ios截取视频缩略图

        AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:path options:nil];        AVAssetImageGenerator *gen = [[AVAssetImageGenerator alloc] initWithAsset:asset];        gen.appliesPreferredTrackTransform = YES;        CMTime time = CMTimeMakeWithSeconds(0.0, 600);        NSError *error = nil;        CMTime actualTime;            CGImageRef image = [gen copyCGImageAtTime:time actualTime:&actualTime error:&error];        UIImage *thumb = [[UIImage alloc] initWithCGImage:image];        CGImageRelease(image);        _videoPreview.previewImageView.image = thumb;        _videoPreview.videoURL = path;