我使用此代码从相机捕获视频，但CMSampleBufferGetImageBuffer(sampleBuffer)始终返回nil。问题是什么？。这是代码，我修改了此源代码以适应Swift4https://github.com/FlexMonkey/CoreImageHelpers/blob/master/CoreImageHelpers/coreImageHelpers/CameraCaptureHelper.swiftimportAVFoundationimportCoreMediaimportCoreImageimportUIKitclassCameraCaptureHelper:

我每N个视频帧从CMSampleBufferRef视频缓冲区获取一个UIImage，例如:-(void)imageFromVideoBuffer:(void(^)(UIImage*image))completion{CMSampleBufferRefsampleBuffer=_myLastSampleBuffer;if(sampleBuffer!=nil){CFRetain(sampleBuffer);CIImage*ciImage=[CIImageimageWithCVPixelBuffer:CMSampleBufferGetImageBuffer(sampleBuffer)];_l