# kAudioUnitProperty_MatrixLevels Describes the internal state of a matrix mixer. ``` var kAudioUnitProperty_MatrixLevels: AudioUnitPropertyID { get } ``` ## Discussion Calculate the size required for this property’s value as follows: ```objc (input channel count + 1) * (output channel count + 1) ``` Obtain the channel counts using the `kAudioUnitProperty_MatrixDimensions` property. For example, consider a matrix mixer that has 2 input channels and 2 output channels. The value of this property then requires a 3 x 3 array of `Float32` values. You can retrieve specific pieces of information for this example matrix mixer’s state as follows: - Global volume is stored at `volumes[2][2]` - Input volumes are stored in the last column: first input channel at `volumes[0][2]`; second input channel at `volumes[1][2]` - Output volumes are stored in the last row: first output channel at `volumes [2][0]`; second output channel at `volumes[2][1]` - Cross-point volumes are stored at their expected locations(`volumes[0][1]`, etc) A read-only two-dimensional array of `Float32` values valid on the audio unit global scope. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)