---
title: "init(assetReaderTrackOutput:)"
framework: avfoundation
role: symbol
role_heading: Initializer
path: "avfoundation/avassetreaderoutputcaptionadaptor/init(assetreadertrackoutput:)"
---

# init(assetReaderTrackOutput:)

Creates a caption adaptor that reads from a track output.

## Declaration

```swift
init(assetReaderTrackOutput trackOutput: AVAssetReaderTrackOutput)
```

## Parameters

- `trackOutput`: The track output from which the system reads captions.