AudioSplitter.swift

import Foundation
import Foundation
import AVFoundation

class AudioSplitter {
    
    var filePrepend: String = "file://"
    var fileSeparator: Character = "."
    var fileSplitAppend: String = "-split-"
    
    func splitAudio(asset: AVAsset, segment: Int, splitSourceFileURL: Array<Substring>) {
        // Create an output exporter (hardcoded to m4a)
        let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetAppleM4A)!
        exporter.outputFileType = AVFileType.m4a
      
        // Only export for within this time range
        let startTime = CMTimeMake(value: Int64(5 * 60 * segment), timescale: 1)
        let endTime = CMTimeMake(value: Int64(5 * 60 * (segment+1)), timescale: 1)

        exporter.timeRange = CMTimeRangeFromTimeToTime(start: startTime, end: endTime)

        /**
            Output file format:
         
                originalFile-split-1.m4a
                originalFile-split-2.m4a
         
            Etc...
         */
        let outputFileURL = URL(string: "\(filePrepend)\(splitSourceFileURL[0])\(fileSplitAppend)\(segment)\(fileSeparator)\(splitSourceFileURL[1])")!
        
        exporter.outputURL = outputFileURL
        
        // Do the export
        exporter.exportAsynchronously(completionHandler: {
            switch exporter.status {
                case AVAssetExportSession.Status.failed:
                    print("Export failed.")
                    if let e = exporter.error {
                        print(e)
                    }
                case AVAssetExportSession.Status.cancelled:
                    print("Export cancelled.")
                default:
                    print("Export complete.")
            }
        })
        return
    }
    
    public func processAudio(sourceFileURL: String) {
        // Original file as URL
        let fileURL: URL = URL(string: "\(filePrepend)\(sourceFileURL)")!
        // Original file as AVAsset
        let asset: AVAsset = AVAsset(url: fileURL)

        let splitSourceFileURL = sourceFileURL.split(separator: fileSeparator)

        // Length of original file
        let duration = CMTimeGetSeconds(asset.duration)
        
        let numOfSegments = Int(ceil(duration / 300) - 1)
        
        for index in 0...numOfSegments {
            splitAudio(asset: asset, segment: index, splitSourceFileURL: splitSourceFileURL)
        }
            
        return
    }

}