---
title: "CMAudioFormatDescriptionCopyAsBigEndianSoundDescriptionBlockBuffer(allocator:audioFormatDescription:flavor:blockBufferOut:)"
framework: coremedia
role: symbol
role_heading: Function
path: "coremedia/cmaudioformatdescriptioncopyasbigendiansounddescriptionblockbuffer(allocator:audioformatdescription:flavor:blockbufferout:)"
---

# CMAudioFormatDescriptionCopyAsBigEndianSoundDescriptionBlockBuffer(allocator:audioFormatDescription:flavor:blockBufferOut:)

Copies the contents of an audio format description to a buffer in big-endian byte ordering.

## Declaration

```swift
func CMAudioFormatDescriptionCopyAsBigEndianSoundDescriptionBlockBuffer(allocator: CFAllocator?, audioFormatDescription: CMAudioFormatDescription, flavor: CMSoundDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer<CMBlockBuffer?>) -> OSStatus
```

## Parameters

- `allocator`: Allocator to use for allocating the CMBlockBuffer object. May be NULL.
- `audioFormatDescription`: CMAudioFormatDescription to be copied.
- `flavor`: kCMSoundDescriptionFlavor constant or NULL for QuickTimeMovie flavor.
- `blockBufferOut`: Receives new CMBlockBuffer containing SoundDescription data structure in big-endian byte ordering.

## Discussion

Discussion On return, the caller owns the returned CMBlockBuffer, and must release it when done with it. note: The dataRefIndex field of the SampleDescription is intentionally filled with placeholder values (0xFFFF). The caller must overwrite these values with a valid dataRefIndex if writing the SampleDescription to a QuickTime/ISO file.

## See Also

### Working with Audio Descriptions

- [CMSoundDescriptionFlavor](coremedia/cmsounddescriptionflavor.md)
- [CMAudioFormatDescriptionCreateSummary(allocator:formatDescriptionArray:flags:formatDescriptionOut:)](coremedia/cmaudioformatdescriptioncreatesummary(allocator:formatdescriptionarray:flags:formatdescriptionout:).md)
- [CMAudioFormatDescriptionCreate(allocator:asbd:layoutSize:layout:magicCookieSize:magicCookie:extensions:formatDescriptionOut:)](coremedia/cmaudioformatdescriptioncreate(allocator:asbd:layoutsize:layout:magiccookiesize:magiccookie:extensions:formatdescriptionout:).md)
- [CMAudioFormatDescriptionEqual(_:otherFormatDescription:equalityMask:equalityMaskOut:)](coremedia/cmaudioformatdescriptionequal(_:otherformatdescription:equalitymask:equalitymaskout:).md)
- [CMAudioFormatDescriptionGetChannelLayout(_:sizeOut:)](coremedia/cmaudioformatdescriptiongetchannellayout(_:sizeout:).md)
- [CMAudioFormatDescriptionGetFormatList(_:sizeOut:)](coremedia/cmaudioformatdescriptiongetformatlist(_:sizeout:).md)
- [CMAudioFormatDescriptionGetMagicCookie(_:sizeOut:)](coremedia/cmaudioformatdescriptiongetmagiccookie(_:sizeout:).md)
- [CMAudioFormatDescriptionGetMostCompatibleFormat(_:)](coremedia/cmaudioformatdescriptiongetmostcompatibleformat(_:).md)
- [CMAudioFormatDescriptionGetRichestDecodableFormat(_:)](coremedia/cmaudioformatdescriptiongetrichestdecodableformat(_:).md)
- [CMAudioFormatDescriptionGetStreamBasicDescription(_:)](coremedia/cmaudioformatdescriptiongetstreambasicdescription(_:).md)
- [CMDoesBigEndianSoundDescriptionRequireLegacyCBRSampleTableLayout(_:flavor:)](coremedia/cmdoesbigendiansounddescriptionrequirelegacycbrsampletablelayout(_:flavor:).md)
- [CMSwapBigEndianSoundDescriptionToHost(_:_:)](coremedia/cmswapbigendiansounddescriptiontohost(_:_:).md)
- [CMSwapHostEndianSoundDescriptionToBig(_:_:)](coremedia/cmswaphostendiansounddescriptiontobig(_:_:).md)
- [CMAudioFormatDescriptionCreateFromBigEndianSoundDescriptionData(allocator:bigEndianSoundDescriptionData:size:flavor:formatDescriptionOut:)](coremedia/cmaudioformatdescriptioncreatefrombigendiansounddescriptiondata(allocator:bigendiansounddescriptiondata:size:flavor:formatdescriptionout:).md)
- [CMAudioFormatDescriptionCreateFromBigEndianSoundDescriptionBlockBuffer(allocator:bigEndianSoundDescriptionBlockBuffer:flavor:formatDescriptionOut:)](coremedia/cmaudioformatdescriptioncreatefrombigendiansounddescriptionblockbuffer(allocator:bigendiansounddescriptionblockbuffer:flavor:formatdescriptionout:).md)