The tuner interface is a uniform way to control inputs and outputs on a multi-input selection device. This is primarily used for input selection on elements for TV- and capture-cards.
Using this interface, it is possible to select one track from a list of tracks supported by that tuner-element. The tuner will than select that track for media-processing internally. This can, for example, be used to switch inputs on a TV-card (e.g. from Composite to S-video).
This interface is currently only implemented by the Video4linux and Video4linux2 elements.