将AVCapture设置为60 FPS，iOS，Swift 4

Question

我试图将设置为1080p的后置相机设置为60 FPS，但代码和教程会在设置fps之前循环显示相机格式。

有没有办法设置fps而不会在所有不同的格式中循环？它需要很长时间骑自行车，有时会崩溃。

下面是我的代码

func setFPS() {
    captureSession = AVCaptureSession()
//      var finalFormat = AVCaptureDevice.Format
    var maxFps: Double = 0
    for vFormat in backCamera!.formats
    {
        print("Tony active formats are: \(vFormat)")
        var ranges = vFormat.videoSupportedFrameRateRanges as [AVFrameRateRange]
        let frameRates = ranges[0]
        if frameRates.maxFrameRate > 30
        {
            maxFps = frameRates.maxFrameRate
            do {
            try backCamera!.lockForConfiguration()
            backCamera!.activeFormat = vFormat
            backCamera!.activeVideoMinFrameDuration = CMTimeMake(1, 60)
            backCamera!.activeVideoMaxFrameDuration = CMTimeMake(1, 60)
            backCamera!.unlockForConfiguration()
            print("Tony the Max FPS is \(maxFps) fps"); //prints 60 fps
//              finalFormat = vFormat
            }catch {
                print("Error on frame rate")
            }
        }
    }

    print(String(maxFps) + " fps"); //prints 60 fps
    print("Tony the FPS is \(backCamera!.activeVideoMaxFrameDuration.timescale) fps") //prints 60 fps


}