---
title: previousOpticalFlow
framework: videotoolbox
role: symbol
role_heading: Instance Property
path: videotoolbox/vtmotionblurparameters/previousopticalflow
---

# previousOpticalFlow

Optional optical flow object that contains forward and backward optical flow with the previous frame.

## Declaration

```swift
var previousOpticalFlow: VTFrameProcessorOpticalFlow? { get }
```

## Discussion

Discussion For the first frame this will always be nil. This object is only needed if optical flow is pre-computed.

## See Also

### Inspecting the parameters

- [sourceFrame](videotoolbox/vtmotionblurparameters/sourceframe.md)
- [nextFrame](videotoolbox/vtmotionblurparameters/nextframe.md)
- [previousFrame](videotoolbox/vtmotionblurparameters/previousframe.md)
- [motionBlurStrength](videotoolbox/vtmotionblurparameters/motionblurstrength.md)
- [nextOpticalFlow](videotoolbox/vtmotionblurparameters/nextopticalflow.md)
- [submissionMode](videotoolbox/vtmotionblurparameters/submissionmode-swift.property.md)
- [VTMotionBlurParameters.SubmissionMode](videotoolbox/vtmotionblurparameters/submissionmode-swift.enum.md)