iOS：AVCaptureSession 录制的音频不会超过 11 秒

Question

我正在构建这个iPad应用程序来录制带有音频的视频。当视图出现时，它开始记录，然后您可以使用按钮停止录制，否则当计时器达到 0 时它将停止。

这是整个控制器类。

import UIKit
import AVKit
class RecorderController: UIViewController, AVCaptureFileOutputRecordingDelegate {
@IBOutlet weak var previewView: UIView!
@IBOutlet weak var countdownLabel: UILabel!
var videoUrl: URL?
var seconds = 11 // Works with 11 seconds, any thing longer audio disappears
var timer = Timer()
var captureSession: AVCaptureSession?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
var fileName: String = ""
var documentsURL: URL?
var filePath: URL?
let videoFileOutput = AVCaptureMovieFileOutput()
override func viewDidLoad() {
super.viewDidLoad()
previewView.layer.cornerRadius = 15
previewView.clipsToBounds = true
}
override func viewDidAppear(_ animated: Bool) {
startVideoRecording()
let recordingDelegate: AVCaptureFileOutputRecordingDelegate? = self
videoPreviewLayer!.frame.size = previewView.frame.size
videoFileOutput.startRecording(to: filePath!, recordingDelegate: recordingDelegate!)
runTimer()
}
func runTimer() {
countdownLabel.text = "(seconds)"
timer = Timer.scheduledTimer(timeInterval: 1, target: self,   selector: #selector(updateTimer), userInfo: nil, repeats: true)
}
@objc func updateTimer() {
seconds -= 1     //This will decrement(count down)the seconds.
countdownLabel.text = "(seconds)" //This will update the label.
if (seconds == 0) {
timer.invalidate()
stopRecording()
}
}
func startVideoRecording() {
let captureDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .front)
let captureAudio = AVCaptureDevice.default(for: .audio)
fileName = "mysavefile.mp4"
documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
filePath = documentsURL?.appendingPathComponent(fileName)  //.URLByAppendingPathComponent(fileName)
do {
let input = try AVCaptureDeviceInput(device: captureDevice!)
let audio = try AVCaptureDeviceInput(device: captureAudio!)
captureSession = AVCaptureSession()
captureSession?.sessionPreset = .high
captureSession?.addInput(input)
captureSession?.addInput(audio)
videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
videoPreviewLayer?.videoGravity = .resizeAspectFill
videoPreviewLayer?.frame.size = previewView.frame.size
previewView.layer.addSublayer(videoPreviewLayer!)
self.captureSession!.addOutput(videoFileOutput)
captureSession?.startRunning()
} catch {
print(error)
}
}
@IBAction func stopButton(_ sender: Any) {
stopRecording()
}
func stopRecording() {
videoFileOutput.stopRecording()
}
func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {
videoUrl = outputFileURL
captureSession?.stopRunning()
videoPreviewLayer?.removeFromSuperlayer()
self.performSegue(withIdentifier: "showViewer", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let transition = CATransition()
transition.duration = 0.5
transition.type = kCATransitionPush
transition.subtype = kCATransitionFromRight
transition.timingFunction = CAMediaTimingFunction(name:kCAMediaTimingFunctionEaseInEaseOut)
self.view.window!.layer.add(transition, forKey: kCATransition)
guard let vc = segue.destination as? ViewerController else { return }
vc.videoUrl = self.videoUrl
self.present(vc, animated: false, completion: nil)
}
}

如果我将计时器设置为 11 秒或更低，则录制视频时音频非常好。但真正奇怪的是，如果我将计时器增加到超过 11 秒的任何时间，并在计时器达到 0 时让录音停止，录音绝对没有声音。

任何想法可能导致这种情况？

Answer 1

我遇到了同样的问题，并在这篇文章中找到了解决方案：https://stackoverflow.com/a/31089253/1117968

您应该能够通过设置来解决问题：

videoFileOutput.movieFragmentInterval = kCMTimeInvalid

在开始录制之前。