{
NSURL *assetURL = [NSURL URLWithString:_assertURL];
    AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL:assetURL options:nil];

    /* approach 1: export just the song itself
     */
    AVAssetExportSession *exporter = [[AVAssetExportSession alloc]
                                      initWithAsset: songAsset
                                      presetName: AVAssetExportPresetAppleM4A];
    NSLog (@"created exporter. supportedFileTypes: %@", exporter.supportedFileTypes);
    exporter.outputFileType = @"com.apple.m4a-audio";
    NSString *exportFile = [myDocumentsM4aDirectory() stringByAppendingPathComponent: [NSString stringWithFormat:@"%@.m4a",_title]];
    // end of approach 1

    // set up export (hang on to exportURL so convert to PCM can find it)
    [self myDeleteFile:exportFile];
    //[exportURL release];
    _exportURL = [NSURL fileURLWithPath:exportFile];
    exporter.outputURL = _exportURL;

    // do the export
    [exporter exportAsynchronouslyWithCompletionHandler:^{
        int exportStatus = exporter.status;
        switch (exportStatus) {
            case AVAssetExportSessionStatusFailed: {
                // log error to view
                NSError *exportError = exporter.error;
                NSLog (@"AVAssetExportSessionStatusFailed: %@", exportError);

                break;
            }
            case AVAssetExportSessionStatusCompleted: {
                NSLog (@"AVAssetExportSessionStatusCompleted");

 //Final document url

                NSURL *audioUrl = _exportURL;
                NSLog(@"Audio Url=%@",audioUrl);


                break;
            }
            case AVAssetExportSessionStatusUnknown: {
                NSLog (@"AVAssetExportSessionStatusUnknown");


                break;
            }
            case AVAssetExportSessionStatusExporting: {
                NSLog (@"AVAssetExportSessionStatusExporting");


                break;
            }
            case AVAssetExportSessionStatusCancelled: {
                NSLog (@"AVAssetExportSessionStatusCancelled");


                break;
            }
            case AVAssetExportSessionStatusWaiting: {
                NSLog (@"AVAssetExportSessionStatusWaiting");

                break;
            }
            default: {
                NSLog (@"didn't get export status");


                break;
            }
        }
    }];

}

- (void)myDeleteFile:(NSString*)path{

    if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
        NSError *deleteErr = nil;
        [[NSFileManager defaultManager] removeItemAtPath:path error:&deleteErr];
        if (deleteErr) {
            NSLog (@"Can't delete %@: %@", path, deleteErr);
        }
    }

}

NSString* myDocumentsM4aDirectory(){

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSError *error = nil;
    NSString *dataPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"/m4aFolder"];

    if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
        [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:&error];
    //Create folde
    return dataPath;


}