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# CMBlockBufferFlags

A type for flags that control behaviors and features of block buffer APIs.

```
typealias CMBlockBufferFlags = UInt32
```

## Topics

### Constants

[`kCMBlockBufferAssureMemoryNowFlag`](/documentation/CoreMedia/kCMBlockBufferAssureMemoryNowFlag)

When passed to routines that accept block allocators, causes the memory block to be allocated immediately.

[`kCMBlockBufferAlwaysCopyDataFlag`](/documentation/CoreMedia/kCMBlockBufferAlwaysCopyDataFlag)

Used with [`CMBlockBuffer`](/documentation/CoreMedia/CMBlockBuffer) to cause it to always produce an allocated copy of the desired data.

[`kCMBlockBufferDontOptimizeDepthFlag`](/documentation/CoreMedia/kCMBlockBufferDontOptimizeDepthFlag)

Passed to block buffers to suppress reference depth optimization.

[`kCMBlockBufferPermitEmptyReferenceFlag`](/documentation/CoreMedia/kCMBlockBufferPermitEmptyReferenceFlag)

Passed to [`CMBlockBuffer`](/documentation/CoreMedia/CMBlockBuffer) and [`CMBlockBuffer`](/documentation/CoreMedia/CMBlockBuffer) to allow references into a `CMBlockBuffer` that may not yet be populated.


---

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