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# kCVPixelBufferPoolFreeBufferNotification

A notification that the system posts if a buffer becomes available after it fails to create a pixel buffer with auxiliary attributes because it exceeded the threshold you specified.

```
let kCVPixelBufferPoolFreeBufferNotification: CFString
```

## Discussion

The system posts this notification if a buffer becomes available after the [`CVPixelBufferPoolCreatePixelBufferWithAuxAttributes(_:_:_:_:)`](/documentation/CoreVideo/CVPixelBufferPoolCreatePixelBufferWithAuxAttributes(_:_:_:_:)) function fails because the system exceeds the threshold you set for the [`kCVPixelBufferPoolAllocationThresholdKey`](/documentation/CoreVideo/kCVPixelBufferPoolAllocationThresholdKey) key. The system won’t post this notification if you don’t set a value for the [`kCVPixelBufferPoolAllocationThresholdKey`](/documentation/CoreVideo/kCVPixelBufferPoolAllocationThresholdKey) key for the `auxAttributes` parameter of the [`CVPixelBufferPoolCreatePixelBufferWithAuxAttributes(_:_:_:_:)`](/documentation/CoreVideo/CVPixelBufferPoolCreatePixelBufferWithAuxAttributes(_:_:_:_:)) function.

---

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