How to get the value of kCVPixelFormatType_DepthFloat16 (half-point float)?

user_7762885 0
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I am working with a project on iOS front depth camera with swift. The media type is kCVPixelFormatType_DepthFloat16, half-point float at 640*360 dimension with 30fps according to apple documentation. I was stuck in how to further retrieve and process the value pixel by pixel.

let buffer:CVPixelBuffer = depthData.depthDataMap //depthData is AVDepthData type
CVPixelBufferLockBaseAddress(buffer, CVPixelBufferLockFlags(rawValue: 0))
let width = CVPixelBufferGetWidth(buffer)
let height = CVPixelBufferGetHeight(buffer)
for y in 0 ..< height {
  for x in 0 ..< width {
    let pixel = ?? //what should I do here?
  }
}
half-precision-float swift ios
2 Answers

I have solved my problem already. This can be done in two ways.

  1. Use kCVPixelFormatType_DepthFloat32 instead of kCVPixelFormatType_DepthFloat16, it will have the same dimension and fps as the previous depthmap. Then you can convert it into Swift Float type like the following:
let width = CVPixelBufferGetWidth(buffer)
let height = CVPixelBufferGetHeight(buffer)

CVPixelBufferLockBaseAddress(buffer, CVPixelBufferLockFlags(rawValue: 0))
let floatBuffer = unsafeBitCast(CVPixelBufferGetBaseAddress(buffer), to: UnsafeMutablePointer<Float>.self)

for y in 0 ..< height {
    for x in 0 ..< width {
        let pixel = floatBuffer[y*width+x]
    }
}
CVPixelBufferUnlockBaseAddress(self, CVPixelBufferLockFlags(rawValue: 0))
  1. The second way is to convert to UInt16 first, then add two zero bytes before it
// to access the point height = y, width = x, thanks to this project https://github.com/edvardHua/Articles/tree/master/%5BAR:MR%20%E5%9F%BA%E7%A1%80%5D%20%E5%88%A9%E7%94%A8%20iPhone%20X%20%E7%9A%84%E6%B7%B1%E5%BA%A6%E7%9B%B8%E6%9C%BA(TruthDepth%20Camera)%E8%8E%B7%E5%BE%97%E5%83%8F%E7%B4%A0%E7%82%B9%E7%9A%84%E4%B8%89%E7%BB%B4%E5%9D%90%E6%A0%87/Obtain3DCoordinate
let rowData = CVPixelBufferGetBaseAddress(buffer)! + Int(y) *  CVPixelBufferGetBytesPerRow(buffer)
var f16Pixel = rowData.assumingMemoryBound(to: UInt16.self)[x]
var f32Pixel = Float(0.0)
var src = vImage_Buffer(data: &f16Pixel, height: 1, width: 1, rowBytes: 2)
var dst = vImage_Buffer(data: &f32Pixel, height: 1, width: 1, rowBytes: 4)
vImageConvert_Planar16FtoPlanarF(&src, &dst, 0)
let depth = f32Pixel //depth in cm
user_77628850

Can't you just do the following?

AVDepthData.converting(depthDataType : kCVPixelFormatType_DepthFloat16)
user_182810620
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