---
title: trackID
framework: MediaExtension
role: symbol
role_heading: Instance Property
platforms: [macOS 14.0+]
path: mediaextension/metrackinfo/trackid
---

# trackID

An integer that identifies the track within the media asset.

## Declaration

```swift
var trackID: CMPersistentTrackID { get }
```

## Discussion

Discussion The track ID uniquely identifes the track within a MEFormatReader object. Track IDs must be unique within a media asset but don’t need to be unique across assets. If a media format doesn’t have a native concept of track IDs, track IDs can start from 1. However, track ID 0 is a reserved value to indicate an invalid track ID.

## See Also

### Inspecting track information

- [mediaType](mediaextension/metrackinfo/mediatype.md)
- [isEnabled](mediaextension/metrackinfo/isenabled.md)
- [naturalTimescale](mediaextension/metrackinfo/naturaltimescale.md)
- [extendedLanguageTag](mediaextension/metrackinfo/extendedlanguagetag.md)
- [naturalSize](mediaextension/metrackinfo/naturalsize.md)
- [preferredTransform](mediaextension/metrackinfo/preferredtransform.md)
- [nominalFrameRate](mediaextension/metrackinfo/nominalframerate.md)
- [requiresFrameReordering](mediaextension/metrackinfo/requiresframereordering.md)