What’s new in camera capture

0:01 - Optimize QR code scanning

// Optimize the user experience for scanning QR codes down to sizes of 20mm x 20mm.

let deviceFieldOfView = self.videoDeviceInput.device.activeFormat.videoFieldOfView

let minSubjectDistance = minSubjectDistanceForCode(
  fieldOfView: deviceFieldOfView,
  minimumCodeSize: 20,
  previewFillPercentage: Float(rectOfInterestWidth))

0:02 - minSubjectDistance

private func minSubjectDistance(
  fieldOfView: Float,
  minimumCodeSize: Float,
  previewFillPercentage: Float) -> Float {
    let radians = degreesToRadians(fieldOfView / 2)
    let filledCodeSize = minimumCodeSize / previewFillPercentage
    return filledCodeSize / tan(radians)
}

0:03 - Lock device for configuration

let deviceMinimumFocusDistance = Float(self.videoDeviceInput.device.minimumFocusDistance)
if minimumSubjectDistanceForCode < deviceMinimumFocusDistance {
  let zoomFactor = deviceMinimumFocusDistance / minimumSubjectDistanceForCode
  do {
    try videoDeviceInput.device.lockForConfiguration()
    videoDeviceInput.device.videoZoomFactor = CGFloat(zoomFactor)
    videoDeviceInput.device.unlockForConfiguration()
  } catch {
    print("Could not lock for configuration: \(error)")
  }
}

0:04 - firstTenBitFormatOfDevice

func firstTenBitFormatOfDevice(device: AVCaptureDevice) -> AVCaptureDevice.Format? {
  for format in device.formats {
    let pixelFormat = CMFormatDescriptionGetMediaSubType(format.formatDescription)

    if pixelFormat == kCVPixelFormatType_420YpCbCr10BiPlanarVideoRange /* 'x420' */ {
      return format
    }
  }
  return nil
}

0:05 - captureOutput

func captureOutput(
  _ output: AVCaptureOutput,
  didDrop sampleBuffer: CMSampleBuffer,
  from connection: AVCaptureConnection) {
    guard let attachment = sampleBuffer.attachments[.droppedFrameReason],
          let reason = attachment.value as? String else { return }
    switch reason as CFString {
    case kCMSampleBufferDroppedFrameReason_FrameWasLate:
      // Handle the late frame case.
      break
    case kCMSampleBufferDroppedFrameReason_OutOfBuffer:
      // Handle the out of buffers case.
      break
    case kCMSampleBufferDroppedFrameReason_Discontinuity:
      // Handle the discontinuity case.
      break
    default:
      fatalError("A frame dropped for an undefined reason.")
    }
}