Objective c AVCaptureStillImageOutput缺少元数据

我使用以下代码捕获图像：

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageSampleBuffer, NSError *error) {
     CFDictionaryRef exifAttachments = CMGetAttachment(imageSampleBuffer, kCGImagePropertyExifDictionary, NULL);
     NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
     UIImage *image = [[UIImage alloc] initWithData:imageData];
     NSDictionary *metadata = (__bridge NSDictionary*)exifAttachments;
     NSLog(@"%@",metadata");
}];

以下是记录的输出：

ApertureValue = "2.526068811667588";
BrightnessValue = "-0.5270684580355165";
ExposureMode = 0;
ExposureProgram = 2;
ExposureTime = "0.06666666666666667";
FNumber = "2.4";
Flash = 16;
FocalLenIn35mmFilm = 35;
FocalLength = "4.28";
ISOSpeedRatings =     (
    500
);
MeteringMode = 5;
PixelXDimension = 3264;
PixelYDimension = 2448;
SceneType = 1;
SensingMethod = 2;
ShutterSpeedValue = "3.906905022631062";
SubjectArea =     (
    1631,
    1223,
    881,
    881
);
WhiteBalance = 0;

---

为什么我没有得到任何与时间相关的元数据？我想知道图像是什么时候拍摄的。

我确定，在将日期和时间添加到相机卷后，该日期和时间会添加到元数据中（开发人员没有做任何工作）。无需担心信息丢失

我是否需要自己添加“kCGImagePropertyExifDateTimeOriginal”值？似乎有点违反直觉。。。