Using MPMediaItem with simpleaudioengine

I've been making a project in cocos-2dx, but needed to create a .mm to select music from the iOS library to play in the background. I got it working by playing the music in the .mm file, but for various reasons, it needs to play in cocos-2dx using SimpleAudioEngine. I've tried converting the url's absoluteString to an NSString to an id to a const char* to move it back to the cocos-2dx files, but it still didn't run.

This is what it gave me for the absoluteString(ipod-library://item/item.m4a?id=456458322781804615)

.cc-

-(void)mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:(MPMediaItemCollection *)collection{
if(collection){
    MPMusicPlayerController* appMusicPlayer = [MPMusicPlayerController applicationMusicPlayer];
    [appMusicPlayer setQueueWithItemCollection:collection];
    [appMusicPlayer play];
    MPMusicPlayerController *iPodMusicPlayerController = [MPMusicPlayerController iPodMusicPlayer];
    MPMediaItem *nowPlayingItem = [iPodMusicPlayerController nowPlayingItem];

    NSURL *url = [nowPlayingItem valueForProperty:MPMediaItemPropertyAssetURL];
    NSString *filePath= [url absoluteString];
    NSString *filePath2 = [url path];
    _songUrl = filePath;
 }
 -(id)returnsongUrl{
     return _songUrl;
 }

Second .mm

 const char* MediaPicker::songUrl(){
     id na1 = [[MediaPickerWrapper sharedIntance] returnsongUrl];
    const char *cString =  [na1 cStringUsingEncoding:NSASCIIStringEncoding];
    return  cString;
 }

Cocos-2dx file

  CocosDenshion::SimpleAudioEngine::sharedEngine()->preloadBackgroundMusic(media->songUrl());
  CocosDenshion::SimpleAudioEngine::sharedEngine()->playBackgroundMusic(media->songUrl(),false);