---
title: streamSinkBufferUnderrunCount
framework: coremediaio
role: symbol
role_heading: Type Property
path: coremediaio/cmioextensionproperty/streamsinkbufferunderruncount
---

# streamSinkBufferUnderrunCount

A property key for the buffer underrun count.

## Declaration

```swift
static let streamSinkBufferUnderrunCount: CMIOExtensionProperty
```

## Discussion

Discussion The system updates this value every time you don’t service a stream’s buffer fast enough. The property state for property is a number with a read-only attribute. The value of this property matches the value of the kCMIOStreamPropertyOutputBufferUnderrunCount property.

## See Also

### Stream Properties

- [streamActiveFormatIndex](coremediaio/cmioextensionproperty/streamactiveformatindex.md)
- [streamFrameDuration](coremediaio/cmioextensionproperty/streamframeduration.md)
- [streamMaxFrameDuration](coremediaio/cmioextensionproperty/streammaxframeduration.md)
- [streamSinkBufferQueueSize](coremediaio/cmioextensionproperty/streamsinkbufferqueuesize.md)
- [streamSinkBuffersRequiredForStartup](coremediaio/cmioextensionproperty/streamsinkbuffersrequiredforstartup.md)
- [streamSinkEndOfData](coremediaio/cmioextensionproperty/streamsinkendofdata.md)