iPhone Read UIimage (frames) from video with AVFoundation

Question

Sorry for my english) Looking for information about read frames from a video with iPhone i found this project, http://www.codza.com/extracting-frames-from-movies-on-iphone/comment-page-1#comment-1116, but i also read somewhere that you can use AVFoundation to capture frames from a video for better performance..

But i can't find information of how i can do that...

Some idea?

Thanks for reading

Answer 1

You're talking about using the calls for generating what Apple calls thumbnail images from videos at specific times.

For an MPMoviePlayerController (what iOS uses to hold a video from a file or other source), there are two commands to do this. The first one generates a single thumbnail (image) from a movie at a specific point in time, and the second one generates a set of thumbnails for a time range.

This example gets an image at 10 seconds into a movie clip, myMovie.mp4:

MPMoviePlayerController *movie = [[MPMoviePlayerController alloc]
        initWithContentURL:[NSURL URLWithString:@"myMovie.mp4"]];
UIImage *singleFrameImage = [movie thumbnailImageAtTime:10 
        timeOption:MPMovieTimeOptionExact];

Note that this performs synchronously - i.e. the user will be forced to wait while you get the screenshot.

The other option is to get a series of images from a movie, from an array of times:

MPMoviePlayerController *movie = [[MPMoviePlayerController alloc]
        initWithContentURL [NSURL URLWithString:@"myMovie.mp4"]];
NSNumber time1 = 10;
NSNumber time2 = 11;
NSNumber time3 = 12;
NSArray *times = [NSArray arrayWithObjects:time1,time2,time3,nil];
[movie requestThumbnailImagesAtTimes:times timeOption:MPMovieTimeOptionExact];

This second way will trigger a notification of type MPMoviePlayerThumbnailImageRequestDidFinishNotification each time a new image is generated. You can set up an observer to monitor this and process the image - I'll leave you to work that bit out on your own!

Answer 2

You can also try AVAssetImageGenerator, specifically generateCGImagesAsynchronouslyForTimes:completionHandler.

This SO answer has good example code.

Answer 3

Swift 2 code to take frames with AVAssetImageGenerator:

func previewImageForLocalVideo(url:NSURL) -> UIImage?
{
    let asset = AVAsset(URL: url)
    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true

    var time = asset.duration
    //If possible - take not the first frame (it could be completely black or white on camara's videos)
    time.value = min(time.value, 2)

    do {
        let imageRef = try imageGenerator.copyCGImageAtTime(time, actualTime: nil)
        return UIImage(CGImage: imageRef)
    }
    catch let error as NSError
    {
        print("Image generation failed with error \(error)")
        return nil
    }
}

Answer 4

Here is code to get FPS images from video

1) Import

#import <Photos/Photos.h>

2) in viewDidLoad

    videoUrl = [NSURL fileURLWithPath:[[NSBundle mainBundle]pathForResource:@"VfE_html5" ofType:@"mp4"]];
    [self createImage:5]; // 5 is frame per second (FPS) you can change FPS as per your requirement.

3) Functions

-(void)createImage:(int)withFPS {
    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:videoUrl options:nil];
    AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
    generator.requestedTimeToleranceAfter =  kCMTimeZero;
    generator.requestedTimeToleranceBefore =  kCMTimeZero;

    for (Float64 i = 0; i < CMTimeGetSeconds(asset.duration) *  withFPS ; i++){
        @autoreleasepool {
            CMTime time = CMTimeMake(i, withFPS);
            NSError *err;
            CMTime actualTime;
            CGImageRef image = [generator copyCGImageAtTime:time actualTime:&actualTime error:&err];
            UIImage *generatedImage = [[UIImage alloc] initWithCGImage:image];
            [self savePhotoToAlbum: generatedImage]; // Saves the image on document directory and not memory
            CGImageRelease(image);
        }
    }
}

-(void)savePhotoToAlbum:(UIImage*)imageToSave {

    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        PHAssetChangeRequest *changeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:imageToSave];
    } completionHandler:^(BOOL success, NSError *error) {
        if (success) {
            NSLog(@"sucess.");
        }
        else {
            NSLog(@"fail.");
        }
    }];
}