视频关键帧的获取

代码如下:

导入框架:#import <AVFoundation/AVFoundation.h>
atTime表示在什么时刻，取值范围0-1

//获取指定的视频帧
+ (void)getVideoFrameWith:(NSURL *)fileUrl
                        atTime:(CGFloat)atTime
                         block:(void(^)(UIImage *image))block
                     fail:(void(^)(NSString *error))fail {
    
    if (!fileUrl) return;
    
    AVAsset *asset = [AVAsset assetWithURL:fileUrl];
    AVAssetImageGenerator *imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
    
    CGFloat totalTime = asset.duration.value / asset.duration.timescale;
    if (totalTime < 0) {
        fail(@"视频总时长小于0");
        return;
    }
    
    //如果不设置这两个属性为kCMTimeZero，则实际生成的图片和需要生成的图片会有时间差
    imageGenerator.requestedTimeToleranceBefore = kCMTimeZero;
    imageGenerator.requestedTimeToleranceAfter = kCMTimeZero;
    
    imageGenerator.appliesPreferredTrackTransform = YES;    //截图的时候调整到正确的方向
    
    CGFloat value = totalTime * atTime;    //第几秒
    CGFloat timeScale = asset.duration.timescale; //帧率
    
    value = MAX(value, 0);
    value = MIN(value, asset.duration.value);
    
    CMTime requestTime = CMTimeMakeWithSeconds(value, timeScale);   //时间
    
    NSError *error = nil;
    CGImageRef imageRef = [imageGenerator copyCGImageAtTime:requestTime actualTime:NULL error:&error];
    if (error) {
        fail(error.debugDescription);
    }else {
        UIImage *img = [UIImage imageWithCGImage:imageRef];
        dispatch_async(dispatch_get_main_queue(), ^{
            if (block) {
                block(img);
            }
        });
    }
    
}

GitHub链接