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{{short description|Alternate audio channel used in television transmissions}}
{{About|an American analog television standard which is a part of MTS|the secondary audio feed on television in general|Sound multiplex in broadcasting}}
{{Use American English|date=December 2020}}
{{Use mdy dates|date=December 2020}}

'''Second audio program''' ('''SAP'''), also known as '''secondary audio programming''', is an auxiliary [[audio channel]] for [[analog television]] that can be [[Broadcasting|broadcast]] or transmitted both [[terrestrial television|over-the-air]] and by [[cable television]]. Used mostly for [[audio description]] or other languages, SAP is part of the [[multichannel television sound]] (MTS) standard originally set by the National Television Systems Committee ([[NTSC]]) in 1984 in the United States. The NTSC [[video format]] and MTS are also used in [[Canada]] and [[Mexico]].

==Usage==
SAP is often used to provide audio tracks in languages other than the native language included in the program. In the United States, this is sometimes used for [[Spanish language in the United States|Spanish-language]] audio (especially during sports telecasts), often leading to the function being referred to facetiously as the "Spanish audio program". Likewise, some Spanish-language programs may offer English on SAP, seen with [[association football|soccer]] networks including [[beIN Sports (American TV channel)|beIN Sports]] (which features the same setup on its English and Spanish channels, and more rarely with general channels. Some stations may relay [[NOAA Weather Radio]] services, or, particularly in the case of [[PBS]] stations, a local [[NPR|National Public Radio]] (NPR) sister station, on the audio channel when SAP is not being used, and even commercial radio stations which are either sister operations or [[brokered programming|broker their programming]] onto the SAP channel. In Canada, parliamentary and public affairs channel [[CPAC (TV channel)|CPAC]] similarly uses SAP to carry both English and [[Canadian French|French-language]] audio.

SAP is also a means of distribution for [[audio description]] of programs for the [[visually impaired]]. Under the [[Twenty-First Century Communications and Video Accessibility Act of 2010]], top U.S. television networks and cable networks have been gradually required to broadcast quotas of audio described programming per-quarter,<ref name="tvnc-launch">{{Cite web|url=https://tvnewscheck.com/article/60097/networks-set-to-launch-video-descriptions/|title=Networks Set To Launch Video Descriptions|date=2012-06-13|website=TVNewsCheck|language=en-US|access-date=2019-04-15}}</ref><ref name="lexology-dv">{{Cite web|url=https://www.lexology.com/library/detail.aspx?g=17b66353-ef69-4acb-b967-eb6385f242f6|title=FCC adopts video description regulations|last1=Browne|first1=Maria T.|last2=London|first2=Ronald G.|others=Davis Wright Tremaine LLP|website=Lexology|language=en|access-date=2019-04-15|last3=Holl|first3=Brendan}}</ref><ref>{{Cite web|url=https://www.broadcastingcable.com/news/fcc-expands-video-description-mandate-167092|title=FCC Expands Video Description Mandate|last=Eggerton|first=John|website=Broadcasting & Cable|language=en-us|access-date=2019-04-15}}</ref><ref>{{Cite web|url=https://money.cnn.com/2017/07/12/news/fcc-video-described-programming-blind-visually-impaired/index.html|title=FCC to require more shows be aired with video descriptions to aid the blind|last=Wattles|first=Jackie|date=2017-07-12|website=CNNMoney|access-date=2019-04-16}}</ref> Since May 26, 2015, broadcasters have been required under the Act to provide dictations on SAP of any "emergency information" displayed in a textual format outside of the [[Emergency Alert System]] and newscasts.<ref>{{Cite web|url=https://www.wileyrein.com/newsroom-articles-FCC_s_Text_to_Speech_Rule_Takes_Effect_November_30_2015.html|title=FCC's Text to Speech Rule Takes Effect November 30, 2015|publisher=Wiley Rein LLP|access-date=2019-04-16}}</ref><ref>{{Cite web|url=https://www.broadcastlawblog.com/2018/03/articles/fcc-requests-comments-on-extension-of-compliance-deadline-for-tv-stations-to-convert-non-textual-emergency-information-into-audio-on-sap-channel/|title=FCC Requests Comments on Extension of Compliance Deadline for TV Stations to Convert Non-Textual Emergency Information into Audio on SAP Channel|last=Oxenford|first=David|others=Wilkinson Barker Knauer LLP 1800 M. Street NW Suite 800N Washington DC 20036 Fax: 202.783.5851|date=2018-03-28|website=Broadcast Law Blog|language=en-US|access-date=2019-04-16}}</ref><ref>{{Cite web|url=https://www.commlawcenter.com/2018/05/fcc-grants-tv-stations-last-minute-reprieve-on-certain-audible-crawl-requirements.html|title=FCC Grants TV Stations Last-Minute Reprieve on Certain Audible Crawl Requirements|last=Kessler|first=Warren|date=2018-05-25|website=Comm Law Center|language=en-US|access-date=2019-04-16}}</ref>

==Frequencies==
MTS features, including [[stereophonic sound|stereo]] and SAP, travel on [[subcarrier]]s of the ''[[video]]'' [[carrier wave|carrier]], much like color for television. It is ''not'' carried on the audio carrier in the manner of stereo sound for an [[FM radio]] broadcast, however, as it only has a [[frequency deviation]] of ±25 kHz, whereas regular FM broadcasting has a deviation of ±75 kHz. The SAP subcarrier is located at 78.670 [[Kilohertz|kHz]], which is five times the 15.734 kHz corresponding to the [[Multichannel television sound|MTS]] [[pilot signal]]. In turn, the MTS pilot is locked to the [[horizontal sync]] [[frequency]] of the video carrier for stability. The SAP channel contains [[monoaural|mono]] audio which has been [[DBX (noise reduction)|dbx]]-[[Code|encode]]d for [[audio noise reduction|noise reduction]], to improve the [[signal-to-noise ratio]]. The SAP audio has a [[bandpass]] from 60 Hz to 12 kHz, which is less than the "regular" audio channel which runs from 50 Hz to 15 kHz.

Though not technically an SAP channel, [[television station]]s can also broadcast a "PRO" ([[professional]]) audio subcarrier which is used to communicate with station personnel, particularly those engaged in [[electronic news gathering]]. This one-way audio channel allows individuals at the television station to send messages to people located away from the station, and is frequently employed during [[remote broadcast|on-location newscast]]s as the [[interruptible foldback|foldback]] channel to [[reporter]]s and [[cameramen]]. This channel is located at 6.5 times the pilot (102.271 kHz), and is also part of the MTS standard.

==Other media==
Second audio programs are also available in other media. On analog [[television receive-only]] [[satellite television]] systems, audio programs are manually tuned by their subcarrier frequency, commonly around 6 MHz, often as low as 5.8 or as high as 7.2. These travel the same way as the [[:wikt:discrete|discrete]] left and right main audio channels, and [[Automatic Transmitter Identification System (television)|ATIS]] [[station identification|station ID]], which is heard as [[Morse code]]. On FM radio, [[radio reading service]]s and other audio programs can be heard on subcarriers through [[subsidiary communications authority]]; however, these are generally prohibited from public listening without special equipment. [[HD Radio]] subchannels, somewhat more widely available, operate on a similar premise but generally carry totally unrelated programming to the main feed.

On [[digital television]] systems, selection is done through a menu as with analog television, though some provide easier access rather than having to dig down to find the option. Stations may also choose to transmit audio-only programs by assigning them to separate [[digital subchannel]]s with an optional screen of title and artist information; however, this prevents the viewer from watching the main video in the case of television stations.

== References ==
{{Reflist}}
{{DEFAULTSORT:Second Audio Program}}
[[Category:Broadcast engineering]]
[[Category:Television technology]]
[[Category:Broadcasting]]

Second audio program - Revision history

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