ios - AVCaptureAudioDataOutputSampleBufferDelegate 未调用 captureOutput

Question

我有一个录制视频的应用，但我需要它向用户实时显示麦克风捕获的声音的音高水平。我已经能够使用 AVCaptureSession 成功地将音频和视频录制到 MP4 .但是，当我添加 AVCaptureAudioDataOutput到 session 并分配 AVCaptureAudioDataOutputSampleBufferDelegate我没有收到任何错误，但是 captureOutput一旦 session 开始，函数就永远不会被调用。

代码如下:

import UIKit
import AVFoundation
import CoreLocation


class ViewController: UIViewController, 
AVCaptureVideoDataOutputSampleBufferDelegate, 
AVCaptureFileOutputRecordingDelegate, CLLocationManagerDelegate , 
AVCaptureAudioDataOutputSampleBufferDelegate {

var videoFileOutput: AVCaptureMovieFileOutput!
let session = AVCaptureSession()
var outputURL: URL!
var timer:Timer!
var locationManager:CLLocationManager!
var currentMagnitudeValue:CGFloat!
var defaultMagnitudeValue:CGFloat!
var visualMagnitudeValue:CGFloat!
var soundLiveOutput: AVCaptureAudioDataOutput!


override func viewDidLoad() {
    super.viewDidLoad()
    self.setupAVCapture()
}


func setupAVCapture(){

    session.beginConfiguration()

    //Add the camera INPUT to the session
    let videoDevice = AVCaptureDevice.default(.builtInWideAngleCamera,
                                              for: .video, position: .front)
    guard
        let videoDeviceInput = try? AVCaptureDeviceInput(device: videoDevice!),
        session.canAddInput(videoDeviceInput)
        else { return }
    session.addInput(videoDeviceInput)

    //Add the microphone INPUT to the session
    let microphoneDevice = AVCaptureDevice.default(.builtInMicrophone, for: .audio, position: .unspecified)
    guard
        let audioDeviceInput = try? AVCaptureDeviceInput(device: microphoneDevice!),
        session.canAddInput(audioDeviceInput)
        else { return }
    session.addInput(audioDeviceInput)

    //Add the video file OUTPUT to the session
    videoFileOutput = AVCaptureMovieFileOutput()
    guard session.canAddOutput(videoFileOutput) else {return}
    if (session.canAddOutput(videoFileOutput)) {
        session.addOutput(videoFileOutput)
    }

    //Add the audio output so we can get PITCH of the sounds
    //AND assign the SampleBufferDelegate
    soundLiveOutput = AVCaptureAudioDataOutput()
    soundLiveOutput.setSampleBufferDelegate(self, queue: DispatchQueue(label: "test"))
    if (session.canAddOutput(soundLiveOutput)) {
        session.addOutput(soundLiveOutput)
        print ("Live AudioDataOutput added")
    } else
    {
        print("Could not add AudioDataOutput")
    }



    //Preview Layer
    let previewLayer = AVCaptureVideoPreviewLayer(session: session)
    let rootLayer :CALayer = self.cameraView.layer
    rootLayer.masksToBounds=true
    previewLayer.frame = rootLayer.bounds
    rootLayer.addSublayer(previewLayer)
    previewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill;

    //Finalize the session
    session.commitConfiguration()

   //Begin the session
    session.startRunning()


}

func captureOutput(_: AVCaptureOutput, didOutput: CMSampleBuffer, from: 
AVCaptureConnection) {
    print("Bingo")
}

}

预期输出:

Bingo
Bingo
Bingo
...

我已阅读:

StackOverflow: captureOutput not being called - 用户未正确声明 captureOutput 方法。

StackOverflow: AVCaptureVideoDataOutput captureOutput not being called - 用户根本没有声明 captureOutput 方法。

Apple - AVCaptureAudioDataOutputSampleBufferDelegate - Apple 关于委托(delegate)及其方法的文档 - 该方法与我声明的方法相匹配。

我在网上遇到的其他常见错误:

• 使用旧版本 Swift 的声明(我使用的是 v4.1)
• 显然是在 Swift 4.0 之后的一篇文章中，AVCaptureMetadataOutput替换 AVCaptureAudioDataOutput - 虽然我在 Apple 的文档中找不到这个，但我也试过这个，但类似的是，metadataOutput函数永远不会被调用。

我没有想法。我是否遗漏了一些明显的东西？

Answer 1

好吧，没有人回复我，但在玩弄它之后，我找到了为 Swift4 声明 captureOutput 方法的正确方法如下:

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
    //Do your stuff here
}

不幸的是，这个在线文档很差。我猜你只需要完全正确 - 如果你拼错或错误命名变量，也不会抛出任何错误，因为它是一个可选函数。