Here is how to create thumbnail for videos. Two steps:

  1. Use AVURLAsset to access to the video file by URL. Then use AVAssetImageGenerator to generate an image of one frame.
  2. To distinguish the image we generated from normal images, add a play icon on the top of the image by merging two UIImage .

Code:

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+ (UIImage *)createVideoThumbnailWithPath:(NSString *)videoPath {
    if (!videoPath)
        return nil;

    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:videoPath] options:nil];
    AVAssetImageGenerator *imgGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
    imgGenerator.appliesPreferredTrackTransform = YES;
    imgGenerator.apertureMode = AVAssetImageGeneratorApertureModeEncodedPixels;

    // create CGImage
    CGImageRef thumbnailImgRef = nil;
    // the time frame
    CFTimeInterval thumbnailImageTime = 0;
    NSError *error = nil;

    // get the image
    thumbnailImgRef = [imgGenerator copyCGImageAtTime:CMTimeMake(thumbnailImageTime, 60) actualTime:nil error:&error];

    // error handling
    if (!thumbnailImgRef)
        NSLog(@"VIDEO THUMBNAIL ERROR: %@", error);

    // convert to UIImage
    UIImage *image = thumbnailImgRef ? [[UIImage alloc] initWithCGImage:thumbnailImgRef] : nil;

    // add playIcon
    if (image) {
        // grab your play icon
        UIImage *playIcon = [UIImage imageNamed:@"PlayIcon"];

        // start image context
        UIGraphicsBeginImageContext(image.size);

        // add original image first with existing opacity
        [image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];

        // add play icon over the image in the middle with supplied opacity if applicable
        [playIcon drawInRect:CGRectMake((image.size.width - playIcon.size.width) / 2.0,
                                        (image.size.height - playIcon.size.height) / 2.0,
                                        playIcon.size.width,playIcon.size.height)
                   blendMode:kCGBlendModeNormal
                       alpha:0.9];

        // get merged image
        UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();

        return newImage;
    }
    return image;
}