---
title: sinkBufferUnderrunCount
framework: coremediaio
role: symbol
role_heading: Instance Property
path: coremediaio/cmioextensionstreamproperties/sinkbufferunderruncount-1qmbb
---

# sinkBufferUnderrunCount

The buffer underrun count.

## Declaration

```swift
@nonobjc var sinkBufferUnderrunCount: Int? { get set }
```

## Discussion

Discussion This value is a number the system increments whenever you’re not servicing buffers fast enough. This property translates to the kCMIOStreamPropertyOutputBufferUnderrunCount property.

## See Also

### Configuring Sink Properties

- [sinkBufferQueueSize](coremediaio/cmioextensionstreamproperties/sinkbufferqueuesize-9b80c.md)
- [sinkBuffersRequiredForStartup](coremediaio/cmioextensionstreamproperties/sinkbuffersrequiredforstartup-1bgyq.md)
- [sinkEndOfData](coremediaio/cmioextensionstreamproperties/sinkendofdata-8fswu.md)