# CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(_:bufferListSizeNeededOut:bufferListOut:bufferListSize:blockBufferAllocator:blockBufferMemoryAllocator:flags:blockBufferOut:) Returns an audio buffer list that contains the media data. ``` func CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(_ sbuf: CMSampleBuffer, bufferListSizeNeededOut: UnsafeMutablePointer?, bufferListOut: UnsafeMutablePointer?, bufferListSize: Int, blockBufferAllocator blockBufferStructureAllocator: CFAllocator?, blockBufferMemoryAllocator blockBufferBlockAllocator: CFAllocator?, flags: UInt32, blockBufferOut: UnsafeMutablePointer?) -> OSStatus ``` ## Parameters `sbuf` `CMSampleBuffer` being accessed. `bufferListSizeNeededOut` Receives the size of the AudioBufferList required to accommodate the data. May be `NULL`. `bufferListOut` Allocated by the caller, sized as specified by `bufferListSizeNeededOut`. It’s filled in with pointers into the retained `blockBufferOut`. May be `NULL`. `bufferListSize` Size of the `bufferListOut` allocated by the client. If `bufferListOut` isn’t `NULL` and `bufferListSize` is insufficient, `kFigSampleBufferError_ArrayTooSmall` is returned. `blockBufferStructureAllocator` Allocator to use when creating the `CMBlockBuffer` structure. `blockBufferBlockAllocator` Allocator to use for memory block held by the `CMBlockBuffer`. `flags` Flags controlling operation. `blockBufferOut` The retained `CMBlockBuffer`. ## Return Value A result code. See [Sample Buffer Error Codes](/documentation/CoreMedia/sample-buffer-errors). ## Discussion Creates an `AudioBufferList` containing the data from the `CMSampleBuffer`, and a `CMBlockBuffer` which references (and manages the lifetime of) the data in that `AudioBufferList`. The data may or may not be copied, depending on the contiguity and 16-byte alignment of the sample buffer’s data. The buffers placed in the `AudioBufferList` are guaranteed to be contiguous. The buffers in the `AudioBufferList` will be 16-byte-aligned if `kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment` is passed in. --- 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)