AVAudioSession crashing in new Thread - ios

Question

I have a Method wich create an UIScrollView and your subviews programmatically. One of your views is a MoviewPlayer...While the scrollview is being created, I need to allow the user to exit the screen (before the loading ends). Then, I've called this method in another NSThread.
But I'm getting the following error:
[__NSCFData _pickableRoutesDidChangeNotification:]: unrecognized selector sent to instance
I think it's not possible to do it in another Thread. Then, How could I allow the user to exit the view before the loading ends?
Theres my code:
-(void) viewDidAppear:(BOOL)animated {
[NSThread detachNewThreadSelector:#selector(criarScrollMidias:) toTarget:self withObject:self.eventoAtual];
}
-(void) criarScrollMidias:(Evento *)evento {
NSLog(#"criar scroll midias");
NSMutableArray *listaImagens = evento.atracao.images;
NSMutableArray *listaVideos = evento.atracao.videos;
if([listaVideos count] > 0) {
self.listaVideoPlayers = [[NSMutableArray alloc]init];
}
[self.scrollImVd setPagingEnabled:YES];
if(![self.eventoAtual.atracao.imageLarge isKindOfClass:[NSNull class]])
{
UIImageView *imgViewAtracao = [[UIImageView alloc]initWithImage:self.eventoAtual.atracao.imageLarge];
[imgViewAtracao setContentMode:UIViewContentModeScaleAspectFit];
[imgViewAtracao setFrame:CGRectMake(0, 0, self.scrollImVd.frame.size.width, self.scrollImVd.frame.size.height)];
[self.scrollImVd addSubview:imgViewAtracao];
}
for (int iCnt = 0; iCnt < [listaImagens count]; iCnt++) {
NSString *imgURL = [listaImagens objectAtIndex:iCnt];
UIImage *imagemAtracao = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imgURL]]];
UIImageView *imgViewAtracao = [[UIImageView alloc]initWithImage:imagemAtracao];
[imgViewAtracao setContentMode:UIViewContentModeScaleAspectFit];
if(![self.eventoAtual.atracao.imageLarge isKindOfClass:[NSNull class]])
[imgViewAtracao setFrame:CGRectMake(0+self.scrollImVd.frame.size.width*(iCnt+1), 0, self.scrollImVd.frame.size.width, self.scrollImVd.frame.size.height)];
else
[imgViewAtracao setFrame:CGRectMake(0+self.scrollImVd.frame.size.width*iCnt, 0, self.scrollImVd.frame.size.width, self.scrollImVd.frame.size.height)];
[self.scrollImVd addSubview:imgViewAtracao];
}
for (int iCnt = 0; iCnt < [listaVideos count]; iCnt++) {
NSString *videoURLStr = [listaVideos objectAtIndex:iCnt];
NSURL *videoURL = [NSURL URLWithString:videoURLStr];
MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:videoURL];
moviePlayer.movieSourceType = MPMovieSourceTypeStreaming;
[moviePlayer setShouldAutoplay:NO];
[moviePlayer.view setBackgroundColor:[UIColor colorWithPatternImage:[self gerarPreviewVideo:videoURL]]];
CGFloat posicaoInicial = 0.0;
if(![self.eventoAtual.atracao.imageLarge isKindOfClass:[NSNull class]])
posicaoInicial = self.scrollImVd.frame.size.width * ([listaImagens count] + 1);
else
posicaoInicial = self.scrollImVd.frame.size.width * [listaImagens count];
[moviePlayer.view setFrame:CGRectMake(posicaoInicial+self.scrollImVd.frame.size.width*iCnt, 0, self.scrollImVd.frame.size.width, self.scrollImVd.frame.size.height)];
UIButton *playButton = [[UIButton alloc] initWithFrame:CGRectMake(moviePlayer.view.frame.origin.x+(self.scrollImVd.frame.size.width/2)-34, moviePlayer.view.frame.origin.y+(self.scrollImVd.frame.size.height/2)-33, 67, 66)];
[playButton setImage:[UIImage imageNamed:#"play.png"] forState:UIControlStateNormal];
playButton.tag = iCnt;
[playButton addTarget:self action:#selector(playButtonClick:) forControlEvents:UIControlEventTouchUpInside];
[self.scrollImVd addSubview:moviePlayer.view];
[self.scrollImVd addSubview:playButton];
[self.listaVideoPlayers addObject:moviePlayer];
}
if(![self.eventoAtual.atracao.imageLarge isKindOfClass:[NSNull class]])
[self.scrollImVd setContentSize:CGSizeMake(self.scrollImVd.frame.size.width * ([listaImagens count] + [listaVideos count] + 1), self.scrollImVd.frame.size.height)];
else
[self.scrollImVd setContentSize:CGSizeMake(self.scrollImVd.frame.size.width * ([listaImagens count] + [listaVideos count]), self.scrollImVd.frame.size.height)];
[self.viewLoading setHidden:YES];
}
I've debugged and discovered that the problem is when I try to generate the preview in another Thread:
-(UIImage *) gerarPreviewVideo:(NSURL *)videoURL {
AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];
AVAssetImageGenerator *generateImg = [[AVAssetImageGenerator alloc] initWithAsset:asset];
NSError *error = NULL;
CMTime time = CMTimeMake(1, 65);
CGImageRef refImg = [generateImg copyCGImageAtTime:time actualTime:NULL error:&error];
UIImage *thumbnail= [[UIImage alloc] initWithCGImage:refImg];
return thumbnail;
}
How could I resolve it?