# AudioFileGetUserDataSize(_:_:_:_:) Gets the size of a user data item in an audio file. ``` func AudioFileGetUserDataSize(_ inAudioFile: AudioFileID, _ inUserDataID: UInt32, _ inIndex: UInt32, _ outUserDataSize: UnsafeMutablePointer) -> OSStatus ``` ## Parameters `inAudioFile` The audio file whose user data item size you want. `inUserDataID` The four-character code of the designated user data item. `inIndex` An index of the user data item with the four-character code specified in `inUserDataID` that you want to query. `outUserDataSize` On output, if successful, the size of the user data item. ## Return Value A result code if there’s an error (see Result Codes) or `noErr` if the operation succeeds. ## Discussion In this function, *user data* refers to: - Chunks in AIFF, CAF, and WAVE files - Resources in Sound Designer II files - Other types of information in other files --- Copyright © 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)