TN3145: HDR video metadata

How to attach ambientViewingEnvironment to new pixel buffer as attachment? I tried many things but it fails.

Update: It seems the attachment needs to be copied as NSData, example

 CVBufferSetAttachment(pixelBuffer, kCVImageBufferAmbientViewingEnvironmentKey, ambientViewingEnvironmentData! as NSData, .shouldPropagate)

@Jason It seems AVAssetWriter is crashing with error -12743 when appending NSData for kCVImageBufferAmbientViewingEnvironmentKey. Please describe how exactly to copy this attachment to new pixel buffer. Here is my code:

    var ambientViewingEnvironment:CMFormatDescription.Extensions.Value?
    var ambientViewingEnvironmentData:NSData?
     ambientViewingEnvironment = sampleBuffer.formatDescription?.extensions[.ambientViewingEnvironment]
     let plist = ambientViewingEnvironment?.propertyListRepresentation
       ambientViewingEnvironmentData = plist as? NSData

And then attaching this data,

   CVBufferSetAttachment(renderedPixelBuffer, kCVImageBufferAmbientViewingEnvironmentKey, ambientViewingEnvironmentData! as CFData, .shouldPropagate)