---
title: kVTCompressionPropertyKey_PixelAspectRatio
framework: videotoolbox
role: symbol
role_heading: Global Variable
path: videotoolbox/kvtcompressionpropertykey_pixelaspectratio
---

# kVTCompressionPropertyKey_PixelAspectRatio

The pixel aspect ratio for encoded frames.

## Declaration

```swift
let kVTCompressionPropertyKey_PixelAspectRatio: CFString
```

## Discussion

Discussion If a video encoder enforces specific pixel aspect ratios, this property will be read-only (VTSessionSetProperty(_:key:value:) returns kVTPropertyReadOnlyErr). The pixel aspect ratio is set on the format description for output samples, and may affect source frame scaling. NULL is a valid value for this property, meaning square pixels (1:1).

## See Also

### Clean Aperture and Pixel Aspect Ratio

- [kVTCompressionPropertyKey_AspectRatio16x9](videotoolbox/kvtcompressionpropertykey_aspectratio16x9.md)
- [kVTCompressionPropertyKey_CleanAperture](videotoolbox/kvtcompressionpropertykey_cleanaperture.md)
- [kVTCompressionPropertyKey_FieldCount](videotoolbox/kvtcompressionpropertykey_fieldcount.md)
- [kVTCompressionPropertyKey_FieldDetail](videotoolbox/kvtcompressionpropertykey_fielddetail.md)
- [kVTCompressionPropertyKey_ProgressiveScan](videotoolbox/kvtcompressionpropertykey_progressivescan.md)