Xamarin.iOS AudioTrim Method

using System;
using System.IO;
using MonoTouch.Foundation;
using MonoTouch.AVFoundation;
using MonoTouch.CoreMedia;

namespace TestProject.Common
{
  public class AudioTrim
	{
		AVAsset _asset;
		AVAssetExportSession _exportSession;

		public AudioTrim ()
		{
		}

		public void TrimFile(string sourcePath, string exportPath, double stopTime, Action exportCompleted)
		{
			// Configure export
			_asset = AVAsset.FromUrl (NSUrl.FromFilename (sourcePath));
			_exportSession = new AVAssetExportSession ( _asset, AVAssetExportSession.PresetPassthrough);
			_exportSession.OutputUrl = NSUrl.FromFilename (exportPath);
			_exportSession.OutputFileType = AVFileType.Aiff;

			// Set range
			CMTimeRange range = new CMTimeRange();
			range.Start = CMTime.FromSeconds (0, _asset.Duration.TimeScale);
			range.Duration = CMTime.FromSeconds (stopTime, _asset.Duration.TimeScale);
			_exportSession.TimeRange = range;

			// Begin export
			_exportSession.ExportAsynchronously (new AVCompletionHandler(delegate {
				switch (_exportSession.Status) {
				case AVAssetExportSessionStatus.Failed:
					Console.WriteLine ("Export failed: {0}", _exportSession.Error.Description);
					break;
				case AVAssetExportSessionStatus.Cancelled:
					Console.WriteLine ("Export cancelled");
					break;
				case AVAssetExportSessionStatus.Completed:
					Console.WriteLine ("Export Completed");
					break;
				default:
					Console.WriteLine ("Export {0}", _exportSession.Status);
					break;
				}

				exportCompleted();
			}));
		}

		public void Dispose()
		{
			_asset.Dispose ();
			_exportSession.Dispose ();
		}
	}
}