---
title: assemblyTrackID
framework: avfoundation
role: symbol
role_heading: Instance Property
path: avfoundation/avassettrackplan/assemblytrackid
---

# assemblyTrackID

## Declaration

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

## Discussion

Discussion This is the track ID of this track when it is included in the assemblyComposition the planner passes to the completion handler to assemble all planned segments of all tracks into a single AVComposition. The assemblyTrackID serves the purpose as a unique identifier of the track in the incremental writing session. This does not necessarily match the trackID of the source asset. The client is responsible for remembering the relationship between assemblyTrackID and the trackID in the source asset.

## See Also

### Inspecting the track plan

- [mediaType](avfoundation/avassettrackplan/mediatype.md)
- [segmentConfigurations](avfoundation/avassettrackplan/segmentconfigurations.md)