What Is MTS and SAP?by Micah McDunnigan
If you have ever flipped your TV to your favorite station, only to hear the program in an entirely different language, it's because you accidentally pressed the "SAP" button. Secondary Audio Programming provides a way for non-English speakers or the visually impaired to enjoy regular TV shows. This alternative is made possible by using one of the multiple sound channels created by Multiple Television Sound, or MTS, technology.
Multichannel Television Sound
MTS technology allows multiple sound components within a television signal's audio. Each component is called a channel, which identifies itself to the TV's receiver. Audio systems originally used multiple channels to create stereo sound, with the sound from a particular channel serving as the source for a particular speaker. MTS technology enables stations to broadcast shows with support for a variety of home theater arrangements, as well as supplemental audio tracks for specific programs.
Secondary Audio Programming
The creation of multiple audio channels allows one of those channels to carry [SAP](https://itstillworks.com/12270038/what-is-sap) content. This audi content carries a description of the events unfolding on a show so the visually impaired can enjoy the programming or carry the program's dialogue in another language. Switch to hearing a program's SAP content by pressing the "SAP" button on your TV remote control. MTS is not a separate component you have to engage, rather it is a standard technology that is always available.
SAP content for a particular program is provided by the station that is broadcasting it. When the station does not provide a descriptive audio track to aid the visually impaired or record a separate version of its dialogue in another language, your TV will not find anything when you press the "SAP" button. If a station advertises SAP support for a particular program, but your TV is not producing anything when you press "SAP," contact your cable service provider to see if a technical issue is preventing the supplemental channel from reaching your home.
In 2009, television transmissions in the United States converted from analog signals to digital signals. The new standard allows your TV to receive more data from stations, such as eight audio channels. While this more robust format opens up greater technological possibilities, it also presented a challenge if you rely on SAP: as of this writing, television stations had not agreed which of those audio channels should carry SAP content. This lack of industry standard means that TV receivers cannot know which channel to use when you press "SAP." Until this issue is resolved, you may have trouble accessing a show's SAP content, even if the station is providing it.
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