---
title: passthroughTrackID
framework: avfoundation
role: symbol
role_heading: Instance Property
path: avfoundation/avvideocompositioninstructionprotocol/passthroughtrackid
---

# passthroughTrackID

An identifier of a source track to pass through without compositing.

## Declaration

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

## Discussion

Discussion If an instruction indicates to pass through a source frame without compositing, this property returns the corresponding track identifier. The compositor isn’t run for the duration of the instruction, and instead passes the source frame through to the output. The system automatically matches the required dimensions, clean aperture, and pixel aspect ratio values of the source buffer.

## See Also

### Getting track ID settings

- [requiredSourceTrackIDs](avfoundation/avvideocompositioninstructionprotocol/requiredsourcetrackids.md)
- [requiredSourceSampleDataTrackIDs](avfoundation/avvideocompositioninstructionprotocol/requiredsourcesampledatatrackids.md)