Webrtc IOS - 当我将分辨率设置为1080P时，我得到黑屏

Question

当我将RTC Media Constraints设置为1080P时，我会出现黑屏：
In this Project

 - (RTCMediaConstraints *)defaultMediaStreamConstraints {

RTCPair *minWidth = [[RTCPair alloc] initWithKey:@"minWidth"  value:@"1920"];

RTCPair *minHeight = [[RTCPair alloc] initWithKey:@"minHeight" value:@"1080"];

NSArray *mandatory = @[ minWidth ,minHeight];



RTCMediaConstraints *constraints  = [[RTCMediaConstraints alloc] initWithMandatoryConstraints:mandatory

                                                                          optionalConstraints:nil];             return constraints;}