---
title: "init(format:frameCapacity:initializingWith:)"
framework: avfaudio
role: symbol
role_heading: Initializer
path: "avfaudio/avreadonlyaudiopcmbuffer/init(format:framecapacity:initializingwith:)"
---

# init(format:frameCapacity:initializingWith:)

Creates a read-only buffer by allocating and initializing audio data via closure.

## Declaration

```swift
init(format: AVAudioFormat, frameCapacity: Int, initializingWith: (UnsafeMutablePointer<AudioBufferList>) throws -> Void) throws
```

## Parameters

- `format`: The audio format for the buffer.
- `frameCapacity`: The capacity in audio frames.
- `initializingWith`: Closure that receives the mutable AudioBufferList to initialize.

## Discussion

Discussion note: An error if allocation fails or the closure throws.

## See Also

### Creating a read-only buffer

- [init(copying:)](avfaudio/avreadonlyaudiopcmbuffer/init(copying:).md)
- [init(unsafeRetaining:)](avfaudio/avreadonlyaudiopcmbuffer/init(unsaferetaining:).md)