MPMoviePlayerController generate thumbnail of local video file and store it - objective-c

Question

I'm making an app that downloads movies from the server and stores them localy in the NSDocumentDirectory.
This works fine.
I want to add a thumbnail generated from each movie in front of the name in each cell.
My problem:
How can I generate a thumbnail from a movie after it is downloaded (so instantly, without having to play the movie first)? I want to store the thumbnails with the same name of the movie as a jpg in the NSDocumentDirectory.
My guess
-download movie and store it in NSDocumentDirectory (works)
-somehow load the movie in the MPMoviePlayerController's memory (don't know how)
-when loaded in memory, generate thumbnail with thumbnailImageAtTime (MPMovieTimeOptionNearestKeyFrame) (should work)
-store it (should work)
If anyone could help me...
Thanks

Answer 1

#import <MediaPlayer/MediaPlayer.h>
-(UIImage*)getFirstFrameFromVideoFile:(NSString*)sourceFilePath {
NSURL *videoURL = [NSURL fileURLWithPath:sourceFilePath];
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:videoURL];
UIImage *thumbnail = [player thumbnailImageAtTime:1.0 timeOption:MPMovieTimeOptionNearestKeyFrame];
//Player autoplays audio on init
[player stop];
[player release];
return thumbnail;
}
Other tasks you know already.

Answer 2

Yes, using MPMoviePlayer works... but you must be sure that you do not have another movie player playing elsewhere in your app (even the UIWebView plug-in...) or you will get in trouble.
I do this way:
UIImage *thumbnail = nil;
NSURL *url = [NSURL fileURLWithPath:pathname];
AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:url options:nil];
AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
generator.appliesPreferredTrackTransform = YES;
NSError *error = nil;
CMTime time = CMTimeMake(3, 1); // 3/1 = 3 second(s)
CGImageRef imgRef = [generator copyCGImageAtTime:time actualTime:nil error:&error];
if (error != nil)
NSLog(#"%#: %#", self, error);
thumbnail = [[UIImage alloc] initWithCGImage:imgRef];
CGImageRelease(imgRef);
Hope this might help

Answer 3

This is the code I use which should generate the thumbnail
(added a big uiimageview for testing, works when I load a local image in it)
NSString *path;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
path = [[paths objectAtIndex:0] stringByAppendingPathComponent:#"snijtechniekendir/videos"];
path = [path stringByAppendingPathComponent:[videos objectAtIndex:indexPath.row]];
NSURL *videoURL = [NSURL fileURLWithPath:path];
NSLog(#"video url: %#", videoURL);
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:videoURL];
UIImage *thumbnail = [player thumbnailImageAtTime:1 timeOption:MPMovieTimeOptionNearestKeyFrame];
UIImageView *cellimage = [[UIImageView alloc] initWithFrame:CGRectMake(2, 2 , 400, 400)];
[cell.contentView addSubview:cellimage];
NSData *imgData = UIImagePNGRepresentation(thumbnail);
NSLog(#"lenght of video thumb: %#", [imgData length]);
[self.view addSubview:cellimage];
[cellimage setImage:thumbnail];
This is the log for one video file
video url: file://localhost/Users/Home/Library/Application%20Support/iPhone%20Simulator/5.1/Applications/78C165BB-75A9-46A2-A257-469F8652A665/Documents/snijtechniekendir/videos/snijtechniek%2520brunoise.mp4
lenght of video thumb: (null)