Playing iPod Library songs using CocosDenshion

Question

I am trying to let the user select a song from the iPod Library. After getting the song URL from that, I am trying to play it using the CocosDenshion library but I am not getting any sound.

Here's the code sample of MPMediaPickerControllerDelegate:

#pragma mark MPMediaPickerControllerDelegate
- (void)mediaPicker: (MPMediaPickerController *)mediaPicker
  didPickMediaItems:(MPMediaItemCollection *)mediaItemCollection {
    [self dismissModalViewControllerAnimated:YES];
    if ([mediaItemCollection count] < 1) {
        return;
    }
    [song release];
    song = [[[mediaItemCollection items] objectAtIndex:0] retain];


    NSURL *itemURL = [song valueForProperty:MPMediaItemPropertyAssetURL];
    fileURL = [itemURL absoluteString];

    [[SimpleAudioEngine sharedEngine] preloadEffect:fileURL];
}

and here's the handler for the button that plays the sound.

- (IBAction)playSong {

    [[SimpleAudioEngine sharedEngine] playEffect:fileURL pitch:1.0f pan:0.0f gain:1.0f];
}

Can anyone tell me what is going wrong. I need to be able to change the pitch of the selected song. That is why I am using CocosDenshion library.

Answer 1

Have a look at the URL returned by [song valueForProperty:MPMediaItemPropertyAssetURL] in the debugger. It is not a standard file system URL but a custom URL that points into the asset library so it is no wonder CocosDenshion can't open it.

You will need to use AV Foundation (probably AVAudioPlayer) to play the song. Or use AV Foundation to first convert the song into a "real" file and then play it back with Cocos Denshion but that is probably much more complicated than the first option.

The documentation for MPMediaItemPropertyAssetURL clearly says so, too:

Usage of the URL outside of the AV Foundation framework is not supported.