computer vision - How can I get Camera Calibration Data on iOS? aka AVCameraCalibrationData

Question

As I understand it, AVCameraCalibrationData is only available over AVCaptureDepthDataOutput. Is that correct?

AVCaptureDepthDataOutput on the other hand is only accessible with iPhone X front cam or iPhone Plus back cam, or am I mistaken?

What I am trying to do is to get the FOV of an AVCaptureVideoDataOutput SampleBuffer. Especially, it should match the selected preset (full HD, Photo etc.).

Answer 1

You can get AVCameraCalibrationData only from depth data output or photo output.

However, if all you need is FOV, you need only part of the info that class offers — the camera intrinsics matrix — and you can get that by itself from AVCaptureVideoDataOutput.

1. Set cameraIntrinsicMatrixDeliveryEnabled on the AVCaptureConnection connecting your camera device to the capture session. (Note you should check cameraIntrinsicMatrixDeliverySupported first; not all capture formats support intrinsics.)

2. When the video output vends sample buffers, check each sample buffer's attachments for the kCMSampleBufferAttachmentKey_CameraIntrinsicMatrix key. As noted in CMSampleBuffer.h (someone should file a radar about getting this info into the online documentation), the value for that attachment is a CFData encoding a matrix_float3x3, and the (0,0) and (1,1) elements of that matrix are the horizontal and vertical focal length in pixels.