<!--
{
  "availability" : [
    "iOS: 4.0.0 -",
    "iPadOS: 4.0.0 -",
    "macCatalyst: 13.1.0 -",
    "macOS: 10.7.0 -",
    "tvOS: 9.0.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 6.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "CoreMedia",
  "identifier" : "/documentation/CoreMedia/CMFormatDescriptionGetExtensions(_:)",
  "metadataVersion" : "0.1.0",
  "role" : "Function",
  "symbol" : {
    "kind" : "Function",
    "modules" : [
      "Core Media"
    ],
    "preciseIdentifier" : "c:@F@CMFormatDescriptionGetExtensions"
  },
  "title" : "CMFormatDescriptionGetExtensions(_:)"
}
-->

# CMFormatDescriptionGetExtensions(_:)

Returns all of the extensions for a format description.

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

## Parameters

`desc`

The `CMFormatDescription` to examine.

## Return Value

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

## 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.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)