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# VTSessionCopySupportedPropertyDictionary(_:supportedPropertyDictionaryOut:)

Retrieves a dictionary enumerating all the supported properties of a video toolbox session.

```
func VTSessionCopySupportedPropertyDictionary(_ session: VTSession, supportedPropertyDictionaryOut: UnsafeMutablePointer<CFDictionary?>) -> OSStatus
```

## Parameters

`session`

The session object.

`supportedPropertyDictionaryOut`

A pointer to a <doc://com.apple.documentation/documentation/CoreFoundation/CFDictionary>.

## Discussion

The keys of the returned dictionary are the supported property keys.

The values are themselves dictionaries, each containing the following optional fields:

- The type of value ([`kVTPropertyTypeKey`](/documentation/VideoToolbox/kVTPropertyTypeKey))
- The read/write status of the property ([`kVTPropertyReadWriteStatusKey`](/documentation/VideoToolbox/kVTPropertyReadWriteStatusKey))
- Whether the property is suitable for serialization ([`kVTPropertyShouldBeSerializedKey`](/documentation/VideoToolbox/kVTPropertyShouldBeSerializedKey))
- A range or list of the supported values, if appropriate
- Developer-level documentation for the property ([`kVTPropertyDocumentationKey`](/documentation/VideoToolbox/kVTPropertyDocumentationKey))

The caller must release the returned dictionary.

---

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