使用 AVCaptureSession 切换前置/后置摄像头

Question

我正在关注 SO 上的唯一答案 -

Switch cameras with avcapturesession

但是 cameraWithPosition 似乎不起作用。已弃用？

//Get new input
    AVCaptureDevice *newCamera = nil;
    if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack)
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
    }
    else
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
    }

Answer 1

你需要做的是重新配置你的AVCaptureSession

这是我正在使用的：

// note that `AVCaptureSession * session`
//
if(session)
{
    [session beginConfiguration];

    AVCaptureInput *currentCameraInput = [session.inputs objectAtIndex:0];

    [session removeInput:currentCameraInput];

    AVCaptureDevice *newCamera = nil;

    if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack)
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
    }
    else
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
    }

    NSError *err = nil;

    AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];

    if(!newVideoInput || err)
    {
        NSLog(@"Error creating capture device input: %@", err.localizedDescription);
    }
    else
    {
        [session addInput:newVideoInput];
    }

    [session commitConfiguration];
}

// make sure you have this method in your class
//
- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in devices)
    {
        if ([device position] == position)
            return device;
    }
    return nil;
}

Answer 2

在 Swift 3.0 中

/// Swap camera and reconfigures camera session with new input
fileprivate func swapCamera() {

    // Get current input
    guard let input = cameraSession.inputs[0] as? AVCaptureDeviceInput else { return }

    // Begin new session configuration and defer commit
    cameraSession.beginConfiguration()
    defer { cameraSession.commitConfiguration() }

    // Create new capture device
    var newDevice: AVCaptureDevice?
    if input.device.position == .back {
        newDevice = captureDevice(with: .front)
    } else {
        newDevice = captureDevice(with: .back)
    }

    // Create new capture input
    var deviceInput: AVCaptureDeviceInput!
    do {
        deviceInput = try AVCaptureDeviceInput(device: newDevice)
    } catch let error {
        print(error.localizedDescription)
        return
    }

    // Swap capture device inputs
    cameraSession.removeInput(input)
    cameraSession.addInput(deviceInput)
}

/// Create new capture device with requested position
fileprivate func captureDevice(with position: AVCaptureDevicePosition) -> AVCaptureDevice? {

    let devices = AVCaptureDeviceDiscoverySession(deviceTypes: [ .builtInWideAngleCamera, .builtInMicrophone, .builtInDualCamera, .builtInTelephotoCamera ], mediaType: AVMediaTypeVideo, position: .unspecified).devices

    if let devices = devices {
        for device in devices {
            if device.position == position {
                return device
            }
        }
    }

    return nil
}

Answer 3

Swift 4.2 的代码更新

/// Swap camera and reconfigures camera session with new input
fileprivate func swapCamera() {

    // Get current input
    guard let input = captureSession.inputs[0] as? AVCaptureDeviceInput else { return }

    // Begin new session configuration and defer commit
    captureSession.beginConfiguration()
    defer { captureSession.commitConfiguration() }

    // Create new capture device
    var newDevice: AVCaptureDevice?
    if input.device.position == .back {
        newDevice = captureDevice(with: .front)
    } else {
        newDevice = captureDevice(with: .back)
    }

    // Create new capture input
    var deviceInput: AVCaptureDeviceInput!
    do {
        deviceInput = try AVCaptureDeviceInput(device: newDevice!)
    } catch let error {
        print(error.localizedDescription)
        return
    }

    // Swap capture device inputs
    captureSession.removeInput(input)
    captureSession.addInput(deviceInput)
}

/// Create new capture device with requested position
fileprivate func captureDevice(with position: AVCaptureDevice.Position) -> AVCaptureDevice? {

    let devices = AVCaptureDevice.DiscoverySession(deviceTypes: [ .builtInWideAngleCamera, .builtInMicrophone, .builtInDualCamera, .builtInTelephotoCamera ], mediaType: AVMediaType.video, position: .unspecified).devices

    //if let devices = devices {
        for device in devices {
            if device.position == position {
                return device
            }
        }
    //}

    return nil
}

Answer 4

Swift 5 的代码更新

extension CameraManager {
    func switchCamera() {
        captureSession.beginConfiguration()
        defer {captureSession.commitConfiguration()}

        let nextPosition = ((currentCameraInput as? AVCaptureDeviceInput)?.device.position == .front) ? AVCaptureDevice.Position.back : .front

        if let currentCameraInput = currentCameraInput {
            captureSession.removeInput(currentCameraInput)
        }

        if let newCamera = cameraDevice(position: nextPosition),
            let newVideoInput: AVCaptureDeviceInput = try? AVCaptureDeviceInput(device: newCamera),
            captureSession.canAddInput(newVideoInput) {

            captureSession.addInput(newVideoInput)
            currentCameraInput = newVideoInput

            videoDataOutput.connection(with: .video)?.videoOrientation = .portrait
            videoDataOutput.connection(with: .video)?.automaticallyAdjustsVideoMirroring = false
            videoDataOutput.connection(with: .video)?.isVideoMirrored = nextPosition == .front
        }
    }

    private func cameraDevice(position: AVCaptureDevice.Position) -> AVCaptureDevice? {
        let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)
        for device in discoverySession.devices where device.position == position {
            return device
        }

        return nil
    }
}

使用 AVCaptureSession 的相机的完整代码是this gist.

Answer 5

下面是一个在视频会话中使用开关的示例：

.h

UIViewController<AVCaptureFileOutputRecordingDelegate>

@property(nonatomic,strong)  AVCaptureSession *CaptureSession;
@property(nonatomic,strong) AVCaptureMovieFileOutput *MovieFileOutput;
@property(nonatomic,strong) AVCaptureDeviceInput *VideoInputDevice;

- (void) CameraSetOutputProperties;
- (AVCaptureDevice *) CameraWithPosition:(AVCaptureDevicePosition) Position;

然后：

.m

- (void)viewDidLoad {

   [super viewDidLoad];

   CaptureSession = [[AVCaptureSession alloc] init];

   //etc


}

- (IBAction)CameraToggle:(id)sender
{
    if ([[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count] > 1)        //Only do if device has multiple cameras
    {
        NSError *error;
        //AVCaptureDeviceInput *videoInput = [self videoInput];
        AVCaptureDeviceInput *NewVideoInput;
        AVCaptureDevicePosition position = [[VideoInputDevice device] position];
        if (position == AVCaptureDevicePositionBack)
        {
            NewVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self CameraWithPosition:AVCaptureDevicePositionFront] error:&error];
        }
        else if (position == AVCaptureDevicePositionFront)
        {
            NewVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self CameraWithPosition:AVCaptureDevicePositionBack] error:&error];
        }

        if (NewVideoInput != nil)
        {
            [CaptureSession beginConfiguration];
            [CaptureSession removeInput:VideoInputDevice];
            if ([CaptureSession canAddInput:NewVideoInput])
            {
                [CaptureSession addInput:NewVideoInput];
                VideoInputDevice = NewVideoInput;
            }
            else
            {
                [CaptureSession addInput:VideoInputDevice];
            }

            //Set the connection properties again
            [self CameraSetOutputProperties];


            [CaptureSession commitConfiguration];
        }
    }
}