AVCaptureDeviceInput is a crucial component in the AVFoundation framework, which is used for capturing media such as video and audio in macOS and iOS applications. It allows developers to capture input from a device like a camera or microphone and process it in real-time. This is particularly important for applications that require live video streaming, video conferencing, or any real-time media processing.

In this article, we will explore how to set up and use AVCaptureDeviceInput in a macOS application. We will cover the basics of initializing the capture session, selecting the input device, and handling errors. This guide assumes you have a basic understanding of Swift and macOS development.

Examples:

1. Setting Up the Capture Session

   First, you need to import the AVFoundation framework and create an instance of AVCaptureSession.

   import AVFoundation
   
   class ViewController: NSViewController {
      var captureSession: AVCaptureSession?
   
      override func viewDidLoad() {
          super.viewDidLoad()
          setupCaptureSession()
      }
   
      func setupCaptureSession() {
          captureSession = AVCaptureSession()
          captureSession?.sessionPreset = .high
      }
   }

2. Selecting the Input Device

   Next, you need to select the input device, such as the built-in camera. You can use AVCaptureDevice.default to get the default video device.

   func setupCaptureSession() {
      captureSession = AVCaptureSession()
      captureSession?.sessionPreset = .high
   
      guard let videoDevice = AVCaptureDevice.default(for: .video) else {
          print("No video device found")
          return
      }
   
      do {
          let videoInput = try AVCaptureDeviceInput(device: videoDevice)
          if captureSession?.canAddInput(videoInput) == true {
              captureSession?.addInput(videoInput)
          }
      } catch {
          print("Error creating video input: \(error)")
      }
   }

3. Starting the Capture Session

   Finally, you need to start the capture session to begin capturing video.

   func startCaptureSession() {
      captureSession?.startRunning()
   }
   
   override func viewDidAppear() {
      super.viewDidAppear()
      startCaptureSession()
   }

4. Handling Errors

   It's important to handle any potential errors that might occur during the setup or running of the capture session.

   func setupCaptureSession() {
      captureSession = AVCaptureSession()
      captureSession?.sessionPreset = .high
   
      guard let videoDevice = AVCaptureDevice.default(for: .video) else {
          print("No video device found")
          return
      }
   
      do {
          let videoInput = try AVCaptureDeviceInput(device: videoDevice)
          if captureSession?.canAddInput(videoInput) == true {
              captureSession?.addInput(videoInput)
          } else {
              print("Cannot add video input")
          }
      } catch {
          print("Error creating video input: \(error)")
      }
   }

By following these steps, you can set up and use AVCaptureDeviceInput in your macOS applications to capture and process media from input devices like cameras and microphones.