苹果音乐与AVAudioEngine在斯威夫特

Question

如何使用AVAudioPlayerNode/AVAudioEngine访问Apple库中的歌曲以进行播放和处理？

我在苹果论坛上问过这个问题。

Answer 1

“苹果音乐”可指：

• 音乐流媒体服务
• 它的iOS客户端(称为“音乐”)
• 它的macOS客户端，作为本地媒体管理和播放应用程序(以前称为iTunes，macOS Catalina被称为“音乐”)。

由于DRM的限制，无法播放从苹果音乐目录下载到您的设备从苹果音乐macOS或iOS客户端的曲目。但是，您可以播放您拥有的并且有使用macOS音乐应用程序或Finder应用程序安装到设备上的音频文件，如下所示：

1. 将NSAppleMusicUsageDescription键添加到Info.plist文件及其相应的值
2. 设置AVAudioSession和AVAudioEngine
3. 查找您想要播放的媒体项的URL (您可以使用MPMediaPickerController，如下面的示例所示，也可以创建自己的MPMediaQuery)
4. 从该URL创建一个AVAudioFile
5. 创建一个AVAudioPlayerNode集来播放该AVAudioFile
6. 将player节点连接到引擎的输出节点

import UIKit
import AVFoundation
import MediaPlayer

class ViewController: UIViewController {

    let engine = AVAudioEngine()

    override func viewDidLoad() {
        super.viewDidLoad()

        let mediaPicker = MPMediaPickerController(mediaTypes: .music)
        mediaPicker.allowsPickingMultipleItems = false
        mediaPicker.showsItemsWithProtectedAssets = false // These items usually cannot be played back
        mediaPicker.showsCloudItems = false // MPMediaItems stored in the cloud don't have an assetURL
        mediaPicker.delegate = self
        mediaPicker.prompt = "Pick a track"
        present(mediaPicker, animated: true, completion: nil)
    }

    func startEngine(playFileAt: URL) {
        do {
            try AVAudioSession.sharedInstance().setCategory(.playback)

            let avAudioFile = try AVAudioFile(forReading: playFileAt)
            let player = AVAudioPlayerNode()

            engine.attach(player)
            engine.connect(player, to: engine.mainMixerNode, format: avAudioFile.processingFormat)

            try engine.start()
            player.scheduleFile(avAudioFile, at: nil, completionHandler: nil)
            player.play()
        } catch {
            assertionFailure(String(describing: error))
        }
    }
}

extension ViewController: MPMediaPickerControllerDelegate {
    func mediaPicker(_ mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {
        guard let item = mediaItemCollection.items.first else {
            print("no item")
            return
        }
        print("picking \(item.title!)")
        guard let url = item.assetURL else {
            return print("no url")
        }

        dismiss(animated: true) { [weak self] in
            self?.startEngine(playFileAt: url)
        }
    }

    func mediaPickerDidCancel(_ mediaPicker: MPMediaPickerController) {
        dismiss(animated: true, completion: nil)
    }
}