---
title: mAudioDataByteSize
framework: audiotoolbox
role: symbol
role_heading: Instance Property
path: audiotoolbox/audioqueuebuffer/maudiodatabytesize
---

# mAudioDataByteSize

The number of bytes of valid audio data in the audio queue buffer’s mAudioData field, initially set to 0. Your callback must set this value for a playback audio queue; for recording, the recording audio queue sets the value.

## Declaration

```swift
var mAudioDataByteSize: UInt32
```