This feature is made possible through a new API that Apple will introduce on iOS 13 that allows developers to implement the multi-cam feature into their app. The API itself was the result of the hardware pipeline revamp that Apple has performed on its devices in order to overcome the hardware limitation that prohibits multi-camera video capture on iOS devices.
According to the developer session earlier in the year at WWDC 2019, Apple is currently limiting the maximum amount of cameras that users can activate at the same time to two. However, it is not known whether such limitation is also applicable to the new iPhone 11 Pro since last week’s stage demo showed that the Filmic Pro is able to utilize all four cameras on the model. Meanwhile, do note that this multi-cam video capture is not a standard feature within iPhone’s native Camera app for the time being. In order to utilize it, you still need a third-party app that supports the related API. (Source: 9to5Mac)
