我想知道是否可以通过单个相机设备输入将多个 AVCaptureVideoDataOutput
添加到 AVCaptureSession
?
我的实验表明,添加第二个 VideoDataOutput
将导致 canAddOutput
返回 NO
。但是我在 Apple 的文档中找不到任何地方说不允许多数据输出。
最佳答案
我们不能对多个 AVCaptureVideoDataOutput
对象使用单个 AVCaptureSession
。
您可以做的是使用多个 AVCaptureSession
对象制作多个 AVCaptureVideoDataOutput
。
您可以创建两个不同的 AVCaptureVideoDataOutput
和 AVCaptureSession
设置,然后您可以在应用程序中一个接一个地使用它们,您将能够实现目标。
在我的例子中,我必须同时使用相机拍摄正面和背面图像。
我确实为 AVCaptureVideoDataOutput
和 AVCaptureSession
创建了两个不同的对象,如下所示。
/* Front camera settings */
@property bool isFrontRecording;
@property (strong, nonatomic) AVCaptureDeviceInput *videoInputBack;
@property (strong, nonatomic) AVCaptureStillImageOutput *imageOutputBack;
@property (strong, nonatomic) AVCaptureSession *sessionBack;
/* Back camera settings */
@property bool isBackRecording;
@property (strong, nonatomic) AVCaptureDeviceInput *videoInputFront;
@property (strong, nonatomic) AVCaptureStillImageOutput *imageOutputFront;
@property (strong, nonatomic) AVCaptureSession *sessionFront;
现在在 View 中最初加载我设置了后置摄像头并设置了 session 开始记录或不开始记录的标志,如下所示。
- (void)viewDidLoad {
[super viewDidLoad];
[self setupBackAVCapture];
self.isFrontRecording = NO;
self.isBackRecording = NO;
}
- (void)setupBackAVCapture
{
NSError *error = nil;
self.sessionBack = [[AVCaptureSession alloc] init];
self.sessionBack.sessionPreset = AVCaptureSessionPresetPhoto;
AVCaptureDevice *camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
self.videoInputBack = [[AVCaptureDeviceInput alloc] initWithDevice:camera error:&error];
[self.sessionBack addInput:self.videoInputBack];
self.imageOutputBack = [[AVCaptureStillImageOutput alloc] init];
[self.sessionBack addOutput:self.imageOutputBack];
}
现在,每当用户开始拍摄照片时,我们都会使用以下代码拍摄正面照片。
- (IBAction)buttonCapture:(id)sender {
[self takeBackPhoto];
}
- (void)takeBackPhoto
{
[self.sessionBack startRunning];
if (!self.isFrontRecording) {
self.isFrontRecording = YES;
AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
AVCaptureConnection *videoConnection = [self.imageOutputBack connectionWithMediaType:AVMediaTypeVideo];
if (videoConnection == nil) {
return;
}
[self.imageOutputBack
captureStillImageAsynchronouslyFromConnection:videoConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
if (imageDataSampleBuffer == NULL) {
return;
}
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
[self.imageView setImage:image];
[self.sessionBack stopRunning];
// Set up front camera setting and capture photo.
[self setupFrontAVCapture];
[self takeFrontPhoto];
}];
self.isFrontRecording = NO;
}
}
一旦捕获到背面图像,我们将设置 session 以使用 setupFrontAVCapture 方法捕获正面图像,然后我们将使用 takeFrontPhoto 方法捕获正面图像,如下所示.
- (void)setupFrontAVCapture
{
NSError *error = nil;
self.sessionFront = [[AVCaptureSession alloc] init];
self.sessionFront.sessionPreset = AVCaptureSessionPresetPhoto;
AVCaptureDevice *camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
camera = [self cameraWithPosition:AVCaptureDevicePositionFront];
self.videoInputFront = [[AVCaptureDeviceInput alloc] initWithDevice:camera error:&error];
[self.sessionFront addInput:self.videoInputFront];
self.imageOutputFront = [[AVCaptureStillImageOutput alloc] init];
[self.sessionFront addOutput:self.imageOutputFront];
}
- (void)takeFrontPhoto
{
[self.sessionFront startRunning];
if (!self.isBackRecording) {
self.isBackRecording = YES;
AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
AVCaptureConnection *videoConnection = [self.imageOutputFront connectionWithMediaType:AVMediaTypeVideo];
if (videoConnection == nil) {
return;
}
[self.imageOutputFront
captureStillImageAsynchronouslyFromConnection:videoConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
if (imageDataSampleBuffer == NULL) {
return;
}
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
[self.imageViewBack setImage:image];
[self.sessionFront stopRunning];
}];
self.isBackRecording = NO;
}
}
这样你就可以使用两组不同的 AVCaptureSession
和 AVCaptureStillImageOutput
对象,你可以实现你的目标。
如果您有任何困惑,请告诉我。
关于ios - 同一个 AVCaptureSession 中的多个 AVCaptureVideoDataOutput,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44577331/