---
title: "CMFormatDescriptionGetExtensions(_:)"
framework: coremedia
role: symbol
role_heading: Function
path: "coremedia/cmformatdescriptiongetextensions(_:)"
---

# CMFormatDescriptionGetExtensions(_:)

Returns all of the extensions for a format description.

## Declaration

```swift
func CMFormatDescriptionGetExtensions(_ desc: CMFormatDescription) -> CFDictionary?
```

## Parameters

- `desc`: The CMFormatDescription to examine.

## Return Value

Return Value An immutable dictionary that contains all the extensions of the CMFormatDescription.  May be NULL.

## Discussion

Discussion If there are no extensions, the function returns NULL. Extensions dictionaries are valid property list objects.  This means that dictionary keys are all CFStrings, and the values are all either CFNumber, CFString, CFBoolean, CFArray, CFDictionary, CFDate, or CFData. The returned dictionary is not retained by this call, so clients are required to retain it if they need to keep it longer.

## See Also

### Inspecting Format Descriptions

- [CMFormatDescriptionGetMediaType(_:)](coremedia/cmformatdescriptiongetmediatype(_:).md)
- [CMFormatDescriptionGetMediaSubType(_:)](coremedia/cmformatdescriptiongetmediasubtype(_:).md)
- [CMFormatDescriptionGetExtension(_:extensionKey:)](coremedia/cmformatdescriptiongetextension(_:extensionkey:).md)
- [CMFormatDescriptionGetTypeID()](coremedia/cmformatdescriptiongettypeid().md)