The creator of the program is being interviewed. He is talking about how he controls the way his program will appear to viewers. He says that when the program is presented on different devices (computers or television sets), the appearance may change due to different settings, such as brightness and contrast, that the viewer can change.
He simplifies his efforts to control the program's appearance by designing the program for Apple devices, because these are less adjustable than other devices.
In that sentence, "built in" has the same meaning as "dialled in". It means that Apple has predetermined the video settings and the viewer can't adjust them.