.band 文件已损坏或 swift 中的文件格式不正确

Question

我尝试将音频导出为 .band 文件，但 GarageBand 表示文件已损坏或格式不正确

func copyAudioFileToDocuments(ringtone: Ringtone?) async throws -> URL? {
        guard let ringtone, let documentsURL = ringtone.url else { return nil }
                
        
        let asset = AVURLAsset(url: documentsURL)
        let exportAudioMix = AVMutableAudioMix()
        
        guard let track = try await asset.load(.tracks).last else { return nil }

        let start = ringtone.info.startTime
        let length = ringtone.info.endTime - ringtone.info.startTime
        
        let exportTimeRange = CMTimeRange(start: .init(seconds: start, preferredTimescale: 1),
                                          duration: .init(seconds: length, preferredTimescale: 1))

        
        let destinationURL = Constants.cachesDirectory.appendingPathComponent(ringtone.id.replacingOccurrences(of: ringtone.info.title.ext.rawValue, with: "band"))
        try await exportAudio(from: track, mix: exportAudioMix, exportTimeRange: exportTimeRange, to: destinationURL)
        return destinationURL
    }

------------------->
func exportAudio(from track: AVAssetTrack, mix: AVAudioMix? = nil, exportTimeRange: CMTimeRange? = nil, to destinationURL: URL) async throws {
        let composition = AVMutableComposition()
        let compositionAudioTrack = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)
        let duration = try await track.asset?.load(.duration)
        try compositionAudioTrack?.insertTimeRange(CMTimeRangeMake(start: .zero, duration: duration ?? .init()), of: track, at: .zero)
        
        let exportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetPassthrough)
        if let exportTimeRange { exportSession?.timeRange = exportTimeRange }
        exportSession?.outputURL = destinationURL
        exportSession?.audioMix = mix
        exportSession?.outputFileType = AVFileType.aiff
        if FileManager.default.fileExists(atPath: destinationURL.path) {
            try FileManager.default.removeItem(at: destinationURL)
        }
        try await exportSession?.exportAsync()
    }

我尝试使用 .mp3 扩展名，一切正常，但使用 .band 则无法正常工作。

Answer 1

.band 文件实际上并不是声音文件。它根本不是一个文件。它是（正如您在评论中已经被告知的那样）一个包，即伪装成文件的文件夹；该文件夹内是整个 GarageBand 项目。如何正确构建文件夹的内容取决于you； AVAssetExportSession 不会神奇地为您制作一个。