#pragma mark - 网络视频预览

- (void)getEachPic {

    AVAsset *myAsset = [AVAsset assetWithURL:pathURL];

    AVAssetImageGenerator *imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:myAsset];

    imageGenerator.appliesPreferredTrackTransform = YES;

    imageGenerator.requestedTimeToleranceAfter = kCMTimeZero;

    Float64 durationSeconds = CMTimeGetSeconds([myAsset duration]);

    NSMutableArray *timesArr = [[NSMutableArray alloc] init];

    int totalSec = durationSeconds; 

    for (int i=0; i<totalSec;i++){

        int sec = durationSeconds/totalSec * i;

        CMTime firstThird = CMTimeMakeWithSeconds(sec, 20);

        NSValue *value = [NSValue valueWithCMTime:firstThird];

        [timesArr addObject:value];

    }

     __block NSInteger index = 0;

    [imageGenerator generateCGImagesAsynchronouslyForTimes:timesArr completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error) {

        NSString *requestedTimeString = (NSString *) CFBridgingRelease(CMTimeCopyDescription(NULL, requestedTime));

        NSString *actualTimeString = (NSString *) CFBridgingRelease(CMTimeCopyDescription(NULL, actualTime));                

        NSLog(@"Requested: %@; actual %@", requestedTimeString, actualTimeString);     

        if (result == AVAssetImageGeneratorSucceeded) {

                // Do something interesting with the image.

                index ++;

                UIImage *imageData = [[UIImage alloc] initWithCGImage:image];

                 dispatch_async(dispatch_get_main_queue(), ^{

                        // 获取到图片，在主线程中刷新界面

                });

        } else if (result == AVAssetImageGeneratorCancelled) {

                NSLog(@"Canceled");

        } else if (result == AVAssetImageGeneratorFailed) {

                NSLog(@"Failed with error: %@", [error localizedDescription]);

        }

    }];

}