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# init(propertiesOf:)

Creates a mutable video composition with the specified asset properties.

```
init(propertiesOf asset: AVAsset)
```

## Parameters

`asset`

An instance of [`AVAsset`](/documentation/AVFoundation/AVAsset). Ensure that the duration and tracks properties of the asset are already loaded before invoking this method.

## Discussion

The returned `AVMutableVideoComposition` has instructions that respect the spatial properties and time ranges of the specified asset’s video tracks.

It also has the following values for its properties:

- A value for [`frameDuration`](/documentation/AVFoundation/AVMutableVideoComposition/frameDuration) short enough to accommodate the greatest [`nominalFrameRate`](/documentation/AVFoundation/AVAssetTrack/nominalFrameRate) among the asset’s video tracks. If the [`nominalFrameRate`](/documentation/AVFoundation/AVAssetTrack/nominalFrameRate) of all of the asset’s video tracks is 0, a default frame rate of 30fps is used.
- If the specified asset is an instance of [`AVComposition`](/documentation/AVFoundation/AVComposition), the [`renderSize`](/documentation/AVFoundation/AVMutableVideoComposition/renderSize) is set to the [`naturalSize`](/documentation/AVFoundation/AVComposition/naturalSize) of the [`AVComposition`](/documentation/AVFoundation/AVComposition); otherwise the [`renderSize`](/documentation/AVFoundation/AVMutableVideoComposition/renderSize) will be set to a value that encompasses all of the asset’s video tracks.
- A [`renderScale`](/documentation/AVFoundation/AVMutableVideoComposition/renderScale) of 1.0.
- The [`animationTool`](/documentation/AVFoundation/AVMutableVideoComposition/animationTool) property set to `nil`.

---

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