I have a setup in which I capture both photos from the actual devices of the virtual .builtinDualCamera. I set the videoZoomFactor of the virtual device to the first of virtualDeviceSwitchOverVideoZoomFactors. Taking a photo results in two AVCapturePhotos. One from the wide angle camera and one from the telephoto camera. Since the photo from the wide angle camera is zoomed in, a part of the photo black (this is to be expected).
On an iPhone X, the photo from the wide angle camera has a scale of 1 divided by that videoZoomFactor (1.8), which is what I would expect.
On an iPhone 14 Pro, however, the scale seems to be different from the expected 1.0 / 3.0! The scale is often smaller, but in these examples it is even bigger. The image is also not completely centered!
Why is this? And is there a way to calculate this scale and offset?
My setup (simplified):
import AVFoundation
class DualCamera {
enum DualCameraError: Error {
case initialisation
}
private let device: AVCaptureDevice
private let deviceInput: AVCaptureDeviceInput
private let session = AVCaptureSession()
private let photoOutput = AVCapturePhotoOutput()
private let queue = DispatchQueue(label: "camera queue")
private let cameraDelegate = DualCameraDelegate()
init() throws {
guard
let device = AVCaptureDevice.DiscoverySession(
deviceTypes: [.builtInDualCamera],
mediaType: .video,
position: .back)
.devices
.first,
let deviceInput = try? AVCaptureDeviceInput(device: device)
else {
throw DualCameraError.initialisation
}
self.device = device
self.deviceInput = deviceInput
session.sessionPreset = AVCaptureSession.Preset.photo
session.addInput(deviceInput)
session.addOutput(photoOutput)
photoOutput.isVirtualDeviceConstituentPhotoDeliveryEnabled = true
deviceConfiguration { device in
if let zoomFactor = device.virtualDeviceSwitchOverVideoZoomFactors.first {
device.videoZoomFactor = CGFloat(zoomFactor.floatValue)
}
}
}
func deviceConfiguration(_ configuration: @escaping (AVCaptureDevice)->()) {
queue.async { [self] in
session.beginConfiguration()
do {
try device.lockForConfiguration()
configuration(device)
device.unlockForConfiguration()
} catch(let error) {
print(error.localizedDescription)
}
session.commitConfiguration()
}
}
func shoot() {
queue.async { [self] in
let photoSettings = AVCapturePhotoSettings()
photoSettings.virtualDeviceConstituentPhotoDeliveryEnabledDevices = device.constituentDevices
photoOutput.capturePhoto(with: photoSettings, delegate: cameraDelegate)
}
}
}
class DualCameraDelegate: NSObject, AVCapturePhotoCaptureDelegate {
func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
// Do something with the photo
print(photo)
}
}
Note:
I expect AVCameraCalibrationData to be of help, but I cannot figure out how to use it with the limited documentation available.