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# mutableTrack(compatibleWith:)

Provides a reference to a track from a mutable movie into which you can insert any time range.

```
func mutableTrack(compatibleWith track: AVAssetTrack) -> AVMutableMovieTrack?
```

## Parameters

`track`

The [`AVAssetTrack`](/documentation/AVFoundation/AVAssetTrack) containing the desired time range.

## Return Value

An [`AVMutableMovieTrack`](/documentation/AVFoundation/AVMutableMovieTrack) object that can accommodate the time range insertion. Returns nil when no track is available.

## Discussion

Keep the number of tracks in a movie to a minimum, corresponding to the number of tracks for which media data must be presented in parallel. If media data of the same type is presented serially, even from multiple assets, a single track of that media type should be used. This method can help the client to identify an existing target track for an insertion.

---

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