---
title: "CMTimebaseCopySourceTimebase(_:)"
framework: coremedia
role: symbol
role_heading: Function
path: "coremedia/cmtimebasecopysourcetimebase(_:)"
---

# CMTimebaseCopySourceTimebase(_:)

Returns the immediate source timebase of a timebase.

## Declaration

```swift
func CMTimebaseCopySourceTimebase(_ timebase: CMTimebase) -> CMTimebase?
```

## See Also

### Copying Timebases

- [CMTimebaseCopySource(_:)](coremedia/cmtimebasecopysource(_:).md)
- [CMTimebaseCopySourceClock(_:)](coremedia/cmtimebasecopysourceclock(_:).md)
- [CMTimebaseCopyUltimateSourceClock(_:)](coremedia/cmtimebasecopyultimatesourceclock(_:).md)