially in areas of culture and the arts...
, and the United Kingdom is currently broadcasting four HD services over terrestrial frequencies including BBC One HD, BBC HD
BBC HD
BBC HD is a high-definition television network provided by the BBC. The service was initially run as a trial from 15 May 2006 until becoming a full service on 1 December 2007...
, ITV1 HD, and Channel 4 HD (S4C Clirlun is broadcast in Wales instead of Channel 4 HD).
Educational programming
Many Public Broadcasting ServicePublic 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....
(PBS) stations around the United States broadcast four SD channels during the daytime, and one HD and one SD channel at night. PBS stations often carry additional national channels such as PBS HD (PBS Satellite Service), PBS Kids Sprout
PBS KIDS Sprout
PBS Kids Sprout is a U.S. digital cable television channel, video-on-demand service, and website providing PBS Kids shows and original programming for preschoolers and their families...
, PBS World
PBS World
PBS World is a 24-hour United States over-the-air digital subchannel showing public TV non-fiction, science, nature, news, public affairs and documentaries...
, Create, PBS Learner (The Annenberg Channel
Annenberg Foundation
The Annenberg Foundation is a private foundation that provides funding and support to non-profit organizations in the United States and around the world...
) or the Spanish-language V-me
V-me
V-me is a public television service in the United States, broadcasting only in Spanish. The 24-hour digital broadcast service was launched on March 5, 2007, and is currently available in over 75% of all U.S...
network. MHz Networks
MHz Networks
MHz Networks is a Northern Virginia based independent, non-commercial educational broadcaster operated by Commonwealth Public Broadcasting Corporation. The legal broadcast callsigns for the two stations of MHz Networks are WNVC and WNVT...
transmits to the Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
area on ten subchannels transmitted by two stations, with 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....
numbering making them appear as one station.
In some US states, state-wide educational, cultural or public-affairs
Public affairs (broadcasting)
Public affairs, a broadcasting industry term, refers to television programs which focuses on matters of politics and public policy. Among commercial broadcasters, such programs are often only to satisfy Federal Communications Commission regulatory expectations and are not scheduled in prime time...
services are carried by existing PBS member stations on digital subchannels; these include regional services such as the Minnesota Channel
Minnesota Channel
The Minnesota Channel is a full-time state-wide network originating at Twin Cities Public Television. It is carried on digital subchannels of nine stations and features programming related to Minnesota , plus coverage of the Minnesota Legislature when in session.- History :In early 2003, TPT began...
, Wisconsin Channel or New York State broadcaster ThinkBright TV. The use of subchannels has also allowed educational television
Educational television
Educational television is the use of television programs in the field of distance education. It may be in the form of individual television programs or dedicated specialty channels that is often associated with cable television in the United States as Public, educational, and government access ...
broadcasters to sell off former secondary PBS analogue stations (such as WNEQ in Buffalo
Buffalo, New York
Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...
to LIN TV
LIN TV
LIN TV Corporation is an American holding company that operates 31 television stations.-History:LIN TV's roots trace back to the founding of its former parent, LIN Broadcasting Corporation, in 1961. LIN Broadcasting was engaged in radio, television, direct marketing, information and learning, music...
to become CW affiliate WNLO
WNLO
WNLO is the CW-affiliated television station for Western New York licensed to Buffalo. It broadcasts a high definition digital signal on UHF channel 32 from a transmitter on the eastern side of Grand Island. The station can also be seen on Time Warner Cable channel 11 and Verizon FiOS channel 23...
) to commercial broadcasters
Commercial broadcasting
Commercial broadcasting is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship...
, as the additional educational content these once provided can now be carried by multiple subchannels of the one main station. Subchannels also allow stations to devote an entire channel to telecourses
Distance education
Distance education or distance learning is a field of education that focuses on teaching methods and technology with the aim of delivering teaching, often on an individual basis, to students who are not physically present in a traditional educational setting such as a classroom...
which are recorded by instructors and students for later use, freeing the original channel to air a more general schedule in the morning and overnight hours
Graveyard slot
A graveyard slot is a time period in which a television audience is very small compared to other times of the day, and therefore broadcast programming is considered far less important. Graveyard slots are usually in the early morning hours of each day, when most people are asleep...
.
Commercial networks
In small media marketMedia market
A media market, broadcast market, media region, designated market area , Television Market Area , or simply market is a region where the population can receive the same television and radio station offerings, and may also include other types of media including newspapers and Internet content...
s in the United States, one or more national networks are unavailable from local over-the-air
Over-the-air
Over-the-air has several meanings, depending on context. *Generally, over-the-air is synonymous for wireless.*Specifically, over-the-air can have the following meanings or is used in the following contexts:...
sources. A small city with only one or two commercial stations would not be able to carry the full programming lineup from all four largest commercial networks (CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
, NBC
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
, ABC
American Broadcasting Company
The American Broadcasting Company is an American commercial broadcasting television network. Created in 1943 from the former NBC Blue radio network, ABC is owned by The Walt Disney Company and is part of Disney-ABC Television Group. Its first broadcast on television was in 1948...
, 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...
) in analogue as one station could only broadcast one program at a time. This limitation could be overcome by adding the additional networks as digital subchannels of existing local commercial stations. One prime example of this is in the Wheeling, West Virginia
Wheeling, West Virginia
Wheeling is a city in Ohio and Marshall counties in the U.S. state of West Virginia; it is the county seat of Ohio County. Wheeling is the principal city of the Wheeling Metropolitan Statistical Area...
/Steubenville, Ohio
Steubenville, Ohio
Steubenville is a city located along the Ohio River in Jefferson County, Ohio on the Ohio-West Virginia border in the United States. It is the political county seat of Jefferson County. It is also a principal city of the Weirton–Steubenville, WV-OH Metropolitan Statistical Area...
market, which for decades has had only two television stations (CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
affiliate WTRF-TV
WTRF-TV
WTRF-TV is the CBS-affiliated television station for the Northern Panhandle of West Virginia and the Allegheny Plateau of Eastern Ohio that is licensed to Wheeling, West Virginia. It broadcasts a high definition digital signal on VHF channel 7 from a transmitter in Bridgeport, Ohio. Owned by West...
and NBC
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
affiliate WTOV-TV
WTOV-TV
WTOV-TV is the NBC-affiliated television station for the Ohio Valley that is licensed to Steubenville & Wheeling. It broadcasts a high definition digital signal on VHF channel 9 from a transmitter in Mingo Junction, Ohio. Owned by Cox Enterprises, the station has studios in Steubenville. Syndicated...
, as well as cable-only CW affiliate WBWO
The CW Plus
The CW Plus is a group of primarily digital sub-channels, analog, and non-broadcast cable television outlets for the CW Television Network, for markets below the top 99 television media markets in the United States....
) and had to mostly rely on stations in Pittsburgh (and to a lesser extent Columbus
Columbus, Ohio
Columbus is the capital of and the largest city in the U.S. state of Ohio. The broader metropolitan area encompasses several counties and is the third largest in Ohio behind those of Cleveland and Cincinnati. Columbus is the third largest city in the American Midwest, and the fifteenth largest city...
and Youngstown, Ohio
Youngstown, Ohio
Youngstown is a city in the U.S. state of Ohio and the county seat of Mahoning County; it also extends into Trumbull County. The municipality is situated on the Mahoning River, approximately southeast of Cleveland and northwest of Pittsburgh, Pennsylvania...
) for other networks. However, the advent of digital television has allowed WTRF to launch two digital channels (one for Fox with MyNetworkTV as a secondary affiliate, the other for ABC) while still airing the full CBS schedule on its main signal.
Digital subchannels also help expand the traditional coverage areas of a station beyond their former analog boundaries. In the Upper Peninsula of Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
and northern Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
, many of those stations are on duplicate frequencies to cover a large market area. This is used to duplicate network service for stations which are part of duopolies
Duopoly (broadcasting)
In United States broadcast television and radio, duopoly is a term used to describe a single company which owns two or more stations in the same city or community....
, where transmitters scattered through a large geographical area allow multiple networks and channels to be carried.
The most prominent example is Duluth, Minnesota
Duluth, Minnesota
Duluth is a port city in the U.S. state of Minnesota and is the county seat of Saint Louis County. The fourth largest city in Minnesota, Duluth had a total population of 86,265 in the 2010 census. Duluth is also the second largest city that is located on Lake Superior after Thunder Bay, Ontario,...
's Northland's NewsCenter
Northland's NewsCenter
The Northland's NewsCenter, began in 2005 but not completed until early 2006, is a collective name for news for the Duluth, Minnesota area's NBC, CBS, MyNetworkTV and The CW stations all operated or owned by Granite Broadcasting. It was originated from KBJR-TV's newscasts but now provides content...
quadopoly of stations from Granite Broadcasting, which consists of two traditional broadcasters, NBC station KBJR
KBJR-TV
KBJR-TV is the NBC-affiliated television station for Northeastern Minnesota and Northwestern Wisconsin that is licensed to Superior, Wisconsin. It broadcasts a high definition digital signal on UHF channel 19 from a transmitter west of Downtown Duluth in Hilltop Park...
and CBS affiliate KDLH
KDLH
KDLH is the CBS-affiliated television station for the Iron Range area of Northeastern Minnesota that is licensed to Duluth. It broadcasts a high definition digital signal on UHF channel 33 from a transmitter west of downtown in Hilltop Park. Owned by the Malara Broadcast Group, the station is...
, and three subchannels, CW Plus affiliate Northland CW 2
KDLH-DT2
KDLH-DT2 is the CW-affiliated television station for the Iron Range of Northeastern Minnesota. The station is part of The CW Plus, a special CW feed that broadcasts on cable and/or over-the-air on a digital signal...
, My9
KBJR-DT2
KBJR-DT2 is the MyNetworkTV-affiliated television station for the Iron Range of northeastern Minnesota. The station is a second digital subchannel of NBC affiliate KBJR which is owned by the Granite Broadcasting Corporation. Over-the-air, it broadcasts a digital signal on UHF channel 19.2 from...
, the area's MyNetworkTV station, and a local weather station. While KDLH carries CW2 on their DT2 signal and My9 airs on KBJR-DT2 on their traditional Duluth signal, all five channels are carried on Chisholm
Chisholm, Minnesota
As of the census of 2000, there were 4,960 people, 2,178 households, and 1,287 families residing in the city. The population density was 1,129 people per square mile . There were 2,375 housing units at an average density of 540/sq mi...
-based sister station KRII to the north for the Iron Range
Iron Range
The Iron Range is a region that makes up the northeastern section of Minnesota in the United States. "The Range", as it is known by locals, is a region with multiple distinct bands of iron ore...
region, providing that area stations which were previously unavailable over-the-air.
This is also the case with Upper Michigan station WPBN/WTOM
WPBN-TV
WPBN-TV is the NBC-affiliated television station for the Northern Lower and Eastern Upper Peninsulas of Michigan that is licensed to Traverse City. It broadcasts a high definition digital signal on UHF channel 47 from a transmitter east of Kalkaska...
, which also airs the signals of sister station WGTU/WGTQ
WGTU
WGTU is the ABC-affiliated television station for the Northern Lower and Eastern Upper Peninsulas of Michigan that is licensed to Traverse City. It broadcasts a high definition digital signal on UHF channel 29 from a transmitter east of Kalkaska. Like other network affiliates in this vast rural...
, providing WGTU/WGTQ's ABC programming across a wider coverage area, while WWTV/WWUP
WWTV
WWTV is the CBS-affiliated television station for the northern Lower and eastern Upper Peninsulas of Michigan. Licensed to Cadillac, it broadcasts a high definition digital signal on VHF channel 9 from a transmitter at its studios on 130th Avenue, northeast of Tustin, in Osceola County. At 1,631...
carries their sister Fox station WFQX
WFQX-TV
WFQX-TV is the Fox-affiliated television station for the northern Lower and eastern Upper Peninsulas of Michigan. Licensed to Cadillac, it broadcasts a high definition digital signal on UHF channel 32 from a transmitter at studios on 130th Avenue/Dighton Road in Tustin on Grove Hill...
on their DT2 subchannel to expand their coverage area further north into the eastern portion of the Upper Peninsula.
In many cases, these "new" channels are existing secondary channels which were carried by a low-power or Class A station
Class A television service
The class A television service is a system for regulating some low-power television stations in the United States. Class A stations are denoted by the broadcast callsign suffix "-CA" or "-CD" , although very many analog -CA stations have a digital companion channel that was assigned the -LD...
or by a 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...
channel. Often, a full-power TV station acquires or already owns a low-power secondary station in the same market to carry a second network. The use of a digital subchannel on a full power TV station as a replacement for LPTV greatly increases coverage areas for this programming.
With the launches of The CW
The CW Television Network
The CW Television Network is a television network in the United States launched at the beginning of the 2006–2007 television season. It is a joint venture between CBS Corporation, the former owners of United Paramount Network , and Time Warner's Warner Bros., former majority owner of The WB...
and MyNetworkTV
MyNetworkTV
MyNetworkTV is a television broadcast syndication service in the United States, owned by the Fox Entertainment Group, a division of News Corporation...
, many television stations have been launching subchannels affiliating with these secondary networks.
Because of the nature of transmissions in the low VHF band (channels 2 through 6), some stations using these frequencies are relayed on the subchannels of stations that use more advantageous frequencies. An example of this is WRGB
WRGB
WRGB, channel 6, is a television station located in Schenectady, New York, USA. WRGB is owned by Freedom Communications, and is the CBS affiliate for the Albany-Schenectady-Troy television market...
, the CBS affiliate of Albany, New York
Albany, New York
Albany is the capital city of the U.S. state of New York, the seat of Albany County, and the central city of New York's Capital District. Roughly north of New York City, Albany sits on the west bank of the Hudson River, about south of its confluence with the Mohawk River...
. While WRGB broadcasts in high-definition on channel 6, a standard-definition feed of WRGB can also be seen as a subchannel of CW affiliate (and duopoly
Duopoly (broadcasting)
In United States broadcast television and radio, duopoly is a term used to describe a single company which owns two or more stations in the same city or community....
partner) WCWN
WCWN
WCWN is the CW-affiliated television station for New York State's Capital District and Western New England. Licensed to Schenectady, New York, it broadcasts a high definition digital signal on UHF channel 43 from a transmitter southwest of New Scotland's Voorheesville section...
, on channel 45.
Other stations have launched separate independent station
Independent station
An independent station is in the category of television terminology used to describe a television station broadcasting in the United States or Canada that is not affiliated with any television network....
s on their DT-2 signals.
Sports programming
Networks dedicated to sports programming (such as Universal SportsUniversal Sports
Universal Sports is an American television network that airs various sports, primarily those contested in the Olympic Games, including swimming, gymnastics, cycling, track and field, figure skating, skiing, bobsledding and triathlon.-Programming:...
and Untamed Sports TV
Untamed Sports TV
Untamed Sports TV is a digital subchannel which provides niche outdoor and lifestyle programming to several stations in the United States. This channel was launched in 2008 by OlympuSAT who also distributes the Funimation Channel.-Programs:...
) have been launched for TV stations digital subchannels. A common use for digital subchannels is for CBS
CBS
CBS Broadcasting Inc. is a major US commercial broadcasting television network, which started as a radio network. The name is derived from the initials of the network's former name, Columbia Broadcasting System. The network is sometimes referred to as the "Eye Network" in reference to the shape of...
affiliates to show all of the early round games of the NCAA Basketball Tournament
NCAA Men's Division I Basketball Championship
The NCAA Men's Division I Basketball Championship is a single-elimination tournament held each spring in the United States, featuring 68 college basketball teams, to determine the national championship in the top tier of college basketball...
on their digital channel, which is subdivided into four different subchannels. (Most of the major professional sports leagues, however, have strict prohibitions against this and only allow one game to be aired in a market at one time; all four of the major leagues have out-of-market sports package
Out-of-Market Sports Package
In the North America, an Out-of-Market Sports Package is a form of subscription television that broadcasts sporting events to areas who are unavailable to see them because the games are not broadcast in their local market....
s that require a paid subscription and generate significant revenue for the leagues.)
Local and informational channels
Many local broadcasters are using subchannels to carry continuous news or local weather; secondary networks such as AccuWeather ChannelThe Local AccuWeather Channel
The Local AccuWeather Channel is a 24-hour, weather-oriented, commercially sponsored broadcast and cable television network in the United States owned and operated by AccuWeather, Inc., which is headquartered in State College, Pennsylvania....
have been created to serve this audience.
Specialty programming
Networks dedicated to re-running TV shows and movies (such as Retro Television, This TVThis TV
This TV is a United States general entertainment television network, with a large emphasis in its programming on movies....
and .2 Network
.2 Network
.2 Network was the name of a planned television network designed for digital television subchannels owned by Guardian Enterprise Group that will replace the GTN network on a date never announced....
) have been launched for TV stations digital subchannels. Some TV stations (such as K38IZ-D in Phoenix, Arizona
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
) broadcast classic TV shows and music video
Music video
A music video or song video is a short film integrating a song and imagery, produced for promotional or artistic purposes. Modern music videos are primarily made and used as a marketing device intended to promote the sale of music recordings...
s on their digital subchannels. Music-video formats have also been tried as digital subchannels on terrestrial stations.
Spanish programming
Networks dedicated to Spanish programming (such as Estrella TVEstrella TV
Estrella TV is a Spanish-language television network owned by Liberman Broadcasting. The network launched September 14, 2009.-Affiliates:-Former Affiliates:-Controversy:...
and Mexicanal
Mexicanal
Mexicanal Network is a Mexican based television Network launched in 2005 by and and serves Mexicans living and working in the United States, Canada and Mexico....
) have been launched for TV stations digital subchannels.
Temporary installations
A digital subchannel can be used to restore service from a station which has been knocked off-the-air due to an antenna tower collapse; the affected signal would be made available in standard-definition, or even compressed high definition, on a subchannel of another local broadcaster, most often a competitor. KATVKATV
KATV, channel 7, is an ABC affiliated television station serving the Little Rock television market and central Arkansas. The station is owned by Allbritton Communications Company....
(ABC, Little Rock) was forced to follow this path in 2008, moving its digital signal to a subchannel of local MyNetworkTV
MyNetworkTV
MyNetworkTV is a television broadcast syndication service in the United States, owned by the Fox Entertainment Group, a division of News Corporation...
affiliate KWBF after a tower collapse
KATV Tower
The KATV tower was a 2000 ft tall television mast built near Redfield, Arkansas in 1965 at . Its Federal Communications Commission registration and other sources claim that it was built in 1967, but they are incorrect; the Clear Channel Broadcasting Tower Redfield also has an incorrect...
knocked its main signal off-air. The 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....
numbering scheme allows an existing licensed broadcaster to keep its displayed channel number unchanged (KATV ABC 7 in this case) even if the signal is carried physically as a subchannel of some other local station.
During the Station Fire in 2009, Los Angeles station KNBC
KNBC
KNBC, channel 4, is an owned-and-operated television station of the NBC Television Network, licensed to Los Angeles, California, USA. KNBC's studios and offices are located within the NBC Studios complex in Burbank, California, and its transmitter is located on Mount Wilson...
temporarily replaced NBC Plus and Universal Sports
Universal Sports
Universal Sports is an American television network that airs various sports, primarily those contested in the Olympic Games, including swimming, gymnastics, cycling, track and field, figure skating, skiing, bobsledding and triathlon.-Programming:...
on its subchannels with standard-definition feeds from sister stations KWHY-TV
KWHY-TV
KWHY-TV, channel 22, is a Spanish-language independent station located in Los Angeles, California, USA. KWHY-TV is owned by the Meruelo Group, a Los Angeles-based real estate and investment firm. The station's transmitter is on Mount Wilson.-History:...
(independent) and KVEA
KVEA
KVEA is a Spanish-language television station in the Los Angeles area owned and operated by NBC Universal and the West Coast flagship station of the Telemundo network. It was the first mainland U.S. station owned by Telemundo at the network's launch in the late 1980's...
(Telemundo) as an emergency measure in the event those stations' transmitters were destroyed or disabled as the fire reached the Mount Wilson
Mount Wilson
Mount Wilson can refer to several things:* Mount Wilson ** Mount Wilson Observatory* Mount Wilson, New South Wales, a mountain with a small hamlet in Australia* One of a list of peaks named Mount Wilson...
transmitter site for most Los Angeles area stations.
Data, radio and non-public signals
In rare cases, digital TV broadcasters have included the audio of a commonly-ownedDuopoly (broadcasting)
In United States broadcast television and radio, duopoly is a term used to describe a single company which owns two or more stations in the same city or community....
broadcast radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
among their subchannel offerings (for instance, KCSM-TV
KCSM-TV
KCSM-TV, virtual channel 60, is an independent, non-commercial television station located in San Mateo, California, USA. Until 2009, KCSM-TV was a PBS member station...
in San Mateo, California
San Mateo, California
San Mateo is a city in San Mateo County, California, United States, in the San Francisco Bay Area. With a population of approximately 100,000 , it is one of the larger suburbs on the San Francisco Peninsula, located between Burlingame to the north, Foster City to the east, Belmont to the south,...
broadcasts KCSM FM on its DT3 signal). WANN-LD in Atlanta
Atlanta, Georgia
Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...
offers six radio stations owned by Clear Channel Communications
Clear Channel Communications
Clear Channel Communications, Inc. is an American media conglomerate company headquartered in San Antonio, Texas. It was founded in 1972 by Lowry Mays and Red McCombs, and was taken private by Bain Capital LLC and Thomas H. Lee Partners LP in a leveraged buyout in 2008...
, in addition to ten TV channels. This type of service is known as DTV radio.
Non-broadcast content, subscription TV channels or datacasting
Datacasting
Datacasting is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital television, but may also be applied to digital signals on analog TV or radio...
operations unrelated to the main TV programming are also permitted by the DTV standards but are less-commonly used. USDTV
USDTV
USDTV, an acronym for U.S. Digital Television, was an over-the-air, pay television service in the United States. Based in Draper, Utah near Salt Lake City, it was founded in 2003 and started service there in 2004...
was an over-the-air pay TV
Pay TV
Pay television, premium television, or premium channels refers to subscription-based television services, usually provided by both analog and digital cable and satellite, but also increasingly via digital terrestrial and internet television...
service that used H.264 compression instead of standard MPEG-2
MPEG-2
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
. Mobile DTV now uses MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
compression, which like H.264 yields a much lower bitrate
Bitrate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
for the same video quality
Video quality
Video quality is a characteristic of a video passed through a video transmission/processing system, a formal or informal measure of perceived video degradation...
. For example, the Sezmi TV/DVR service uses broadcast digital sub-channels (not in the clear) in selected cities to stream a limited number of "cable" channels to its subscribers for an additional fee to supplement its otherwise free 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) service allowing recordings of local broadcast channels and free and subscription internet content.
Technical considerations
Digital television supports multiple digital subchannels if the approximately 19.4Mb/s (megabits per second) bitstreamBitstream
A bitstream or bit stream is a time series of bits.A bytestream is a series of bytes, typically of 8 bits each, and can be regarded as a special case of a bitstream....
is divided. Therefore, station managers and broadcast engineers could run any of the following scenarios using one 6 MHz channel (note that the actual bitrate moves up and down, due to usage of variable bitrate
Variable bitrate
Variable bitrate is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate , VBR files vary the amount of output data per time segment...
encoding):
| HDTV channels | Subchannels | ||
|---|---|---|---|
| 1× 1080i or 720p HDTV (19 Mbit/s) | No additional subchannels, unless HD is transmitted at 15Mbit/s or less. | ||
| 1× 1080i or 720p HDTV (15 Mbit/s) | + 1 | 480p or 480i SD subchannel (~3.8 Mbit/s) | |
| 1× 1080i or 720p HDTV (11 Mbit/s) | + 1 | 720p HDTV (8 Mbit/s) subchannel | |
| 1× 1080i or 720p HDTV (11 Mbit/s) | + 2 | 480p or 480i SD subchannels (~3.8 Mbit/s each) | |
| 1× 720p HDTV channel (8 Mbit/s) | + 3 | 480p or 480i SD subchannels (~3.8 Mbit/s each) | |
| 2× 720p HDTV channels (9.6 Mbit/s each) | No SD subchannels | ||
| 2× 720p HDTV channels (7.8 Mbit/s each) | + 1 | 480p or 480i SD subchannel (~3.8 Mbit/s) | |
| No HDTV channels | + 2 | 480p or 480i SD subchannels (~6 Mbit/s each) | |
| No HDTV channels | + 3 | 480p or 480i SD subchannels (~6 Mbit/s each) | |
| No HDTV channels | + 4 | 480p or 480i SD subchannels (~4.2 Mbit/s each) | |
| No HDTV channels | + 5 | 480p or 480i SD subchannels (~3.8 Mbit/s each) | |
| No HDTV channels | + 6 | 480p or 480i SD subchannels (~3.1 Mbit/s each) | |
| No HDTV channels | + 7 | 480p or 480i SD subchannels (~2.7 Mbit/s each) | |
| No HDTV channels | + 8 | 480p or 480i SD subchannels (~2.4 Mbit/s each) | |
| No HDTV channels | + 9 | 480p or 480i SD subchannels (~2.1 Mbit/s each) | |
| No HDTV channels | + 10 | 480p or 480i SD subchannels (~1.9 Mbit/s each) | |
| No HDTV channels | +120 | mono radio subchannels (~0.2 Mbit/s each) | |
With improvements in MPEG encoding, and tighter VBR
VBR
VBR may refer to:* Variable bitrate, in telecommunications and computing, when the bitrate used in sound or video encoding is not held constant* Volume Boot Record, in computer disks, a type of boot sector that contains code for bootstrapping programs...
encoding, more subchannels can be combined. 1×720p + 4×480i is becoming more common.
For a 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...
of 30p
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 60i, uncompressed DTV channels have the following data rate
Data rate
Data rate can refer to:* Bit rate, or data transfer rate* Data signaling rate* Data rate units-See also:* Baud rate* Channel capacity* Throughput* Bandwidth everything in this page is falsified...
s in megapixels per second:
| 60 Hz | 50 Hz |
|---|---|
|
|
For ATSC
ATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
, these must be compressed into 19.4Mb/s total per physical 6 MHz RF
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...
channel over the air, and 38.8Mb/s for cable.
Digital radio
Various forms of digital radioDigital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...
also allow for multiple program streams.
See also
- In-band on-channelIn-band on-channelIn-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....
(IBOC), digital radio technology allowing digital subchannels on FM stationsFM broadcastingFM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"... - DABDigital audio broadcastingDigital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
and DVB, international digital radio-television standards in use in EuropeEuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area... - QAM tunerQAM tunerQAM stands for quadrature amplitude modulation, the format by which digital cable channels are encoded and transmitted via cable television providers...