# CMAudioSampleBufferCreateWithPacketDescriptions(allocator:dataBuffer:dataReady:makeDataReadyCallback:refcon:formatDescription:sampleCount:presentationTimeStamp:packetDescriptions:sampleBufferOut:) Creates a sample buffer with packet descriptions and a callback to make the data ready for use. ``` func CMAudioSampleBufferCreateWithPacketDescriptions(allocator: CFAllocator?, dataBuffer: CMBlockBuffer?, dataReady: Bool, makeDataReadyCallback: CMSampleBufferMakeDataReadyCallback?, refcon makeDataReadyRefcon: UnsafeMutableRawPointer?, formatDescription: CMFormatDescription, sampleCount numSamples: CMItemCount, presentationTimeStamp: CMTime, packetDescriptions: UnsafePointer?, sampleBufferOut: UnsafeMutablePointer) -> OSStatus ``` ## Parameters `allocator` The allocator to use for allocating the `CMSampleBuffer` object. Pass `kCFAllocatorDefault` to use the default allocator. `dataBuffer` `CMBlockBuffer` for the media data. This can be `NULL`, a `CMBlockBuffer` with no backing memory, a `CMBlockBuffer` with backing memory but no data yet, or a `CMBlockBuffer` that already contains the media data. If `CMBlockBuffer` contains the media data, `dataReady` should be `true`. `dataReady` Indicates whether or not the `BlockBuffer` already contains the media data. `makeDataReadyCallback` Callback that `CMSampleBufferMakeDataReady` should call to make the data ready. Can be `NULL`. `makeDataReadyRefcon` The reference constant, [`CMSampleBufferMakeDataReady(_:)`](/documentation/CoreMedia/CMSampleBufferMakeDataReady(_:)), that this function should pass to the callback. `formatDescription` A description of the media data’s format. Can’t be `NULL`. `numSamples` Number of samples in the `CMSampleBuffer`. Must not be 0. `presentationTimeStamp` Timestamp of the first sample in the buffer. Must be a numeric `CMTime`. `packetDescriptions` Array of `packetDescriptions`, one for each of `numSamples`. May be `NULL` if the samples are known to have a constant number of frames per packet and a constant size. `sampleBufferOut` On output, points to the newly created `CMSampleBuffer`. ## Return Value A result code. See [Sample Buffer Error Codes](/documentation/CoreMedia/sample-buffer-errors). ## Discussion Provides an optimization over `CMSampleBufferCreate`() when the caller already has `packetDescriptions` for the audio data. This routine uses the packetDescriptions to create the sizing and timing arrays required to make the sample buffer if necessary. ## Topics ### Callbacks [`CMSampleBufferMakeDataReadyCallback`](/documentation/CoreMedia/CMSampleBufferMakeDataReadyCallback) Client callback called by [`CMSampleBufferMakeDataReady(_:)`](/documentation/CoreMedia/CMSampleBufferMakeDataReady(_:)). --- 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)