iOS 获取视频某一帧图像

-(UIImage*)getCoverImage{

    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:_outMovieURL options:nil];

    NSParameterAssert(asset);

    AVAssetImageGenerator *assetImageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];

    assetImageGenerator.appliesPreferredTrackTransform = YES;

    assetImageGenerator.apertureMode = AVAssetImageGeneratorApertureModeEncodedPixels;

    

    CGImageRef thumbnailImageRef = NULL;

    NSError *thumbnailImageGenerationError = nil;

    thumbnailImageRef = [assetImageGenerator copyCGImageAtTime:CMTimeMake(2*15, 15) actualTime:NULL error:&thumbnailImageGenerationError];

    

    if (!thumbnailImageRef)

        NSLog(@"thumbnailImageGenerationError %@", thumbnailImageGenerationError);

    

    UIImage *thumbnailImage = thumbnailImageRef ? [[UIImage alloc] initWithCGImage:thumbnailImageRef] : nil;

    return thumbnailImage;

}