iOS 9以每秒60帧的速度录制视频

正在尝试使用AVFoundation和Swift以每秒60帧的速度录制视频，但下面的代码不起作用。即使设置了60fps，视频仍以30fps的速度录制

captureSession = AVCaptureSession()

var finalFormat = AVCaptureDeviceFormat()
var maxFps: Double = 0
for vFormat in camera!.formats
{
    var ranges      = vFormat.videoSupportedFrameRateRanges as!  [AVFrameRateRange]
    let frameRates  = ranges[0]
    if frameRates.maxFrameRate >= maxFps && frameRates.maxFrameRate <= 60
    {
        maxFps = frameRates.maxFrameRate
        finalFormat = vFormat as! AVCaptureDeviceFormat
    }
}

print(String(maxFps) + " fps"); //prints 60 fps
try camera!.lockForConfiguration()
camera!.activeFormat = finalFormat
camera!.activeVideoMinFrameDuration = CMTimeMake(1, 60)
camera!.activeVideoMaxFrameDuration = CMTimeMake(1, 60)
camera!.unlockForConfiguration()

let video = try AVCaptureDeviceInput(device: camera) as AVCaptureDeviceInput
captureSession!.addInput(video)

let audio = try AVCaptureDeviceInput(device: AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeAudio)) as AVCaptureDeviceInput
captureSession!.addInput(audio)

fileOutput = AVCaptureMovieFileOutput()

captureSession?.addOutput(fileOutput)

captureSession!.startRunning()

captureSession=AVCaptureSession（）
var finalFormat=AVCaptureDeviceFormat（）
var maxFps:Double=0
对于摄像机中的vFormat！。格式
{
var ranges=vFormat.videoSupportedFrameRateRanges as！[AVFrameRateRange]
设帧率=范围[0]
如果frameRates.maxFrameRate>=maxFps&&frameRates.maxFrameRate在创建AVCaptureDeviceInput后设置相机属性有效

let video = try AVCaptureDeviceInput(device: camera) as AVCaptureDeviceInput
captureSession!.addInput(video)

print(String(maxFps) + " fps"); //prints 60 fps
try camera!.lockForConfiguration()
camera!.activeFormat = finalFormat
camera!.activeVideoMinFrameDuration = CMTimeMake(1, 60)
camera!.activeVideoMaxFrameDuration = CMTimeMake(1, 60)
camera!.unlockForConfiguration()

你知道只有iphone 6或更高版本才有这个功能，对吗？是的。我正在用iphone 6S进行测试。该设备使用本机摄像头，以60fps的速度进行记录？是的。用ipad和iphone进行了测试。