---
title: "init(subBlockCapacity:blockSource:)"
framework: coremedia
role: symbol
role_heading: Initializer
path: "coremedia/cmmutabledatablockbuffer/init(subblockcapacity:blocksource:)"
---

# init(subBlockCapacity:blockSource:)

Creates a block buffer with at least subBlockCapacity number of sub blocks.

## Declaration

```swift
init(subBlockCapacity: Int, blockSource: CMMutableDataBlockBuffer.BlockSource? = nil)
```

## Parameters

- `subBlockCapacity`: Number of sub-blocks the new block buffer shall accommodate before expansion occurs. A value of zero means “do the reasonable default”.
- `blockSource`: Optional source to allocate and deallocate memory for the data blocks.