【Swift4】動画撮影時に音声にイコライザーをかけて保存する方法を教えて下さい

前提・実現したいこと

動画撮影時の入力音声にイコライザー処理を行った上で、カメラロールに保存したいです。

発生している問題・エラーメッセージ

通常の動画撮影と保存は問題なくできています。
イコライザー処理にはAVAudioEngineを使用しようと思っています。

動画撮影
↓
入力された音声にイコライザーをかける
↓
イコライザー処理がかかった状態で動画としてカメラロールに保存

上記を実装するためにはどのようにすればよいのでしょうか？
（そもそも上記の実装は可能なのでしょうか？）

何卒ご教示のほどよろしくお願いいたします。

該当のソースコード

ViewController
1import UIKit
2import AVFoundation
3import Photos
4
5class ViewController: UIViewController, AVCaptureFileOutputRecordingDelegate {
6    
7    var session: AVCaptureSession!
8    var videoDevice: AVCaptureDevice!
9    var audioDevice: AVCaptureDevice!
10    var fileOutput: AVCaptureFileOutput!
11    var isRecording = false
12    
13    @IBOutlet weak var recordButton: UIButton!
14    
15    override func viewDidLoad() {
16        super.viewDidLoad()
17        
18        session = AVCaptureSession()
19        videoDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)
20        let videoInput = try! AVCaptureDeviceInput.init(device: videoDevice)
21        session.addInput(videoInput)
22        
23        audioDevice = AVCaptureDevice.default(for: .audio)
24        let audioInput = try! AVCaptureDeviceInput.init(device: audioDevice)
25        session.addInput(audioInput)
26        
27        fileOutput = AVCaptureMovieFileOutput()
28        session.addOutput(fileOutput)
29        
30        session.commitConfiguration()
31        session.startRunning()
32        
33        setUpPreview()
34        
35    }
36    
37    func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {
38        PHPhotoLibrary.shared().performChanges({
39            PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: outputFileURL)
40        }) { (isCompleted, error) in
41            if isCompleted {
42                print("Saved")
43            }
44        }
45    }
46    
47    func setUpPreview() {
48        let previewLayer: AVCaptureVideoPreviewLayer!
49        previewLayer = AVCaptureVideoPreviewLayer(session: session)
50        previewLayer.frame = self.view.bounds
51        previewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill
52        self.view.layer.insertSublayer(previewLayer, at: 0)
53        
54    }
55    
56    @IBAction func tapRecordButton(_ sender: Any) {
57        onClickRecordButton()
58    }
59    
60    func startRecording() {
61        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
62        let documentDirectry = paths[0] as String
63        let formatter = DateFormatter()
64        formatter.dateFormat = "yyyyMMddHHmmSS"
65        let filePath: String? = "(documentDirectry)/video-(formatter.string(from: Date())).mp4"
66        let fileURL = NSURL(fileURLWithPath: filePath!)
67        print("Start recording")
68        fileOutput?.startRecording(to: fileURL as URL, recordingDelegate: self)
69        recordButton.setImage(UIImage.init(named: "stop"), for: UIControl.State.normal)
70    }
71    
72    func stopRecording() {
73        print("Stop recording")
74        fileOutput?.stopRecording()
75        recordButton.setImage((UIImage.init(named: "start")), for: UIControl.State.normal)
76    }
77    
78    func onClickRecordButton() {
79        if !isRecording {
80            startRecording()
81            isRecording = true
82        } else {
83            stopRecording()
84            isRecording = false
85        }
86    }
87    
88    // ここから下がイコライザーの部分
89    var audioEngine = AVAudioEngine()
90    func setup() {
91        let audioSession = AVAudioSession.sharedInstance()
92        do {
93            try audioSession.setActive(true)
94        } catch let error as NSError  {
95            print("Error : (error)")
96        }
97
98        let input = audioEngine.inputNode
99        let mixer = audioEngine.mainMixerNode
100        
101        // Reverb
102        let reverb = AVAudioUnitReverb()
103        reverb.loadFactoryPreset(.largeRoom)
104        audioEngine.attach(reverb)
105        
106        // Delay
107        let delay = AVAudioUnitDelay()
108        delay.delayTime = 1
109        audioEngine.attach(delay)
110        
111        // EQ
112        let eq = AVAudioUnitEQ()
113        audioEngine.attach(eq)
114
115        audioEngine.connect(input, to: reverb, format: input.inputFormat(forBus: 0))
116        audioEngine.connect(reverb, to: delay, format: input.inputFormat(forBus: 0))
117        audioEngine.connect(delay, to: eq, format: input.inputFormat(forBus: 0))
118        audioEngine.connect(eq, to: mixer, format: input.inputFormat(forBus: 0))
119        
120        // Distortion
121        let distortion = AVAudioUnitDistortion()
122        distortion.loadFactoryPreset(.speechAlienChatter)
123        audioEngine.attach(distortion)
124        
125        audioEngine.connect(input, to: distortion, format: input.inputFormat(forBus: 0))
126        audioEngine.connect(distortion, to: mixer, format: input.inputFormat(forBus: 0))
127    }
128}
129
130