iOS - How to play a video with transparency?

Question

Don't know if anyone is still interested in this besides me, but I'm using GPUImage and the Chromakey filter to achieve this^^ https://github.com/BradLarson/GPUImage

EDIT: example code of what I did (may be dated now):

-(void)AnimationGo:(GPUImageView*)view {
    NSURL *url = [[NSBundle mainBundle] URLForResource:@"test" withExtension:@"mov"];

    movieFile = [[GPUImageMovie alloc] initWithURL:url];
    filter = [[GPUImageChromaKeyBlendFilter alloc] init];

    [movieFile addTarget:filter];

    GPUImageView* imageView = (GPUImageView*)view;
    [imageView setBackgroundColorRed:0.0 green:0.0 blue:0.0 alpha:0.0];
    imageView.layer.opaque = NO;
    [filter addTarget:imageView];

    [movieFile startProcessing];

    //to loop
    [imageView setCompletionBlock:^{
        [movieFile removeAllTargets];
        [self AnimationGo:view];
    }];
}

I may have had to modify GPUImage a bit, and it may not work with the latest version of GPUImage but that's what we used

You'll need to build a custom player using AVFoundation.framework and then use a video with alpha channel. The AVFoundation framework allows much more robust handeling of video without many of the limitations of MPMedia framework. Building a custom player isn't as hard as people make it out to be. I've written a tutorial on it here: http://www.sdkboy.com/?p=66

I'm assuming what you're trying to do is actually remove the blue screen in real-time from your video: you'll need to play the video through OpenGL, run pixel shaders on the frames and finally render everything using an OpenGL layer with a transparent background.

See the Capturing from the Camera using AV Foundation on iOS 5 session from WWDC 2011 which explains techniques to do exactly that (watch Chroma Key demo at 9:00). Presumably the source can be downloaded but I can't find the link right now.

The GPUImage would work, but it is not perfect because the iOS device is not the place to do your video processing. You should do all your on the desktop using a professional video tool that handles chromakey, then export a video with an alpha channel. Then import the video into your iOS application bundle as described at playing-movies-with-an-alpha-channel-on-the-ipad. There are a lot of quality and load time issues you can avoid by making sure your video is properly turned into an alpha channel video before it is loaded onto the iOS device.