---
title: source
framework: coremedia
role: symbol
role_heading: Instance Property
path: coremedia/cmtimemapping/source
---

# source

A time range on the source timeline.

## Declaration

```swift
var source: CMTimeRange
```

## Discussion

Discussion For an empty edit, source.start is an invalid CMTime, in which case the system ignores source.duration. Otherwise, source.start is the starting time within the source, and source.duration is the duration of the source timeline to map to the target time range.

## See Also

### Accessing Time Ranges

- [target](coremedia/cmtimemapping/target.md)