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# CMFormatDescriptionEqualIgnoringExtensionKeys(_:otherFormatDescription:extensionKeysToIgnore:sampleDescriptionExtensionAtomKeysToIgnore:)

Returns a Boolean value that indicates whether two format descriptions are equal, ignoring differences in the extension keys you specify.

```
func CMFormatDescriptionEqualIgnoringExtensionKeys(_ formatDescription: CMFormatDescription?, otherFormatDescription: CMFormatDescription?, extensionKeysToIgnore formatDescriptionExtensionKeysToIgnore: CFTypeRef?, sampleDescriptionExtensionAtomKeysToIgnore: CFTypeRef?) -> Bool
```

## Parameters

`formatDescription`

The first description to compare.

`otherFormatDescription`

The second description to compare.

`formatDescriptionExtensionKeysToIgnore`

A single format description extension key (`CFString`) or an array (`CFArray`) of keys.

`sampleDescriptionExtensionAtomKeysToIgnore`

A single sample description extension atom key (four-character `CFString`) or an array (`CFArray`) of such keys.

## Return Value

<doc://com.apple.documentation/documentation/Swift/true> if the two descriptions are equal; otherwise, <doc://com.apple.documentation/documentation/Swift/false>.

## Discussion

When you specify any keys, the function ignores `kCMFormatDescriptionExtension_VerbatimSampleDescription` and `kCMFormatDescriptionExtension_VerbatimISOSampleEntry` for the purpose of comparison.

> Note:
> This function is `NULL` safe.

For extension atom keys, see [`kCMFormatDescriptionExtension_SampleDescriptionExtensionAtoms`](/documentation/CoreMedia/kCMFormatDescriptionExtension_SampleDescriptionExtensionAtoms).

---

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