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# CMMetadataFormatDescriptionCreateWithMetadataFormatDescriptionAndMetadataSpecifications(allocator:sourceDescription:metadataSpecifications:formatDescriptionOut:)

Creates a metadata format description by extending an existing description with the values you specify.

```
func CMMetadataFormatDescriptionCreateWithMetadataFormatDescriptionAndMetadataSpecifications(allocator: CFAllocator?, sourceDescription: CMMetadataFormatDescription, metadataSpecifications: CFArray, formatDescriptionOut: UnsafeMutablePointer<CMMetadataFormatDescription?>) -> OSStatus
```

## Parameters

`allocator`

CFAllocator to be used. kCFAllocatorDefault if you don’t care.

`sourceDescription`

Source metadata format description being extended

`metadataSpecifications`

An array of dictionaries, each dictionary supplies a metadata identifier, a datatype, and an optional language tag.

`formatDescriptionOut`

Returned newly created metadata CMFormatDescription

## Discussion

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