---
title: "channelDescription(bufferType:)"
framework: accelerate
role: symbol
role_heading: Instance Method
path: "accelerate/vimagecvimageformat/channeldescription(buffertype:)"
---

# channelDescription(bufferType:)

Returns the range and clamp limits for a specified channel in a Core Video image format.

## Declaration

```swift
func channelDescription(bufferType: vImage.BufferType) -> vImageChannelDescription?
```

## Parameters

- `bufferType`: The source buffer type.

## Return Value

Return Value A vImageChannelDescription structure that describes the range and clamp limits for the specified channel.

## Discussion

Discussion Use this function to return the vImageChannelDescription description for a specified channel in a Core Video format. For example, the following code prints the description of each channel in a kCVPixelFormatType_420YpCbCr8Planar Core Video image format: let cvImageFormat = vImageCVImageFormat.make(     format: .format420YpCbCr8Planar,     matrix: kvImage_ARGBToYpCbCrMatrix_ITU_R_709_2.pointee,     chromaSiting: .center,     colorSpace: CGColorSpace(name: CGColorSpace.sRGB)!,     alphaIsOpaqueHint: true)!

// Prints: //    luminance   vImageChannelDescription(min: 0.0, zero: 16.0, full: 235.0, max: 255.0) //    Cb          vImageChannelDescription(min: 0.0, zero: 128.0, full: 240.0, max: 255.0) //    Cr          vImageChannelDescription(min: 0.0, zero: 128.0, full: 240.0, max: 255.0) for channel in cvImageFormat.channels {     let desc = cvImageFormat.channelDescription(bufferType: channel)!     print("\(channel) \t\t \(desc)") }

## See Also

### Related Documentation

- [vImageCVImageFormat_CopyChannelDescription(_:_:_:)](accelerate/vimagecvimageformat_copychanneldescription(_:_:_:).md)

### Inspecting a Core Video image format’s properties

- [channelCount](accelerate/vimagecvimageformat/channelcount.md)
- [channels](accelerate/vimagecvimageformat/channels.md)
- [formatCode](accelerate/vimagecvimageformat/formatcode.md)
- [chromaSiting](accelerate/vimagecvimageformat/chromasiting-swift.property.md)
- [colorSpace](accelerate/vimagecvimageformat/colorspace.md)
- [alphaIsOpaqueHint](accelerate/vimagecvimageformat/alphaisopaquehint.md)