I want to see a video preview on my iPhone's display with 240 fps.
My Code (simplyfied) is like this (following):
A session is made, the camera is activated and the actual video preview is shown on the display.
var session: AVCaptureSession?
var stillImageOutput: AVCaptureStillImageOutput?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
override func viewDidLoad() {
super.viewDidLoad()
super.viewWillAppear(true)
session = AVCaptureSession()
let backCamera = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
var error: NSError?
var input: AVCaptureDeviceInput!
do {
input = try AVCaptureDeviceInput(device: backCamera)
} catch let errorgesehen as NSError {
error = errorgesehen
input = nil
print(error!.localizedDescription)
}
configureCameraForHighestFrameRate(device: backCamera!)
if error == nil && session!.canAddInput(input) {
session!.addInput(input)
}
videoPreviewLayer = AVCaptureVideoPreviewLayer(session: session)
videoPreviewLayer!.videoGravity = AVLayerVideoGravityResizeAspect
videoPreviewLayer!.frame = CGRect(x: 0.0, y: 0.0, width: view.bounds.size.width, height: view.bounds.size.height)
videoPreviewLayer!.backgroundColor = UIColor(red: 0, green: 1, blue: 0, alpha: 1).cgColor
view.layer.addSublayer(videoPreviewLayer!)
session?.startRunning()
UIApplication.shared.isIdleTimerDisabled = true
}
Now I wanted that this video preview is shown in 240fps (60 or 120 would be ok too, but 240 is the best).
To solve this problem, I have used this: https://developer.apple.com/documentation/avfoundation/avcapturedevice (I have transformed it to Swift).
The function configureCameraForHighestFrameRate has the following code:
func configureCameraForHighestFrameRate(device: AVCaptureDevice) {
var bestFormat: AVCaptureDeviceFormat? = nil
var bestFrameRateRange: AVFrameRateRange? = nil
for formatf in device.formats {
var format = formatf as! AVCaptureDeviceFormat
print(format)
for rangef in format.videoSupportedFrameRateRanges {
var range = rangef as! AVFrameRateRange
print(range)
if (bestFrameRateRange == nil) {
bestFormat = format
bestFrameRateRange = range
} else if range.maxFrameRate > bestFrameRateRange!.maxFrameRate {
bestFormat = format
bestFrameRateRange = range
}
}
}
if (bestFormat == nil) {
print("Es gibt keine Formate, die Apokalypse ist ausgebrochen.")
return;
} else if (bestFrameRateRange == nil) {
print("Es gibt keine Bilder, die Apokalypse ist ausgebrochen.")
return;
}
let Richtig = bestFormat!
let fps = bestFrameRateRange!
do {
try device.lockForConfiguration()
}
catch let error as NSError {
print(error.description)
}
device.activeFormat = Richtig
device.activeVideoMinFrameDuration = fps.minFrameDuration
device.activeVideoMaxFrameDuration = fps.minFrameDuration
device.unlockForConfiguration()
}
This code looks for the AVCaptureDeviceFormat in which the fps number is maximal (=240). The actual format is set to this Format ans the fps number to the maximum (=240).
But I have the problem that the video output still contains only 30 frames per secons (if I turn the iPhone very quickly, I will recognize it).
Additionally, there are several formats in which the maximal fps are 240. This code only choses the first of them, but I ask me whether there is a differnce and which to choose to get the best output. Can anybody say a difference of the several formts or which of them is the format, the "Camera" App uses in the Slow Motion tool?
Thank you very much :)
