Second audio program
Encyclopedia
Second audio program also known as secondary audio programming, is an auxiliary
audio
channel
for analog television
that can be broadcast
or transmitted both over the air
and by cable TV.
to the acronym), or for the Descriptive Video Service
(DVS) offered in the U.S.
by PBS, along with broadcasting the local NOAA Weather Radio service or a local National Public Radio station at times where translation or DVS is not needed. SAP is used for broadcasting Canada's Parliamentary television channel CPAC in both English and French. SAP is also used for student radio station
s that cannot otherwise get on the air due to crowded FM broadcasting
bands.
, the multichannel television sound
standard 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
.
and SAP, travel on subcarrier
s of the video
carrier
, much like color for TV. It is not carried on the audio carrier like stereo 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 kHz, which is five times the 15.734 kHz 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 mono
audio which has been dbx
-encode
d for 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 on-location newscast
s as the foldback channel to reporters and cameramen. This channel is located at 6.5 times the pilot (102.271 kHz), and is also part of the MTS standard.
left and right main audio channels, and ATIS station ID, which is heard as Morse code
. On FM radio, radio reading service
s and other audio programs can be heard on subcarriers, however these are generally prohibited from public listening. On digital TV systems, selection is done through a menu as with analog TV, 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 TV stations.
Auxiliary
Auxiliary may refer to:* A backup site or system* Auxiliary input jack, generally for audio* Auxiliary verb* International auxiliary language* Auxiliary police* Auxiliaries, troops supporting the main force of an army** Auxiliaries...
audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
channel
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...
for analog television
Analog television
Analog television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal...
that can be broadcast
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
or transmitted both over the air
Terrestrial television
Terrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
and by cable TV.
Usage
It is often used for an alternate language (hence giving the facetious "Spanish audio program" expansionBackronym
A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....
to the acronym), or for the Descriptive Video Service
Descriptive Video Service
The Descriptive Video Service is a major United States producer of video description, which makes visual media, such as television programs, feature films, and home videos, more accessible to people who are blind or otherwise visually impaired...
(DVS) offered in the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
by PBS, along with broadcasting the local NOAA Weather Radio service or a local National Public Radio station at times where translation or DVS is not needed. SAP is used for broadcasting Canada's Parliamentary television channel CPAC in both English and French. SAP is also used for student 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...
s that cannot otherwise get on the air due to crowded FM broadcasting
FM broadcasting
FM 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"...
bands.
Standards
SAP is part of MTSMultichannel television sound
Multichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...
, the multichannel television sound
Multichannel television sound
Multichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...
standard set by the National Television Systems Committee (NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
) in 1984 in the United States. The NTSC video format and MTS are also used in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
.
Frequencies
MTS features, including stereoStereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
and SAP, travel on subcarrier
Subcarrier
A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...
s of the video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
carrier
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
, much like color for TV. It is not carried on the audio carrier like stereo for an FM radio broadcast however, as it only has a frequency deviation
Frequency deviation
Frequency deviation is used in FM radio to describe the maximum instantaneous difference between an FM modulated frequency and the nominal carrier frequency...
of ±25 kHz, whereas regular FM broadcasting has a deviation of ±75 kHz. The SAP subcarrier is located at 78.670 kHz, which is five times the 15.734 kHz MTS
Multichannel television sound
Multichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...
pilot signal
Pilot signal
In telecommunications, a pilot is a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes....
. In turn, the MTS pilot is locked to the horizontal sync frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of the video carrier for stability. The SAP channel contains mono
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
audio which has been dbx
Dbx (noise reduction)
dbx is a family of noise reduction systems developed by the company of the same name. The most common implementations are dbx Type I and dbx Type II for analog tape recording and, less commonly, vinyl LPs. A separate implementation, known as dbx-TV, is part of the MTS system used to provide stereo...
-encode
Encode
Encode may refer to:* Can be related to "Code"* Encode ApS, a Danish software company* Encode SA, a Greek information security company* ENCODE, the ENCyclopedia Of DNA Elements...
d for noise reduction, to improve the signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
. 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
Television station
A television station is a business, organisation or other such as an amateur television operator that transmits content over terrestrial television. A television transmission can be by analog television signals or, more recently, by digital television. Broadcast television systems standards are...
s can also broadcast a "PRO" (professional
Professional
A professional is a person who is paid to undertake a specialised set of tasks and to complete them for a fee. The traditional professions were doctors, lawyers, clergymen, and commissioned military officers. Today, the term is applied to estate agents, surveyors , environmental scientists,...
) audio subcarrier which is used to communicate with station personnel, particularly those engaged in electronic news gathering
Electronic news gathering
ENG is a broadcasting industry acronym which stands for electronic news gathering. It can mean anything from a lone broadcast journalist reporter taking a single professional video camera out to shoot a story, to an entire television crew taking a production truck or satellite truck on location...
. 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 on-location newscast
Remote broadcast
In broadcast engineering, a remote broadcast is broadcasting done from a location away from a formal television studio and is considered an electronic field production . A remote pickup unit is usually used to transmit the audio and/or video back to the television station, where it joins the...
s as the foldback channel to reporters 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 big-dish satellite TV 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 discreteDiscrete
Discrete in science is the opposite of continuous: something that is separate; distinct; individual.Discrete may refer to:*Discrete particle or quantum in physics, for example in quantum theory...
left and right main audio channels, and ATIS station ID, which is heard as Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
. On FM radio, radio reading service
Radio reading service
A radio reading service or reading service for the blind is a service of many universities, community groups and public radio stations, where a narrator reads books, newspapers and magazines aloud for the benefit of the blind and vision-impaired. It is most often carried on a subcarrier, with...
s and other audio programs can be heard on subcarriers, however these are generally prohibited from public listening. On digital TV systems, selection is done through a menu as with analog TV, 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
Digital subchannel
In broadcasting, digital subchannels are a means to transmit more than one independent program at the same time from the same digital radio or digital television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual...
s with an optional screen of title and artist information, however this prevents the viewer from watching the main video in the case of TV stations.