我希望用户从他的库中选择一个视频，并将其限制为45秒（像WhatsApp -您可以编辑视频，将被发送的视频不超过45秒。
但是如果我使用下面的代码，它会选择一个视频，而不管它的持续时间，我不能修剪它（用一个视频测试，长度为1分钟）

UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init];
        imagePickerController.delegate = self; 
        imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        imagePickerController.videoQuality = UIImagePickerControllerQualityTypeLow;
        imagePickerController.videoMaximumDuration = 45.0f; //?
        imagePickerController.mediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypePhotoLibrary];

        [[self parentViewController] presentModalViewController:imagePickerController animated:YES];
        [imagePickerController release];

在WhatsApp中，我得到以下屏幕，我想重现：