---
title: unusedTrackID()
framework: avfoundation
role: symbol
role_heading: Instance Method
path: avfoundation/avasset/unusedtrackid()
---

# unusedTrackID()

Returns an identifier that no other tracks in the asset use.

## Declaration

```swift
func unusedTrackID() -> CMPersistentTrackID
```

## Return Value

Return Value An unused CMPersistentTrackID value.