设备方向

/*
     UIDeviceOrientationUnknown,
     UIDeviceOrientationPortrait,            // 竖向-home键在下
     UIDeviceOrientationPortraitUpsideDown,  // 竖向-home键在上
     UIDeviceOrientationLandscapeLeft,       // 横向-home键在左
     UIDeviceOrientationFaceDown             // 横向-home键在右
     UIDeviceOrientationFaceUp,              // 平放-朝上
     UIDeviceOrientationFaceDown             // 平放-朝下
     */

    if ([connection isVideoOrientationSupported]){
        switch ([UIDevice currentDevice].orientation) {
            case UIInterfaceOrientationLandscapeLeft:
                connection.videoOrientation = AVCaptureVideoOrientationLandscapeLeft;
                break;
            case UIInterfaceOrientationLandscapeRight:
                connection.videoOrientation = AVCaptureVideoOrientationLandscapeRight;
                break;
            case UIInterfaceOrientationPortraitUpsideDown:
                connection.videoOrientation = AVCaptureVideoOrientationPortraitUpsideDown;
                break;
            case UIDeviceOrientationFaceDown:
                connection.videoOrientation = AVCaptureVideoOrientationPortraitUpsideDown;
                break;
            case UIDeviceOrientationFaceUp:
                connection.videoOrientation = UIDeviceOrientationLandscapeLeft;
                break;
            case UIDeviceOrientationPortrait:
                connection.videoOrientation = AVCaptureVideoOrientationPortrait;
                break;
            default:
                connection.videoOrientation = AVCaptureVideoOrientationPortrait;
                break;
    }