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# Tween media

Store pairs of values to be interpolated between in QuickTime movies using tween media.

## Overview

> Important: Tween media is deprecated in the QuickTime file format. The information that follows documents existing content containing tween media and should not be used for new development.

Tween media is used to store pairs of values to be interpolated between in QuickTime movies. These interpolated values modify the playback of other media types by using track references and track input maps. For example, a tween media could generate gradually changing volume levels to cause a sound track to fade out. It has a media type of `'twen'`.

Every tween operation is based on a collection of one or more values from which a range of output values can be algorithmically derived. Each tween is assigned a time duration, and an output value can be generated for any time value within the duration. In the simplest kind of tween operation, a pair of values is provided as input and values between the two values are generated as output.

A tween track is a special track in a movie that is used exclusively as a modifier track. The data it contains, known as tween data, is used to generate values that modify the playback of other tracks, usually by interpolating values. The tween media handler sends these values to other media handlers; it never presents data.

## Topics

### Storing tween media

[Tween sample description](/documentation/QuickTime-File-Format/Tween_sample_description)

An atom that contains information for converting from media time to sample number to sample location for tweens.

[Tween sample data](/documentation/QuickTime-File-Format/Tween_sample_data)

[Tween type categories](/documentation/QuickTime-File-Format/Tween_type_categories)

[Tween QT atom container](/documentation/QuickTime-File-Format/Tween_QT_atom_container)

Specify the characteristics of a tween with atoms in a tween QT atom container.


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