iOS 获取视频某一帧图像

-(UIImage*)getCoverImage{

    AVURLAsset *asset = [[AVURLAssetalloc] initWithURL:_outMovieURLoptions:nil];

    NSParameterAssert(asset);

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

    assetImageGenerator.appliesPreferredTrackTransform =YES;

    assetImageGenerator.apertureMode =AVAssetImageGeneratorApertureModeEncodedPixels;

    

    CGImageRef thumbnailImageRef = NULL;

    NSError *thumbnailImageGenerationError = nil;

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

    

    if (!thumbnailImageRef)

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

    

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

    return thumbnailImage;

}