ios - 以高帧速率和低视频大小录制视频

Question

我正在尝试以120xps录制视频，格式为640x480。

我可以设置fps：

// currentCamera is an AVCaptureDevice, session is an AVCaptureSession
let input = try AVCaptureDeviceInput(device: currentCamera)
session.addInput(input)
let targetFrameRate = CMTimeMake(1, 120)
if let slowMoFormat = currentCamera.formats
  .flatMap({ return ($0 as? AVCaptureDeviceFormat) })
  .filter({ format in
    for x in format.videoSupportedFrameRateRanges {
      if let range = x as? AVFrameRateRange {
        if range.minFrameDuration <= targetFrameRate {
          return true
        }
      }
    }
    return false
  }).first {
  try currentCamera.lockForConfiguration()
  currentCamera.activeFormat = slowMoFormat
  currentCamera.activeVideoMinFrameDuration = targetFrameRate
  currentCamera.activeVideoMaxFrameDuration = targetFrameRate
  currentCamera.unlockForConfiguration()
}

或带

的视频尺寸

// session is an AVCaptureSession
session.sessionPreset = AVCaptureSessionPreset640x480

但我不能同时做到这两点，因为更改activeFormat或会话预设会覆盖其他更改。有什么明显的东西我不见了吗？