---
title: "init(forwardFlow:backwardFlow:)"
framework: videotoolbox
role: symbol
role_heading: Initializer
path: "videotoolbox/vtframeprocessoropticalflow/init(forwardflow:backwardflow:)"
---

# init(forwardFlow:backwardFlow:)

Creates an object with forward and backward optical flow pixel buffers.

## Declaration

```swift
init?(forwardFlow: CVPixelBuffer, backwardFlow: CVPixelBuffer)
```

## Parameters

- `forwardFlow`: A pixel buffer that contains forward optical flow. This value must be non-NULL and IOSurface backed.
- `backwardFlow`: A pixel buffer that contains backward optical flow. his value must be non-NULL and IOSurface backed.

## Discussion

Discussion Instances retain the buffers backing them. Returns NULL if a NULL CVPixelBuffer is provided or if CVPixelBuffers are not IOSurface backed.