AVAudioPlayer没有播放任何东西。

Question

我有一个tableViewCell，我想在其中播放典型的.m4a声音。 我已经像这样全局声明了我的AVAudioPlayer实例：

var player = AVAudioPlayer()

然后我下载了我的音频文件，并将其放置在“文档”目录下的一个文件夹中。但是，当我尝试从该文件夹播放我的音频文件时，出现以下错误：

Open failed
The operation couldn’t be completed. (OSStatus error 2003334207.)

这是我的代码，我不知道哪里有问题。我在模拟器中找到了这些文件，可以用QuickTimePlayer播放。

func downloadSound(_ message: ChatVoiceMessageStructure) {
    guard let url = service?.networkManager.CDNURL else { return }
    let doanloadURL = URL(string: url.appending(message.name!))
    let docUrl:URL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first as URL!
    let desURL = docUrl.appendingPathComponent("tmpsong.m4a")
    var downloadTask:URLSessionDownloadTask
    let request = URLRequest(url: doanloadURL!)
    downloadTask = URLSession.shared.downloadTask(with: request, completionHandler: { [weak self](URLData, response, error) -> Void in
        do{
            let isFileFound:Bool? = FileManager.default.fileExists(atPath: desURL.path)
            if isFileFound == true{
                print(desURL) //delete tmpsong.m4a & copy
            } else {
                try FileManager.default.copyItem(at: URLData!, to: desURL)
            }
            let sPlayer = try AVAudioPlayer(contentsOf: desURL)
            self?.player = sPlayer
            self?.player.prepareToPlay()
            self?.player.play()

        } catch let err {
            print(err.localizedDescription)
        }

    })
    downloadTask.resume()

}

- tara tandel

Answer 1

我最终在Mahipal的帮助下找到了问题的解决方法。问题是AVAudioPlayer无法播放某些音频格式，例如音频扩展名为MPEG4但音频编码不是AAC。因此，请注意AVAudioPlayer支持的格式。您可以在CoreAudio类及其AudioFormatID子类中找到这些格式。这花费了我数周的时间来解决，希望可以节省他人的时间。 如果您想播放其他类型的音频，可以使用AVPlayer。

以下是供以后参考的类型：

public var kAudioFormatLinearPCM: AudioFormatID { get }
public var kAudioFormatAC3: AudioFormatID { get }
public var kAudioFormat60958AC3: AudioFormatID { get }
public var kAudioFormatAppleIMA4: AudioFormatID { get }
public var kAudioFormatMPEG4AAC: AudioFormatID { get }
public var kAudioFormatMPEG4CELP: AudioFormatID { get }
public var kAudioFormatMPEG4HVXC: AudioFormatID { get }
public var kAudioFormatMPEG4TwinVQ: AudioFormatID { get }
public var kAudioFormatMACE3: AudioFormatID { get }
public var kAudioFormatMACE6: AudioFormatID { get }
public var kAudioFormatULaw: AudioFormatID { get }
public var kAudioFormatALaw: AudioFormatID { get }
public var kAudioFormatQDesign: AudioFormatID { get }
public var kAudioFormatQDesign2: AudioFormatID { get }
public var kAudioFormatQUALCOMM: AudioFormatID { get }
public var kAudioFormatMPEGLayer1: AudioFormatID { get }
public var kAudioFormatMPEGLayer2: AudioFormatID { get }
public var kAudioFormatMPEGLayer3: AudioFormatID { get }
public var kAudioFormatTimeCode: AudioFormatID { get }
public var kAudioFormatMIDIStream: AudioFormatID { get }
public var kAudioFormatParameterValueStream: AudioFormatID { get }
public var kAudioFormatAppleLossless: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_HE: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_LD: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_ELD: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_ELD_SBR: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_ELD_V2: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_HE_V2: AudioFormatID { get }
public var kAudioFormatMPEG4AAC_Spatial: AudioFormatID { get }
public var kAudioFormatAMR: AudioFormatID { get }
public var kAudioFormatAMR_WB: AudioFormatID { get }
public var kAudioFormatAudible: AudioFormatID { get }
public var kAudioFormatiLBC: AudioFormatID { get }
public var kAudioFormatDVIIntelIMA: AudioFormatID { get }
public var kAudioFormatMicrosoftGSM: AudioFormatID { get }
public var kAudioFormatAES3: AudioFormatID { get }
public var kAudioFormatEnhancedAC3: AudioFormatID { get }
public var kAudioFormatFLAC: AudioFormatID { get }
public var kAudioFormatOpus: AudioFormatID { get }

- tara tandel

Answer 2

请在真实设备上运行，并在URLSession块中添加DispatchQueue.main.async。

这里我稍微修改了您的代码，在真实设备上运行成功...

var audioPlayer:AVAudioPlayer!
    func downloadSound() {
        let doanloadURL = URL(string: "https://github.com/robovm/apple-ios-samples/raw/master/avTouch/sample.m4a")!
        let docUrl:URL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
        let desURL = docUrl.appendingPathComponent("sample.m4a")
        var downloadTask:URLSessionDownloadTask
        let request = URLRequest(url: doanloadURL)
        downloadTask = URLSession.shared.downloadTask(with: request, completionHandler: { (URLData, response, error) -> Void in
            DispatchQueue.main.async {
                do{
                    let isFileFound:Bool? = FileManager.default.fileExists(atPath: desURL.path)
                    if isFileFound == true{
                        print(desURL) //delete tmpsong.m4a & copy
                    } else {
                        try FileManager.default.copyItem(at: URLData!, to: desURL)
                    }
                     let sPlayer = try AVAudioPlayer(contentsOf: desURL)
                    try AVAudioSession.sharedInstance().setCategory(.playback, mode: .default)
                    try AVAudioSession.sharedInstance().setActive(true)
                    self.audioPlayer = sPlayer
                    self.audioPlayer.prepareToPlay()
                    self.audioPlayer.play()
                  } catch let err {
                    print(err.localizedDescription)
                }
            }
         })
        downloadTask.resume()
     }

- MAhipal Singh

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我已经尝试过了，但仍然没有机会。我忘了说所有文件的扩展名都是.m4a。也许这有问题？ - tara tandel

@taratandel的回答已经更新，使用.m4a扩展名。请尝试，如果仍然有问题，请分享您的URL进行测试？ - MAhipal Singh

这是URL地址：http://kise.roo.cloud/uz-chat/42df4188-e828-11e8-a2e4-e0071bf7f949.m4a - tara tandel

@tara 你的文件可能有问题。我甚至尝试过使用 Bundle 路径，但是出现了同样的错误。当我尝试下面的 iTunes 链接时，代码可以正常工作。https://audio-ssl.itunes.apple.com/apple-assets-us-std-000001/AudioPreview18/v4/9c/db/54/9cdb54b3-5c52-3063-b1ad-abe42955edb5/mzaf_520282131402737225.plus.aac.p.m4a - MAhipal Singh