iOS - video compressing with maintaining quality like WhatsApp but size reduced using Swift

Question

I am using UIImagePickerController and I want to reduce the file size of the video imported but quality still good:

I am using the following code:

func addAttachmentUtil(from : String)
    {
        let file = UIImagePickerController()
        file.delegate = self
        file.sourceType = UIImagePickerControllerSourceType.photoLibrary
        file.videoMaximumDuration = 600

        file.mediaTypes = ["public.image", "public.movie"]
        file.videoQuality = .type640x480

        file.allowsEditing = false

        self.present(file, animated: true)
        {
        }
    }

The code above compresses the video and the video loses its quality. How do I compress the video same like WhatsApp does and still maintain the quality?

I went through this answer at: iPhone:Programmatically compressing recorded video to share? but it is for Objective C and I am unable to figure out a Swift version for this. It will very helpful if someone could help me with a Swift version for this.