iPhone 7 Plus - AVFoundation 双摄像头

Question

我目前正在积极研究这一点，但现在 iPhone 7 Plus 具有双摄像头系统，AVFoundation 是否允许您同时处理来自每个特定摄像头的视频帧？

我正在考虑/希望在给定特定位置的情况下，我能够同时处理来自两个 AVCaptureDevice 实例的输出。

Answer 1

您一次只能将一台摄像机添加到 AVCaptureSession。例如，您可以在前后摄像头之间切换，但不能同时使用两者。 7 Plus 的两个后置摄像头也是如此，您必须选择其中一个。但是，有一个小的区别，因为您也可以调用“双摄像头”，在缩放时合并来自两个摄像头的图像。但这仅适用于静态照片，您只会获得一个图像/捕获缓冲区。对于视频，您必须选择任一相机。

要选择相机，您可以使用新的 AVCaptureDeviceDiscoverySession。要使用双摄像头：

@property (nonatomic) AVCaptureDevice *backCamera;
@property (nonatomic) AVCaptureDeviceInput *backCameraInput;


if([AVCaptureDeviceDiscoverySession class]){
    NSArray *allTypes = @[AVCaptureDeviceTypeBuiltInDuoCamera, AVCaptureDeviceTypeBuiltInWideAngleCamera, AVCaptureDeviceTypeBuiltInTelephotoCamera ];
    AVCaptureDeviceDiscoverySession *discoverySession = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:allTypes mediaType:AVMediaTypeVideo position:AVCaptureDevicePositionBack];

    for(AVCaptureDevice *device in discoverySession.devices) {
        if(device.deviceType== AVCaptureDeviceTypeBuiltInDuoCamera){
            self.backCamera = device;
            self.backCameraInput = [AVCaptureDeviceInput deviceInputWithDevice:self.backCamera error:&error];
        }
    }
}

if(!self.backCamera){
    self.backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    self.backCameraInput = [AVCaptureDeviceInput deviceInputWithDevice:self.backCamera error:&error];
}

单独使用广角和长焦相机

@property (nonatomic) AVCaptureDevice *backCamera;
@property (nonatomic) AVCaptureDeviceInput *backCameraInput;
@property (nonatomic) AVCaptureDevice *teleCamera;
@property (nonatomic) AVCaptureDeviceInput *teleCameraInput;


if([AVCaptureDeviceDiscoverySession class]){
    NSArray *allTypes = @[AVCaptureDeviceTypeBuiltInDuoCamera, AVCaptureDeviceTypeBuiltInWideAngleCamera, AVCaptureDeviceTypeBuiltInTelephotoCamera ];
    AVCaptureDeviceDiscoverySession *discoverySession = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:allTypes mediaType:AVMediaTypeVideo position:AVCaptureDevicePositionBack];

    for(AVCaptureDevice *device in discoverySession.devices) {
        if(device.deviceType==AVCaptureDeviceTypeBuiltInWideAngleCamera){
            self.backCamera = device;
            self.backCameraInput = [AVCaptureDeviceInput deviceInputWithDevice:self.backCamera error:&error];
        }

        if(device.deviceType==AVCaptureDeviceTypeBuiltInTelephotoCamera){
            self.teleCamera = device;
            self.teleCameraInput = [AVCaptureDeviceInput deviceInputWithDevice:self.teleCamera error:&error];
        }
    }
}

if(!self.backCamera){
    self.backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    self.backCameraInput = [AVCaptureDeviceInput deviceInputWithDevice:self.backCamera error:&error];
}

如果您不这样做，或者保留旧代码，即使您缩放，您也只会使用广角相机。

编辑：在 iOS 11 中有一个名为 dualCameraDualPhotoDeliveryEnabled 的新 AVCapturePhotoSettings。它允许您同时拍摄两张静止图像，但是，没有流媒体/视频。

Answer 2

在更新的 AVFoundation 文档 (AVCaptureDeviceType) 中有新的设备类型：builtInWideAngleCamera 和 builtInTelephotoCamera。因此，应该可以创建多个捕获会话并同时从它们两个获取反馈。