Matlab Simulink flip video vertically

I have made some modifications in original Simulink barcode recognition tool in order to make some research. It is necessary to scan some codes from smartphones as quickly as is it possible. Now it is very inconvenient to put device in proper position due to that video is displayed flipped vertically (not like in mirror). Is it possible to flip it one more time using only Simulink? I have tried to use negative scale but it is not working.

[Michal Szumski]

I have solved this problem. I've used "Matlab function" block from simulink/User-Defined Functions and wrote code inside:

function y = fcn(u)

y = flip(u,2);